# CUPS Programming Manual

Michael R Sweet

Copyright © 2007-2018 by Apple Inc. All Rights Reserved.

## Contents

- Introduction
  - Guidelines
  - Terms Used in This Document
  - Compiling Programs That Use the CUPS API
- Working with Destinations
  - Finding Available Destinations
  - Basic Destination Information
  - Detailed Destination Information
  - Submitting a Print Job
- Sending IPP Requests
  - Connecting to the Scheduler or Printer
  - Creating an IPP Request
  - Sending the IPP Request
  - Processing the IPP Response
  - Authentication
- Functions
  - cupsAddDest
  - cupsAddDestMediaOptions
  - cupsAddIntegerOption
  - cupsAddOption
  - cupsCancelDestJob
  - cupsCheckDestSupported
  - cupsCloseDestJob
  - cupsConnectDest
  - cupsCopyDest
  - cupsCopyDestConflicts
  - cupsCopyDestInfo
  - cupsCreateDestJob
  - cupsDoAuthentication
  - cupsEncodeOption
  - cupsEncodeOptions
  - cupsEncodeOptions2
  - cupsEncryption
  - cupsEnumDests
  - cupsFindDestDefault
  - cupsFindDestReady
  - cupsFindDestSupported
  - cupsFinishDestDocument
  - cupsFreeDestInfo
  - cupsFreeDests
  - cupsFreeJobs
  - cupsFreeOptions
  - cupsGetDest
  - cupsGetDestMediaByIndex
  - cupsGetDestMediaByName
  - cupsGetDestMediaBySize
  - cupsGetDestMediaCount
  - cupsGetDestMediaDefault
  - cupsGetDestWithURI
  - cupsGetDests2
  - cupsGetIntegerOption
  - cupsGetJobs2
  - cupsGetNamedDest
  - cupsGetOption
  - cupsGetPassword2
  - cupsLocalizeDestMedia
  - cupsLocalizeDestOption
  - cupsLocalizeDestValue
  - cupsMakeServerCredentials
  - cupsParseOptions
  - cupsRemoveDest
  - cupsRemoveOption
  - cupsServer
  - cupsSetClientCertCB
  - cupsSetCredentials
  - cupsSetDefaultDest
  - cupsSetDests2
  - cupsSetEncryption
  - cupsSetPasswordCB2
  - cupsSetServer
  - cupsSetServerCertCB
  - cupsSetServerCredentials
  - cupsSetUser
  - cupsSetUserAgent
  - cupsStartDestDocument
  - cupsUser
  - cupsUserAgent
  - httpAcceptConnection
  - httpAddCredential
  - httpAddrAny
  - httpAddrClose
  - httpAddrConnect2
  - httpAddrCopyList
  - httpAddrEqual
  - httpAddrFamily
  - httpAddrFreeList
  - httpAddrGetList
  - httpAddrLength
  - httpAddrListen
  - httpAddrLocalhost
  - httpAddrLookup
  - httpAddrPort
  - httpAddrString
  - httpAssembleURI
  - httpAssembleURIf
  - httpAssembleUUID
  - httpBlocking
  - httpCheck
  - httpClearCookie
  - httpClearFields
  - httpClose
  - httpCompareCredentials
  - httpConnect2
  - httpCopyCredentials
  - httpCredentialsAreValidForName
  - httpCredentialsGetExpiration
  - httpCredentialsGetTrust
  - httpCredentialsString
  - httpDecode64_2
  - httpDelete
  - httpEncode64_2
  - httpEncryption
  - httpError
  - httpFieldValue
  - httpFlush
  - httpFlushWrite
  - httpFreeCredentials
  - httpGet
  - httpGetActivity
  - httpGetAddress
  - httpGetAuthString
  - httpGetBlocking
  - httpGetContentEncoding
  - httpGetCookie
  - httpGetDateString2
  - httpGetDateTime
  - httpGetEncryption
  - httpGetExpect
  - httpGetFd
  - httpGetField
  - httpGetHostname
  - httpGetKeepAlive
  - httpGetLength2
  - httpGetPending
  - httpGetReady
  - httpGetRemaining
  - httpGetState
  - httpGetStatus
  - httpGetSubField2
  - httpGetVersion
  - httpGets
  - httpHead
  - httpInitialize
  - httpIsChunked
  - httpIsEncrypted
  - httpLoadCredentials
  - httpOptions
  - httpPeek
  - httpPost
  - httpPut
  - httpRead2
  - httpReadRequest
  - httpReconnect2
  - httpResolveHostname
  - httpSaveCredentials
  - httpSeparateURI
  - httpSetAuthString
  - httpSetCookie
  - httpSetCredentials
  - httpSetDefaultField
  - httpSetExpect
  - httpSetField
  - httpSetKeepAlive
  - httpSetLength
  - httpSetTimeout
  - httpShutdown
  - httpStateString
  - httpStatus
  - httpURIStatusString
  - httpUpdate
  - httpWait
  - httpWrite2
  - httpWriteResponse
  - ippAddBoolean
  - ippAddBooleans
  - ippAddCollection
  - ippAddCollections
  - ippAddDate
  - ippAddInteger
  - ippAddIntegers
  - ippAddOctetString
  - ippAddOutOfBand
  - ippAddRange
  - ippAddRanges
  - ippAddResolution
  - ippAddResolutions
  - ippAddSeparator
  - ippAddString
  - ippAddStringf
  - ippAddStringfv
  - ippAddStrings
  - ippAttributeString
  - ippContainsInteger
  - ippContainsString
  - ippCopyAttribute
  - ippCopyAttributes
  - ippCreateRequestedArray
  - ippDateToTime
  - ippDelete
  - ippDeleteAttribute
  - ippDeleteValues
  - ippEnumString
  - ippEnumValue
  - ippErrorString
  - ippErrorValue
  - ippFindAttribute
  - ippFindNextAttribute
  - ippFirstAttribute
  - ippGetBoolean
  - ippGetCollection
  - ippGetCount
  - ippGetDate
  - ippGetGroupTag
  - ippGetInteger
  - ippGetName
  - ippGetOctetString
  - ippGetOperation
  - ippGetRange
  - ippGetRequestId
  - ippGetResolution
  - ippGetState
  - ippGetStatusCode
  - ippGetString
  - ippGetValueTag
  - ippGetVersion
  - ippLength
  - ippNew
  - ippNewRequest
  - ippNewResponse
  - ippNextAttribute
  - ippOpString
  - ippOpValue
  - ippPort
  - ippRead
  - ippReadFile
  - ippReadIO
  - ippSetBoolean
  - ippSetCollection
  - ippSetDate
  - ippSetGroupTag
  - ippSetInteger
  - ippSetName
  - ippSetOctetString
  - ippSetOperation
  - ippSetPort
  - ippSetRange
  - ippSetRequestId
  - ippSetResolution
  - ippSetState
  - ippSetStatusCode
  - ippSetString
  - ippSetStringf
  - ippSetStringfv
  - ippSetValueTag
  - ippSetVersion
  - ippStateString
  - ippTagString
  - ippTagValue
  - ippTimeToDate
  - ippValidateAttribute
  - ippValidateAttributes
  - ippWrite
  - ippWriteFile
  - ippWriteIO
- Data Types
  - cups_client_cert_cb_t
  - cups_dest_cb_t
  - cups_dest_t
  - cups_dinfo_t
  - cups_job_t
  - cups_option_t
  - cups_password_cb2_t
  - cups_ptype_t
  - cups_server_cert_cb_t
  - cups_size_t
  - http_addr_t
  - http_encoding_t
  - http_encryption_t
  - http_field_t
  - http_keepalive_t
  - http_state_t
  - http_t
  - http_timeout_cb_t
  - http_trust_t
  - http_uri_coding_t
  - http_uri_status_t
  - ipp_attribute_t
  - ipp_copycb_t
  - ipp_iocb_t
  - ipp_orient_t
  - ipp_pstate_t
  - ipp_quality_t
  - ipp_res_t
  - ipp_rstate_t
  - ipp_sstate_t
  - ipp_state_t
  - ipp_t
- Structures
  - cups_dest_s
  - cups_job_s
  - cups_option_s
  - cups_size_s
- Enumerations
  - cups_ptype_e
  - http_encoding_e
  - http_encryption_e
  - http_field_e
  - http_keepalive_e
  - http_state_e
  - http_status_e
  - http_trust_e
  - http_uri_coding_e
  - http_uri_status_e
  - ipp_finishings_e
  - ipp_jstate_e
  - ipp_op_e
  - ipp_orient_e
  - ipp_pstate_e
  - ipp_quality_e
  - ipp_res_e
  - ipp_rstate_e
  - ipp_sstate_e
  - ipp_state_e
  - ipp_status_e
  - ipp_tag_e

> Please file issues on Github to provide feedback on this document.

## Introduction

CUPS provides the "cups" library to talk to the different parts of CUPS and with Internet Printing Protocol (IPP) printers. The "cups" library functions are accessed by including the `<cups/cups.h>` header.

CUPS is based on the Internet Printing Protocol ("IPP"), which allows clients (applications) to communicate with a server (the scheduler, printers, etc.) to get a list of destinations, send print jobs, and so forth. You identify which server you want to communicate with using a pointer to the opaque structure `http_t`. The `CUPS_HTTP_DEFAULT` constant can be used when you want to talk to the CUPS scheduler.

### Guidelines

When writing software that uses the "cups" library:

- Do not use undocumented or deprecated APIs,
- Do not rely on pre-configured printers,
- Do not assume that printers support specific features or formats, and
- Do not rely on implementation details (PPDs, etc.)

CUPS is designed to insulate users and developers from the implementation details of printers and file formats. The goal is to allow an application to supply a print file in a standard format with the user intent ("print four copies, two-sided on A4 media, and staple each copy") and have the printing system manage the printer communication and format conversion needed.

Similarly, printer and job management applications can use standard query operations to obtain the status information in a common, generic form and use standard management operations to control the state of those printers and jobs.

### Terms Used in This Document

A Destination is a printer or print queue that accepts print jobs. A Print Job is one or more documents that are processed by a destination using options supplied when creating the job. A Document is a file (JPEG image, PDF file, etc.) suitable for printing. An Option controls some aspect of printing, such as the media used. Media is the sheets or roll that is printed on. An Attribute is an option encoded for an Internet Printing Protocol (IPP) request.

### Compiling Programs That Use the CUPS API

The CUPS libraries can be used from any C, C++, or Objective C program. The method of compiling against the libraries varies depending on the operating system and installation of CUPS. The following sections show how to compile a simple program (shown below) in two common environments.

The following simple program lists the available destinations:

    #include <stdio.h>
    #include <cups/cups.h>

    int print_dest(void *user_data, unsigned flags, cups_dest_t *dest)
    {
      if (dest->instance)
        printf("%s/%s\n", dest->name, dest->instance);
      else
        puts(dest->name);

      return (1);
    }

    int main(void)
    {
      cupsEnumDests(CUPS_DEST_FLAGS_NONE, 1000, NULL, 0, 0, print_dest, NULL);

      return (0);
    }

#### Compiling with Xcode

In Xcode, choose New Project... from the File menu (or press SHIFT+CMD+N), then select the Command Line Tool under the macOS Application project type. Click Next and enter a name for the project, for example "firstcups". Click Next and choose a project directory. The click Next to create the project.

In the project window, click on the Build Phases group and expand the Link Binary with Libraries section. Click +, type "libcups" to show the library, and then double-click on `libcups.tbd`.

Finally, click on the `main.c` file in the sidebar and copy the example program to the file. Build and run (CMD+R) to see the list of destinations.

#### Compiling with GCC

From the command-line, create a file called `sample.c` using your favorite editor, copy the example to this file, and save. Then run the following command to compile it with GCC and run it:

    gcc -o simple `cups-config --cflags` simple.c `cups-config --libs`
    ./simple

The `cups-config` command provides the compiler flags (`cups-config --cflags`) and libraries (`cups-config --libs`) needed for the local system.

## Working with Destinations

Destinations, which in CUPS represent individual printers or classes (collections or pools) of printers, are represented by the `cups_dest_t` structure which includes the name (`name`), instance (`instance`, saved options/settings), whether the destination is the default for the user (`is_default`), and the options and basic information associated with that destination (`num_options` and `options`).

Historically destinations have been manually maintained by the administrator of a system or network, but CUPS also supports dynamic discovery of destinations on the current network.

### Finding Available Destinations

The `cupsEnumDests` function finds all of the available destinations:

     int
     cupsEnumDests(unsigned flags, int msec, int *cancel,
                   cups_ptype_t type, cups_ptype_t mask,
                   cups_dest_cb_t cb, void *user_data)

The `flags` argument specifies enumeration options, which at present must be `CUPS_DEST_FLAGS_NONE`.

The `msec` argument specifies the maximum amount of time that should be used for enumeration in milliseconds - interactive applications should keep this value to 5000 or less when run on the main thread.

The `cancel` argument points to an integer variable that, when set to a non-zero value, will cause enumeration to stop as soon as possible. It can be `NULL` if not needed.

The `type` and `mask` arguments are bitfields that allow the caller to filter the destinations based on categories and/or capabilities. The destination's "printer-type" value is masked by the `mask` value and compared to the `type` value when filtering. For example, to only enumerate destinations that are hosted on the local system, pass `CUPS_PRINTER_LOCAL` for the `type` argument and `CUPS_PRINTER_DISCOVERED` for the `mask` argument. The following constants can be used for filtering:

- `CUPS_PRINTER_CLASS`: A collection of destinations.
- `CUPS_PRINTER_FAX`: A facsimile device.
- `CUPS_PRINTER_LOCAL`: A local printer or class. This constant has the value 0 (no bits set) and is only used for the `type` argument and is paired with the `CUPS_PRINTER_REMOTE` or `CUPS_PRINTER_DISCOVERED` constant passed in the `mask` argument.
- `CUPS_PRINTER_REMOTE`: A remote (shared) printer or class.
- `CUPS_PRINTER_DISCOVERED`: An available network printer or class.
- `CUPS_PRINTER_BW`: Can do B&W printing.
- `CUPS_PRINTER_COLOR`: Can do color printing.
- `CUPS_PRINTER_DUPLEX`: Can do two-sided printing.
- `CUPS_PRINTER_STAPLE`: Can staple output.
- `CUPS_PRINTER_COLLATE`: Can quickly collate copies.
- `CUPS_PRINTER_PUNCH`: Can punch output.
- `CUPS_PRINTER_COVER`: Can cover output.
- `CUPS_PRINTER_BIND`: Can bind output.
- `CUPS_PRINTER_SORT`: Can sort output (mailboxes, etc.)
- `CUPS_PRINTER_SMALL`: Can print on Letter/Legal/A4-size media.
- `CUPS_PRINTER_MEDIUM`: Can print on Tabloid/B/C/A3/A2-size media.
- `CUPS_PRINTER_LARGE`: Can print on D/E/A1/A0-size media.
- `CUPS_PRINTER_VARIABLE`: Can print on rolls and custom-size media.

The `cb` argument specifies a function to call for every destination that is found:

    typedef int (*cups_dest_cb_t)(void *user_data,
                                  unsigned flags,
                                  cups_dest_t *dest);

The callback function receives a copy of the `user_data` argument along with a bitfield (`flags`) and the destination that was found. The `flags` argument can have any of the following constant (bit) values set:

- `CUPS_DEST_FLAGS_MORE`: There are more destinations coming.
- `CUPS_DEST_FLAGS_REMOVED`: The destination has gone away and should be removed from the list of destinations a user can select.
- `CUPS_DEST_FLAGS_ERROR`: An error occurred. The reason for the error can be found by calling the `cupsLastError` and/or `cupsLastErrorString` functions.

The callback function returns 0 to stop enumeration or 1 to continue.

> Note that the callback function will likely be called multiple times for the same destination, so it is up to the caller to suppress any duplicate destinations.

The following example shows how to use `cupsEnumDests` to get a filtered array of destinations:

    typedef struct
    {
      int num_dests;
      cups_dest_t *dests;
    } my_user_data_t;

    int
    my_dest_cb(my_user_data_t *user_data, unsigned flags,
               cups_dest_t *dest)
    {
      if (flags & CUPS_DEST_FLAGS_REMOVED)
      {
       /*
        * Remove destination from array...
        */

        user_data->num_dests =
            cupsRemoveDest(dest->name, dest->instance,
                           user_data->num_dests,
                           &(user_data->dests));
      }
      else
      {
       /*
        * Add destination to array...
        */

        user_data->num_dests =
            cupsCopyDest(dest, user_data->num_dests,
                         &(user_data->dests));
      }

      return (1);
    }

    int
    my_get_dests(cups_ptype_t type, cups_ptype_t mask,
                 cups_dest_t **dests)
    {
      my_user_data_t user_data = { 0, NULL };

      if (!cupsEnumDests(CUPS_DEST_FLAGS_NONE, 1000, NULL, type,
                         mask, (cups_dest_cb_t)my_dest_cb,
                         &user_data))
      {
       /*
        * An error occurred, free all of the destinations and
        * return...
        */

        cupsFreeDests(user_data.num_dests, user_dasta.dests);

        *dests = NULL;

        return (0);
      }

     /*
      * Return the destination array...
      */

      *dests = user_data.dests;

      return (user_data.num_dests);
    }

### Basic Destination Information

The `num_options` and `options` members of the `cups_dest_t` structure provide basic attributes about the destination in addition to the user default options and values for that destination. The following names are predefined for various destination attributes:

- "auth-info-required": The type of authentication required for printing to this destination: "none", "username,password", "domain,username,password", or "negotiate" (Kerberos).
- "printer-info": The human-readable description of the destination such as "My Laser Printer".
- "printer-is-accepting-jobs": "true" if the destination is accepting new jobs, "false" otherwise.
- "printer-is-shared": "true" if the destination is being shared with other computers, "false" otherwise.
- "printer-location": The human-readable location of the destination such as "Lab 4".
- "printer-make-and-model": The human-readable make and model of the destination such as "ExampleCorp LaserPrinter 4000 Series".
- "printer-state": "3" if the destination is idle, "4" if the destination is printing a job, and "5" if the destination is stopped.
- "printer-state-change-time": The UNIX time when the destination entered the current state.
- "printer-state-reasons": Additional comma-delimited state keywords for the destination such as "media-tray-empty-error" and "toner-low-warning".
- "printer-type": The `cups_ptype_t` value associated with the destination.
- "printer-uri-supported": The URI associated with the destination; if not set, this destination was discovered but is not yet setup as a local printer.

Use the `cupsGetOption` function to retrieve the value. For example, the following code gets the make and model of a destination:

    const char *model = cupsGetOption("printer-make-and-model",
                                      dest->num_options,
                                      dest->options);

### Detailed Destination Information

Once a destination has been chosen, the `cupsCopyDestInfo` function can be used to gather detailed information about the destination:

    cups_dinfo_t *
    cupsCopyDestInfo(http_t *http, cups_dest_t *dest);

The `http` argument specifies a connection to the CUPS scheduler and is typically the constant `CUPS_HTTP_DEFAULT`. The `dest` argument specifies the destination to query.

The `cups_dinfo_t` structure that is returned contains a snapshot of the supported options and their supported, ready, and default values. It also can report constraints between different options and values, and recommend changes to resolve those constraints.

#### Getting Supported Options and Values

The `cupsCheckDestSupported` function can be used to test whether a particular option or option and value is supported:

    int
    cupsCheckDestSupported(http_t *http, cups_dest_t *dest,
                           cups_dinfo_t *info,
                           const char *option,
                           const char *value);

The `option` argument specifies the name of the option to check. The following constants can be used to check the various standard options:

- `CUPS_COPIES`: Controls the number of copies that are produced.
- `CUPS_FINISHINGS`: A comma-delimited list of integer constants that control the finishing processes that are applied to the job, including stapling, punching, and folding.
- `CUPS_MEDIA`: Controls the media size that is used, typically one of the following: `CUPS_MEDIA_3X5`, `CUPS_MEDIA_4X6`, `CUPS_MEDIA_5X7`, `CUPS_MEDIA_8X10`, `CUPS_MEDIA_A3`, `CUPS_MEDIA_A4`, `CUPS_MEDIA_A5`, `CUPS_MEDIA_A6`, `CUPS_MEDIA_ENV10`, `CUPS_MEDIA_ENVDL`, `CUPS_MEDIA_LEGAL`, `CUPS_MEDIA_LETTER`, `CUPS_MEDIA_PHOTO_L`, `CUPS_MEDIA_SUPERBA3`, or `CUPS_MEDIA_TABLOID`.
- `CUPS_MEDIA_SOURCE`: Controls where the media is pulled from, typically either `CUPS_MEDIA_SOURCE_AUTO` or `CUPS_MEDIA_SOURCE_MANUAL`.
- `CUPS_MEDIA_TYPE`: Controls the type of media that is used, typically one of the following: `CUPS_MEDIA_TYPE_AUTO`, `CUPS_MEDIA_TYPE_ENVELOPE`, `CUPS_MEDIA_TYPE_LABELS`, `CUPS_MEDIA_TYPE_LETTERHEAD`, `CUPS_MEDIA_TYPE_PHOTO`, `CUPS_MEDIA_TYPE_PHOTO_GLOSSY`, `CUPS_MEDIA_TYPE_PHOTO_MATTE`, `CUPS_MEDIA_TYPE_PLAIN`, or `CUPS_MEDIA_TYPE_TRANSPARENCY`.
- `CUPS_NUMBER_UP`: Controls the number of document pages that are placed on each media side.
- `CUPS_ORIENTATION`: Controls the orientation of document pages placed on the media: `CUPS_ORIENTATION_PORTRAIT` or `CUPS_ORIENTATION_LANDSCAPE`.
- `CUPS_PRINT_COLOR_MODE`: Controls whether the output is in color (`CUPS_PRINT_COLOR_MODE_COLOR`), grayscale (`CUPS_PRINT_COLOR_MODE_MONOCHROME`), or either (`CUPS_PRINT_COLOR_MODE_AUTO`).
- `CUPS_PRINT_QUALITY`: Controls the generate quality of the output: `CUPS_PRINT_QUALITY_DRAFT`, `CUPS_PRINT_QUALITY_NORMAL`, or `CUPS_PRINT_QUALITY_HIGH`.
- `CUPS_SIDES`: Controls whether prints are placed on one or both sides of the media: `CUPS_SIDES_ONE_SIDED`, `CUPS_SIDES_TWO_SIDED_PORTRAIT`, or `CUPS_SIDES_TWO_SIDED_LANDSCAPE`.

If the `value` argument is `NULL`, the `cupsCheckDestSupported` function returns whether the option is supported by the destination. Otherwise, the function returns whether the specified value of the option is supported.

The `cupsFindDestSupported` function returns the IPP attribute containing the supported values for a given option:

     ipp_attribute_t *
     cupsFindDestSupported(http_t *http, cups_dest_t *dest,
                           cups_dinfo_t *dinfo,
                           const char *option);

For example, the following code prints the supported finishing processes for a destination, if any, to the standard output:

    cups_dinfo_t *info = cupsCopyDestInfo(CUPS_HTTP_DEFAULT,
                                          dest);

    if (cupsCheckDestSupported(CUPS_HTTP_DEFAULT, dest, info,
                               CUPS_FINISHINGS, NULL))
    {
      ipp_attribute_t *finishings =
          cupsFindDestSupported(CUPS_HTTP_DEFAULT, dest, info,
                                CUPS_FINISHINGS);
      int i, count = ippGetCount(finishings);

      puts("finishings supported:");
      for (i = 0; i < count; i ++)
        printf("  %d\n", ippGetInteger(finishings, i));
    }
    else
      puts("finishings not supported.");

The "job-creation-attributes" option can be queried to get a list of supported options. For example, the following code prints the list of supported options to the standard output:

    ipp_attribute_t *attrs =
        cupsFindDestSupported(CUPS_HTTP_DEFAULT, dest, info,
                              "job-creation-attributes");
    int i, count = ippGetCount(attrs);

    for (i = 0; i < count; i ++)
      puts(ippGetString(attrs, i, NULL));

#### Getting Default Values

There are two sets of default values - user defaults that are available via the `num_options` and `options` members of the `cups_dest_t` structure, and destination defaults that available via the `cups_dinfo_t` structure and the `cupsFindDestDefault` function which returns the IPP attribute containing the default value(s) for a given option:

    ipp_attribute_t *
    cupsFindDestDefault(http_t *http, cups_dest_t *dest,
                        cups_dinfo_t *dinfo,
                        const char *option);

The user defaults from `cupsGetOption` should always take preference over the destination defaults. For example, the following code prints the default finishings value(s) to the standard output:

    const char *def_value =
        cupsGetOption(CUPS_FINISHINGS, dest->num_options,
                      dest->options);
    ipp_attribute_t *def_attr =
        cupsFindDestDefault(CUPS_HTTP_DEFAULT, dest, info,
                            CUPS_FINISHINGS);

    if (def_value != NULL)
    {
      printf("Default finishings: %s\n", def_value);
    }
    else
    {
      int i, count = ippGetCount(def_attr);

      printf("Default finishings: %d",
             ippGetInteger(def_attr, 0));
      for (i = 1; i < count; i ++)
        printf(",%d", ippGetInteger(def_attr, i));
      putchar('\n');
    }

#### Getting Ready (Loaded) Values

The finishings and media options also support queries for the ready, or loaded, values. For example, a printer may have punch and staple finishers installed but be out of staples - the supported values will list both punch and staple finishing processes but the ready values will only list the punch processes. Similarly, a printer may support hundreds of different sizes of media but only have a single size loaded at any given time - the ready values are limited to the media that is actually in the printer.

The `cupsFindDestReady` function finds the IPP attribute containing the ready values for a given option:

    ipp_attribute_t *
    cupsFindDestReady(http_t *http, cups_dest_t *dest,
                      cups_dinfo_t *dinfo, const char *option);

For example, the following code lists the ready finishing processes:

    ipp_attribute_t *ready_finishings =
        cupsFindDestReady(CUPS_HTTP_DEFAULT, dest, info,
                          CUPS_FINISHINGS);

    if (ready_finishings != NULL)
    {
      int i, count = ippGetCount(ready_finishings);

      puts("finishings ready:");
      for (i = 0; i < count; i ++)
        printf("  %d\n", ippGetInteger(ready_finishings, i));
    }
    else
      puts("no finishings are ready.");

#### Media Size Options

CUPS provides functions for querying the dimensions and margins for each of the supported media size options. The `cups_size_t` structure is used to describe a media size:

    typedef struct cups_size_s
    {
      char media[128];
      int width, length;
      int bottom, left, right, top;
    } cups_size_t;

The `width` and `length` members specify the dimensions of the media in hundredths of millimeters (1/2540th of an inch). The `bottom`, `left`, `right`, and `top` members specify the margins of the printable area, also in hundredths of millimeters.

The `cupsGetDestMediaByName` and `cupsGetDestMediaBySize` functions lookup the media size information using a standard media size name or dimensions in hundredths of millimeters:

    int
    cupsGetDestMediaByName(http_t *http, cups_dest_t *dest,
                           cups_dinfo_t *dinfo,
                           const char *media,
                           unsigned flags, cups_size_t *size);

    int
    cupsGetDestMediaBySize(http_t *http, cups_dest_t *dest,
                           cups_dinfo_t *dinfo,
                           int width, int length,
                           unsigned flags, cups_size_t *size);

The `media`, `width`, and `length` arguments specify the size to lookup. The `flags` argument specifies a bitfield controlling various lookup options:

- `CUPS_MEDIA_FLAGS_DEFAULT`: Find the closest size supported by the printer.
- `CUPS_MEDIA_FLAGS_BORDERLESS`: Find a borderless size.
- `CUPS_MEDIA_FLAGS_DUPLEX`: Find a size compatible with two-sided printing.
- `CUPS_MEDIA_FLAGS_EXACT`: Find an exact match for the size.
- `CUPS_MEDIA_FLAGS_READY`: If the printer supports media sensing or configuration of the media in each tray/source, find the size amongst the "ready" media.

If a matching size is found for the destination, the size information is stored in the structure pointed to by the `size` argument and 1 is returned. Otherwise 0 is returned.

For example, the following code prints the margins for two-sided printing on US Letter media:

    cups_size_t size;

    if (cupsGetDestMediaByName(CUPS_HTTP_DEFAULT, dest, info,
                               CUPS_MEDIA_LETTER,
                               CUPS_MEDIA_FLAGS_DUPLEX, &size))
    {
      puts("Margins for duplex US Letter:");
      printf("  Bottom: %.2fin\n", size.bottom / 2540.0);
      printf("    Left: %.2fin\n", size.left / 2540.0);
      printf("   Right: %.2fin\n", size.right / 2540.0);
      printf("     Top: %.2fin\n", size.top / 2540.0);
    }
    else
      puts("Margins for duplex US Letter are not available.");

You can also enumerate all of the sizes that match a given `flags` value using the `cupsGetDestMediaByIndex` and `cupsGetDestMediaCount` functions:

    int
    cupsGetDestMediaByIndex(http_t *http, cups_dest_t *dest,
                            cups_dinfo_t *dinfo, int n,
                            unsigned flags, cups_size_t *size);

    int
    cupsGetDestMediaCount(http_t *http, cups_dest_t *dest,
                          cups_dinfo_t *dinfo, unsigned flags);

For example, the following code prints the list of ready media and corresponding margins:

    cups_size_t size;
    int i;
    int count = cupsGetDestMediaCount(CUPS_HTTP_DEFAULT,
                                      dest, info,
                                      CUPS_MEDIA_FLAGS_READY);

    for (i = 0; i < count; i ++)
    {
      if (cupsGetDestMediaByIndex(CUPS_HTTP_DEFAULT, dest, info,
                                  i, CUPS_MEDIA_FLAGS_READY,
                                  &size))
      {
        printf("%s:\n", size.name);
        printf("   Width: %.2fin\n", size.width / 2540.0);
        printf("  Length: %.2fin\n", size.length / 2540.0);
        printf("  Bottom: %.2fin\n", size.bottom / 2540.0);
        printf("    Left: %.2fin\n", size.left / 2540.0);
        printf("   Right: %.2fin\n", size.right / 2540.0);
        printf("     Top: %.2fin\n", size.top / 2540.0);
      }
    }

Finally, the `cupsGetDestMediaDefault` function returns the default media size:

    int
    cupsGetDestMediaDefault(http_t *http, cups_dest_t *dest,
                            cups_dinfo_t *dinfo, unsigned flags,
                            cups_size_t *size);

#### Localizing Options and Values

CUPS provides three functions to get localized, human-readable strings in the user's current locale for options and values: `cupsLocalizeDestMedia`, `cupsLocalizeDestOption`, and `cupsLocalizeDestValue`:

    const char *
    cupsLocalizeDestMedia(http_t *http, cups_dest_t *dest,
                          cups_dinfo_t *info, unsigned flags,
                          cups_size_t *size);

    const char *
    cupsLocalizeDestOption(http_t *http, cups_dest_t *dest,
                           cups_dinfo_t *info,
                           const char *option);

    const char *
    cupsLocalizeDestValue(http_t *http, cups_dest_t *dest,
                          cups_dinfo_t *info,
                          const char *option, const char *value);

### Submitting a Print Job

Once you are ready to submit a print job, you create a job using the `cupsCreateDestJob` function:

    ipp_status_t
    cupsCreateDestJob(http_t *http, cups_dest_t *dest,
                      cups_dinfo_t *info, int *job_id,
                      const char *title, int num_options,
                      cups_option_t *options);

The `title` argument specifies a name for the print job such as "My Document". The `num_options` and `options` arguments specify the options for the print job which are allocated using the `cupsAddOption` function.

When successful, the job's numeric identifier is stored in the integer pointed to by the `job_id` argument and `IPP_STATUS_OK` is returned. Otherwise, an IPP error status is returned.

For example, the following code creates a new job that will print 42 copies of a two-sided US Letter document:

    int job_id = 0;
    int num_options = 0;
    cups_option_t *options = NULL;

    num_options = cupsAddOption(CUPS_COPIES, "42",
                                num_options, &options);
    num_options = cupsAddOption(CUPS_MEDIA, CUPS_MEDIA_LETTER,
                                num_options, &options);
    num_options = cupsAddOption(CUPS_SIDES,
                                CUPS_SIDES_TWO_SIDED_PORTRAIT,
                                num_options, &options);

    if (cupsCreateDestJob(CUPS_HTTP_DEFAULT, dest, info,
                          &job_id, "My Document", num_options,
                          options) == IPP_STATUS_OK)
      printf("Created job: %d\n", job_id);
    else
      printf("Unable to create job: %s\n",
             cupsLastErrorString());

Once the job is created, you submit documents for the job using the `cupsStartDestDocument`, `cupsWriteRequestData`, and `cupsFinishDestDocument` functions:

    http_status_t
    cupsStartDestDocument(http_t *http, cups_dest_t *dest,
                          cups_dinfo_t *info, int job_id,
                          const char *docname,
                          const char *format,
                          int num_options,
                          cups_option_t *options,
                          int last_document);

    http_status_t
    cupsWriteRequestData(http_t *http, const char *buffer,
                         size_t length);

    ipp_status_t
    cupsFinishDestDocument(http_t *http, cups_dest_t *dest,
                           cups_dinfo_t *info);

The `docname` argument specifies the name of the document, typically the original filename. The `format` argument specifies the MIME media type of the document, including the following constants:

- `CUPS_FORMAT_JPEG`: "image/jpeg"
- `CUPS_FORMAT_PDF`: "application/pdf"
- `CUPS_FORMAT_POSTSCRIPT`: "application/postscript"
- `CUPS_FORMAT_TEXT`: "text/plain"

The `num_options` and `options` arguments specify per-document print options, which at present must be 0 and `NULL`. The `last_document` argument specifies whether this is the last document in the job.

For example, the following code submits a PDF file to the job that was just created:

    FILE *fp = fopen("filename.pdf", "rb");
    size_t bytes;
    char buffer[65536];

    if (cupsStartDestDocument(CUPS_HTTP_DEFAULT, dest, info,
                              job_id, "filename.pdf", 0, NULL,
                              1) == HTTP_STATUS_CONTINUE)
    {
      while ((bytes = fread(buffer, 1, sizeof(buffer), fp)) > 0)
        if (cupsWriteRequestData(CUPS_HTTP_DEFAULT, buffer,
                                 bytes) != HTTP_STATUS_CONTINUE)
          break;

      if (cupsFinishDestDocument(CUPS_HTTP_DEFAULT, dest,
                                 info) == IPP_STATUS_OK)
        puts("Document send succeeded.");
      else
        printf("Document send failed: %s\n",
               cupsLastErrorString());
    }

    fclose(fp);

## Sending IPP Requests

CUPS provides a rich API for sending IPP requests to the scheduler or printers, typically from management or utility applications whose primary purpose is not to send print jobs.

### Connecting to the Scheduler or Printer

The connection to the scheduler or printer is represented by the HTTP connection type `http_t`. The `cupsConnectDest` function connects to the scheduler or printer associated with the destination:

    http_t *
    cupsConnectDest(cups_dest_t *dest, unsigned flags, int msec,
                    int *cancel, char *resource,
                    size_t resourcesize, cups_dest_cb_t cb,
                    void *user_data);

The `dest` argument specifies the destination to connect to.

The `flags` argument specifies whether you want to connect to the scheduler (`CUPS_DEST_FLAGS_NONE`) or device/printer (`CUPS_DEST_FLAGS_DEVICE`) associated with the destination.

The `msec` argument specifies how long you are willing to wait for the connection to be established in milliseconds. Specify a value of `-1` to wait indefinitely.

The `cancel` argument specifies the address of an integer variable that can be set to a non-zero value to cancel the connection. Specify a value of `NULL` to not provide a cancel variable.

The `resource` and `resourcesize` arguments specify the address and size of a character string array to hold the path to use when sending an IPP request.

The `cb` and `user_data` arguments specify a destination callback function that returns 1 to continue connecting or 0 to stop. The destination callback work the same way as the one used for the `cupsEnumDests` function.

On success, a HTTP connection is returned that can be used to send IPP requests and get IPP responses.

For example, the following code connects to the printer associated with a destination with a 30 second timeout:

    char resource[256];
    http_t *http = cupsConnectDest(dest, CUPS_DEST_FLAGS_DEVICE,
                                   30000, NULL, resource,
                                   sizeof(resource), NULL, NULL);

### Creating an IPP Request

IPP requests are represented by the IPP message type `ipp_t` and each IPP attribute in the request is representing using the type `ipp_attribute_t`. Each IPP request includes an operation code (`IPP_OP_CREATE_JOB`, `IPP_OP_GET_PRINTER_ATTRIBUTES`, etc.) and a 32-bit integer identifier.

The `ippNewRequest` function creates a new IPP request:

    ipp_t *
    ippNewRequest(ipp_op_t op);

The `op` argument specifies the IPP operation code for the request. For example, the following code creates an IPP Get-Printer-Attributes request:

    ipp_t *request = ippNewRequest(IPP_OP_GET_PRINTER_ATTRIBUTES);

The request identifier is automatically set to a unique value for the current process.

Each IPP request starts with two IPP attributes, "attributes-charset" and "attributes-natural-language", followed by IPP attribute(s) that specify the target of the operation. The `ippNewRequest` automatically adds the correct "attributes-charset" and "attributes-natural-language" attributes, but you must add the target attribute(s). For example, the following code adds the "printer-uri" attribute to the IPP Get-Printer-Attributes request to specify which printer is being queried:

    const char *printer_uri = cupsGetOption("device-uri",
                                            dest->num_options,
                                            dest->options);

    ippAddString(request, IPP_TAG_OPERATION, IPP_TAG_URI,
                 "printer-uri", NULL, printer_uri);

> Note: If we wanted to query the scheduler instead of the device, we would look up the "printer-uri-supported" option instead of the "device-uri" value.

The `ippAddString` function adds the "printer-uri" attribute the the IPP request. The `IPP_TAG_OPERATION` argument specifies that the attribute is part of the operation. The `IPP_TAG_URI` argument specifies that the value is a Universal Resource Identifier (URI) string. The `NULL` argument specifies there is no language (English, French, Japanese, etc.) associated with the string, and the `printer_uri` argument specifies the string value.

The IPP Get-Printer-Attributes request also supports an IPP attribute called "requested-attributes" that lists the attributes and values you are interested in. For example, the following code requests the printer state attributes:

    static const char * const requested_attributes[] =
    {
      "printer-state",
      "printer-state-message",
      "printer-state-reasons"
    };

    ippAddStrings(request, IPP_TAG_OPERATION, IPP_TAG_KEYWORD,
                  "requested-attributes", 3, NULL,
                  requested_attributes);

The `ippAddStrings` function adds an attribute with one or more strings, in this case three. The `IPP_TAG_KEYWORD` argument specifies that the strings are keyword values, which are used for attribute names. All strings use the same language (`NULL`), and the attribute will contain the three strings in the array `requested_attributes`.

CUPS provides many functions to adding attributes of different types:

- `ippAddBoolean` adds a boolean (`IPP_TAG_BOOLEAN`) attribute with one value.
- `ippAddInteger` adds an enum (`IPP_TAG_ENUM`) or integer (`IPP_TAG_INTEGER`) attribute with one value.
- `ippAddIntegers` adds an enum or integer attribute with one or more values.
- `ippAddOctetString` adds an octetString attribute with one value.
- `ippAddOutOfBand` adds a admin-defined (`IPP_TAG_ADMINDEFINE`), default (`IPP_TAG_DEFAULT`), delete-attribute (`IPP_TAG_DELETEATTR`), no-value (`IPP_TAG_NOVALUE`), not-settable (`IPP_TAG_NOTSETTABLE`), unknown (`IPP_TAG_UNKNOWN`), or unsupported (`IPP_TAG_UNSUPPORTED_VALUE`) out-of-band attribute.
- `ippAddRange` adds a rangeOfInteger attribute with one range.
- `ippAddRanges` adds a rangeOfInteger attribute with one or more ranges.
- `ippAddResolution` adds a resolution attribute with one resolution.
- `ippAddResolutions` adds a resolution attribute with one or more resolutions.
- `ippAddString` adds a charset (`IPP_TAG_CHARSET`), keyword (`IPP_TAG_KEYWORD`), mimeMediaType (`IPP_TAG_MIMETYPE`), name (`IPP_TAG_NAME` and `IPP_TAG_NAMELANG`), naturalLanguage (`IPP_TAG_NATURAL_LANGUAGE`), text (`IPP_TAG_TEXT` and `IPP_TAG_TEXTLANG`), uri (`IPP_TAG_URI`), or uriScheme (`IPP_TAG_URISCHEME`) attribute with one value.
- `ippAddStrings` adds a charset, keyword, mimeMediaType, name, naturalLanguage, text, uri, or uriScheme attribute with one or more values.

### Sending the IPP Request

Once you have created the IPP request, you can send it using the `cupsDoRequest` function. For example, the following code sends the IPP Get-Printer-Attributes request to the destination and saves the response:

    ipp_t *response = cupsDoRequest(http, request, resource);

For requests like Send-Document that include a file, the `cupsDoFileRequest` function should be used:

    ipp_t *response = cupsDoFileRequest(http, request, resource,
                                        filename);

Both `cupsDoRequest` and `cupsDoFileRequest` free the IPP request. If a valid IPP response is received, it is stored in a new IPP message (`ipp_t`) and returned to the caller. Otherwise `NULL` is returned.

The status from the most recent request can be queried using the `cupsLastError` function, for example:

    if (cupsLastError() >= IPP_STATUS_ERROR_BAD_REQUEST)
    {
      /* request failed */
    }

A human-readable error message is also available using the `cupsLastErrorString` function:

    if (cupsLastError() >= IPP_STATUS_ERROR_BAD_REQUEST)
    {
      /* request failed */
      printf("Request failed: %s\n", cupsLastErrorString());
    }

### Processing the IPP Response

Each response to an IPP request is also an IPP message (`ipp_t`) with its own IPP attributes (`ipp_attribute_t`) that includes a status code (`IPP_STATUS_OK`, `IPP_STATUS_ERROR_BAD_REQUEST`, etc.) and the corresponding 32-bit integer identifier from the request.

For example, the following code finds the printer state attributes and prints their values:

    ipp_attribute_t *attr;

    if ((attr = ippFindAttribute(response, "printer-state",
                                 IPP_TAG_ENUM)) != NULL)
    {
      printf("printer-state=%s\n",
             ippEnumString("printer-state", ippGetInteger(attr, 0)));
    }
    else
      puts("printer-state=unknown");

    if ((attr = ippFindAttribute(response, "printer-state-message",
                                 IPP_TAG_TEXT)) != NULL)
    {
      printf("printer-state-message=\"%s\"\n",
             ippGetString(attr, 0, NULL)));
    }

    if ((attr = ippFindAttribute(response, "printer-state-reasons",
                                 IPP_TAG_KEYWORD)) != NULL)
    {
      int i, count = ippGetCount(attr);

      puts("printer-state-reasons=");
      for (i = 0; i < count; i ++)
        printf("    %s\n", ippGetString(attr, i, NULL)));
    }

The `ippGetCount` function returns the number of values in an attribute.

The `ippGetInteger` and `ippGetString` functions return a single integer or string value from an attribute.

The `ippEnumString` function converts a enum value to its keyword (string) equivalent.

Once you are done using the IPP response message, free it using the `ippDelete` function:

    ippDelete(response);

### Authentication

CUPS normally handles authentication through the console. GUI applications should set a password callback using the `cupsSetPasswordCB2` function:

    void
    cupsSetPasswordCB2(cups_password_cb2_t cb, void *user_data);

The password callback will be called when needed and is responsible for setting the current user name using `cupsSetUser` and returning a string:

    const char *
    cups_password_cb2(const char *prompt, http_t *http,
                      const char *method, const char *resource,
                      void *user_data);

The `prompt` argument is a string from CUPS that should be displayed to the user.

The `http` argument is the connection hosting the request that is being authenticated. The password callback can call the `httpGetField` and `httpGetSubField` functions to look for additional details concerning the authentication challenge.

The `method` argument specifies the HTTP method used for the request and is typically "POST".

The `resource` argument specifies the path used for the request.

The `user_data` argument provides the user data pointer from the `cupsSetPasswordCB2` call.

## Functions

### cupsAddDest

Add a destination to the list of destinations.

int cupsAddDest(const char *name, const char *instance, int num_dests, cups_dest_t **dests);

#### Parameters

name | Destination name
instance | Instance name or `NULL` for none/primary
num_dests | Number of destinations
dests | Destinations

#### Return Value

New number of destinations

#### Discussion

This function cannot be used to add a new class or printer queue, it only adds a new container of saved options for the named destination or instance.
If the named destination already exists, the destination list is returned unchanged. Adding a new instance of a destination creates a copy of that destination's options.
Use the `cupsSaveDests` function to save the updated list of destinations to the user's lpoptions file.

### CUPS 2.3 cupsAddDestMediaOptions

Add the option corresponding to the specified media size.

int cupsAddDestMediaOptions(http_t *http, cups_dest_t *dest, cups_dinfo_t *dinfo, unsigned flags, cups_size_t *size, int num_options, cups_option_t **options);

#### Parameters

http | Connection to destination
dest | Destination
dinfo | Destination information
flags | Media matching flags
size | Media size
num_options | Current number of options
options | Options

#### Return Value

New number of options

### CUPS 2.2.4/macOS 10.13 cupsAddIntegerOption

Add an integer option to an option array.

int cupsAddIntegerOption(const char *name, int value, int num_options, cups_option_t **options);

#### Parameters

name | Name of option
value | Value of option
num_options | Number of options
options | Pointer to options

#### Return Value

Number of options

#### Discussion

New option arrays can be initialized simply by passing 0 for the "num_options" parameter.

### cupsAddOption

Add an option to an option array.

int cupsAddOption(const char *name, const char *value, int num_options, cups_option_t **options);

#### Parameters

name | Name of option
value | Value of option
num_options | Number of options
options | Pointer to options

#### Return Value

Number of options

#### Discussion

New option arrays can be initialized simply by passing 0 for the "num_options" parameter.

### CUPS 1.6/macOS 10.8 cupsCancelDestJob

Cancel a job on a destination.

ipp_status_t cupsCancelDestJob(http_t *http, cups_dest_t *dest, int job_id);

#### Parameters

http | Connection to destination
dest | Destination
job_id | Job ID

#### Return Value

Status of cancel operation

#### Discussion

The "job_id" is the number returned by cupsCreateDestJob.
Returns `IPP_STATUS_OK` on success and `IPP_STATUS_ERROR_NOT_AUTHORIZED` or `IPP_STATUS_ERROR_FORBIDDEN` on failure.

### CUPS 1.6/macOS 10.8 cupsCheckDestSupported

Check that the option and value are supported by the destination.

int cupsCheckDestSupported(http_t *http, cups_dest_t *dest, cups_dinfo_t *dinfo, const char *option, const char *value);

#### Parameters

http | Connection to destination
dest | Destination
dinfo | Destination information
option | Option
value | Value or `NULL`

#### Return Value

1 if supported, 0 otherwise

#### Discussion

Returns 1 if supported, 0 otherwise.

### CUPS 1.6/macOS 10.8 cupsCloseDestJob

Close a job and start printing.

ipp_status_t cupsCloseDestJob(http_t *http, cups_dest_t *dest, cups_dinfo_t *info, int job_id);

#### Parameters

http | Connection to destination
dest | Destination
info | Destination information
job_id | Job ID

#### Return Value

IPP status code

#### Discussion

Use when the last call to cupsStartDocument passed 0 for "last_document". "job_id" is the job ID returned by cupsCreateDestJob. Returns `IPP_STATUS_OK` on success.

### CUPS 1.6/macOS 10.8 cupsConnectDest

Open a connection to the destination.

http_t *cupsConnectDest(cups_dest_t *dest, unsigned flags, int msec, int *cancel, char *resource, size_t resourcesize, cups_dest_cb_t cb, void *user_data);

#### Parameters

dest | Destination
flags | Connection flags
msec | Timeout in milliseconds
cancel | Pointer to "cancel" variable
resource | Resource buffer
resourcesize | Size of resource buffer
cb | Callback function
user_data | User data pointer

#### Return Value

Connection to destination or `NULL`

#### Discussion

Connect to the destination, returning a new `http_t` connection object and optionally the resource path to use for the destination. These calls will block until a connection is made, the timeout expires, the integer pointed to by "cancel" is non-zero, or the callback function (or block) returns 0. The caller is responsible for calling `httpClose` on the returned connection.
Starting with CUPS 2.2.4, the caller can pass `CUPS_DEST_FLAGS_DEVICE` for the "flags" argument to connect directly to the device associated with the destination. Otherwise, the connection is made to the CUPS scheduler associated with the destination.

### CUPS 1.6/macOS 10.8 cupsCopyDest

Copy a destination.

int cupsCopyDest(cups_dest_t *dest, int num_dests, cups_dest_t **dests);

#### Parameters

dest | Destination to copy
num_dests | Number of destinations
dests | Destination array

#### Return Value

New number of destinations

#### Discussion

Make a copy of the destination to an array of destinations (or just a single copy) - for use with the cupsEnumDests* functions. The caller is responsible for calling cupsFreeDests() on the returned object(s).

### CUPS 1.6/macOS 10.8 cupsCopyDestConflicts

Get conflicts and resolutions for a new option/value pair.

int cupsCopyDestConflicts(http_t *http, cups_dest_t *dest, cups_dinfo_t *dinfo, int num_options, cups_option_t *options, const char *new_option, const char *new_value, int *num_conflicts, cups_option_t **conflicts, int *num_resolved, cups_option_t **resolved);

#### Parameters

http | Connection to destination
dest | Destination
dinfo | Destination information
num_options | Number of current options
options | Current options
new_option | New option
new_value | New value
num_conflicts | Number of conflicting options
conflicts | Conflicting options
num_resolved | Number of options to resolve
resolved | Resolved options

#### Return Value

1 if there is a conflict, 0 if none, -1 on error

#### Discussion

"num_options" and "options" represent the currently selected options by the user. "new_option" and "new_value" are the setting the user has just changed.
Returns 1 if there is a conflict, 0 if there are no conflicts, and -1 if there was an unrecoverable error such as a resolver loop.
If "num_conflicts" and "conflicts" are not `NULL`, they are set to contain the list of conflicting option/value pairs. Similarly, if "num_resolved" and "resolved" are not `NULL` they will be set to the list of changes needed to resolve the conflict.
If cupsCopyDestConflicts returns 1 but "num_resolved" and "resolved" are set to 0 and `NULL`, respectively, then the conflict cannot be resolved.

### CUPS 1.6/macOS 10.8 cupsCopyDestInfo

Get the supported values/capabilities for the destination.

cups_dinfo_t *cupsCopyDestInfo(http_t *http, cups_dest_t *dest);

#### Parameters

http | Connection to destination
dest | Destination

#### Return Value

Destination information

#### Discussion

The caller is responsible for calling `cupsFreeDestInfo` on the return value. `NULL` is returned on error.

### CUPS 1.6/macOS 10.8 cupsCreateDestJob

Create a job on a destination.

ipp_status_t cupsCreateDestJob(http_t *http, cups_dest_t *dest, cups_dinfo_t *info, int *job_id, const char *title, int num_options, cups_option_t *options);

#### Parameters

http | Connection to destination
dest | Destination
info | Destination information
job_id | Job ID or 0 on error
title | Job name
num_options | Number of job options
options | Job options

#### Return Value

IPP status code

#### Discussion

Returns `IPP_STATUS_OK` or `IPP_STATUS_OK_SUBST` on success, saving the job ID in the variable pointed to by "job_id".

### CUPS 1.1.20/macOS 10.4 cupsDoAuthentication

Authenticate a request.

int cupsDoAuthentication(http_t *http, const char *method, const char *resource);

#### Parameters

http | Connection to server or `CUPS_HTTP_DEFAULT`
method | Request method ("GET", "POST", "PUT")
resource | Resource path

#### Return Value

0 on success, -1 on error

#### Discussion

This function should be called in response to a `HTTP_STATUS_UNAUTHORIZED` status, prior to resubmitting your request.

### CUPS 2.3 cupsEncodeOption

Encode a single option into an IPP attribute.

ipp_attribute_t *cupsEncodeOption(ipp_t *ipp, ipp_tag_t group_tag, const char *name, const char *value);

#### Parameters

ipp | IPP request/response
group_tag | Attribute group
name | Option name
value | Option string value

#### Return Value

New attribute or `NULL` on error

### cupsEncodeOptions

Encode printer options into IPP attributes.

void cupsEncodeOptions(ipp_t *ipp, int num_options, cups_option_t *options);

#### Parameters

ipp | IPP request/response
num_options | Number of options
options | Options

#### Discussion

This function adds operation, job, and then subscription attributes, in that order. Use the `cupsEncodeOptions2` function to add attributes for a single group.

### CUPS 1.2/macOS 10.5 cupsEncodeOptions2

Encode printer options into IPP attributes for a group.

void cupsEncodeOptions2(ipp_t *ipp, int num_options, cups_option_t *options, ipp_tag_t group_tag);

#### Parameters

ipp | IPP request/response
num_options | Number of options
options | Options
group_tag | Group to encode

#### Discussion

This function only adds attributes for a single group. Call this function multiple times for each group, or use `cupsEncodeOptions` to add the standard groups.

### cupsEncryption

Get the current encryption settings.

http_encryption_t cupsEncryption(void);

#### Return Value

Encryption settings

#### Discussion

The default encryption setting comes from the CUPS_ENCRYPTION environment variable, then the ~/.cups/client.conf file, and finally the /etc/cups/client.conf file. If not set, the default is `HTTP_ENCRYPTION_IF_REQUESTED`.
Note: The current encryption setting is tracked separately for each thread in a program. Multi-threaded programs that override the setting via the `cupsSetEncryption` function need to do so in each thread for the same setting to be used.

### CUPS 1.6/macOS 10.8 cupsEnumDests

Enumerate available destinations with a callback function.

int cupsEnumDests(unsigned flags, int msec, int *cancel, cups_ptype_t type, cups_ptype_t mask, cups_dest_cb_t cb, void *user_data);

#### Parameters

flags | Enumeration flags
msec | Timeout in milliseconds, -1 for indefinite
cancel | Pointer to "cancel" variable
type | Printer type bits
mask | Mask for printer type bits
cb | Callback function
user_data | User data

#### Return Value

1 on success, 0 on failure

#### Discussion

Destinations are enumerated from one or more sources. The callback function receives the `user_data` pointer and the destination pointer which can be used as input to the `cupsCopyDest` function. The function must return 1 to continue enumeration or 0 to stop.
The `type` and `mask` arguments allow the caller to filter the destinations that are enumerated. Passing 0 for both will enumerate all printers. The constant `CUPS_PRINTER_DISCOVERED` is used to filter on destinations that are available but have not yet been added locally.
Enumeration happens on the current thread and does not return until all destinations have been enumerated or the callback function returns 0.
Note: The callback function will likely receive multiple updates for the same destinations - it is up to the caller to suppress any duplicate destinations.

### CUPS 1.7/macOS 10.9 cupsFindDestDefault

Find the default value(s) for the given option.

ipp_attribute_t *cupsFindDestDefault(http_t *http, cups_dest_t *dest, cups_dinfo_t *dinfo, const char *option);

#### Parameters

http | Connection to destination
dest | Destination
dinfo | Destination information
option | Option/attribute name

#### Return Value

Default attribute or `NULL` for none

#### Discussion

The returned value is an IPP attribute. Use the `ippGetBoolean`, `ippGetCollection`, `ippGetCount`, `ippGetDate`, `ippGetInteger`, `ippGetOctetString`, `ippGetRange`, `ippGetResolution`, `ippGetString`, and `ippGetValueTag` functions to inspect the default value(s) as needed.

### CUPS 1.7/macOS 10.9 cupsFindDestReady

Find the default value(s) for the given option.

ipp_attribute_t *cupsFindDestReady(http_t *http, cups_dest_t *dest, cups_dinfo_t *dinfo, const char *option);

#### Parameters

http | Connection to destination
dest | Destination
dinfo | Destination information
option | Option/attribute name

#### Return Value

Default attribute or `NULL` for none

#### Discussion

The returned value is an IPP attribute. Use the `ippGetBoolean`, `ippGetCollection`, `ippGetCount`, `ippGetDate`, `ippGetInteger`, `ippGetOctetString`, `ippGetRange`, `ippGetResolution`, `ippGetString`, and `ippGetValueTag` functions to inspect the default value(s) as needed.

### CUPS 1.7/macOS 10.9 cupsFindDestSupported

Find the default value(s) for the given option.

ipp_attribute_t *cupsFindDestSupported(http_t *http, cups_dest_t *dest, cups_dinfo_t *dinfo, const char *option);

#### Parameters

http | Connection to destination
dest | Destination
dinfo | Destination information
option | Option/attribute name

#### Return Value

Default attribute or `NULL` for none

#### Discussion

The returned value is an IPP attribute. Use the `ippGetBoolean`, `ippGetCollection`, `ippGetCount`, `ippGetDate`, `ippGetInteger`, `ippGetOctetString`, `ippGetRange`, `ippGetResolution`, `ippGetString`, and `ippGetValueTag` functions to inspect the default value(s) as needed.

### CUPS 1.6/macOS 10.8 cupsFinishDestDocument

Finish the current document.

ipp_status_t cupsFinishDestDocument(http_t *http, cups_dest_t *dest, cups_dinfo_t *info);

#### Parameters

http | Connection to destination
dest | Destination
info | Destination information

#### Return Value

Status of document submission

#### Discussion

Returns `IPP_STATUS_OK` or `IPP_STATUS_OK_SUBST` on success.

### CUPS 1.6/macOS 10.8 cupsFreeDestInfo

Free destination information obtained using `cupsCopyDestInfo`.

void cupsFreeDestInfo(cups_dinfo_t *dinfo);

#### Parameters

dinfo | Destination information

### cupsFreeDests

Free the memory used by the list of destinations.

void cupsFreeDests(int num_dests, cups_dest_t *dests);

#### Parameters

num_dests | Number of destinations
dests | Destinations

### cupsFreeJobs

Free memory used by job data.

void cupsFreeJobs(int num_jobs, cups_job_t *jobs);

#### Parameters

num_jobs | Number of jobs
jobs | Jobs

### cupsFreeOptions

Free all memory used by options.

void cupsFreeOptions(int num_options, cups_option_t *options);

#### Parameters

num_options | Number of options
options | Pointer to options

### cupsGetDest

Get the named destination from the list.

cups_dest_t *cupsGetDest(const char *name, const char *instance, int num_dests, cups_dest_t *dests);

#### Parameters

name | Destination name or `NULL` for the default destination
instance | Instance name or `NULL`
num_dests | Number of destinations
dests | Destinations

#### Return Value

Destination pointer or `NULL`

#### Discussion

Use the `cupsEnumDests` or `cupsGetDests2` functions to get a list of supported destinations for the current user.

### CUPS 1.7/macOS 10.9 cupsGetDestMediaByIndex

Get a media name, dimension, and margins for a specific size.

int cupsGetDestMediaByIndex(http_t *http, cups_dest_t *dest, cups_dinfo_t *dinfo, int n, unsigned flags, cups_size_t *size);

#### Parameters

http | Connection to destination
dest | Destination
dinfo | Destination information
n | Media size number (0-based)
flags | Media flags
size | Media size information

#### Return Value

1 on success, 0 on failure

#### Discussion

The `flags` parameter determines which set of media are indexed. For example, passing `CUPS_MEDIA_FLAGS_BORDERLESS` will get the Nth borderless size supported by the printer.

### CUPS 1.6/macOS 10.8 cupsGetDestMediaByName

Get media names, dimensions, and margins.

int cupsGetDestMediaByName(http_t *http, cups_dest_t *dest, cups_dinfo_t *dinfo, const char *media, unsigned flags, cups_size_t *size);

#### Parameters

http | Connection to destination
dest | Destination
dinfo | Destination information
media | Media name
flags | Media matching flags
size | Media size information

#### Return Value

1 on match, 0 on failure

#### Discussion

The "media" string is a PWG media name. "Flags" provides some matching guidance (multiple flags can be combined):
CUPS_MEDIA_FLAGS_DEFAULT = find the closest size supported by the printer, CUPS_MEDIA_FLAGS_BORDERLESS = find a borderless size, CUPS_MEDIA_FLAGS_DUPLEX = find a size compatible with 2-sided printing, CUPS_MEDIA_FLAGS_EXACT = find an exact match for the size, and CUPS_MEDIA_FLAGS_READY = if the printer supports media sensing, find the size amongst the "ready" media.
The matching result (if any) is returned in the "cups_size_t" structure.
Returns 1 when there is a match and 0 if there is not a match.

### CUPS 1.6/macOS 10.8 cupsGetDestMediaBySize

Get media names, dimensions, and margins.

int cupsGetDestMediaBySize(http_t *http, cups_dest_t *dest, cups_dinfo_t *dinfo, int width, int length, unsigned flags, cups_size_t *size);

#### Parameters

http | Connection to destination
dest | Destination
dinfo | Destination information
width | Media width in hundredths of of millimeters
length | Media length in hundredths of of millimeters
flags | Media matching flags
size | Media size information

#### Return Value

1 on match, 0 on failure

#### Discussion

"Width" and "length" are the dimensions in hundredths of millimeters. "Flags" provides some matching guidance (multiple flags can be combined):
CUPS_MEDIA_FLAGS_DEFAULT = find the closest size supported by the printer, CUPS_MEDIA_FLAGS_BORDERLESS = find a borderless size, CUPS_MEDIA_FLAGS_DUPLEX = find a size compatible with 2-sided printing, CUPS_MEDIA_FLAGS_EXACT = find an exact match for the size, and CUPS_MEDIA_FLAGS_READY = if the printer supports media sensing, find the size amongst the "ready" media.
The matching result (if any) is returned in the "cups_size_t" structure.
Returns 1 when there is a match and 0 if there is not a match.

### CUPS 1.7/macOS 10.9 cupsGetDestMediaCount

Get the number of sizes supported by a destination.

int cupsGetDestMediaCount(http_t *http, cups_dest_t *dest, cups_dinfo_t *dinfo, unsigned flags);

#### Parameters

http | Connection to destination
dest | Destination
dinfo | Destination information
flags | Media flags

#### Return Value

Number of sizes

#### Discussion

The `flags` parameter determines the set of media sizes that are counted. For example, passing `CUPS_MEDIA_FLAGS_BORDERLESS` will return the number of borderless sizes.

### CUPS 1.7/macOS 10.9 cupsGetDestMediaDefault

Get the default size for a destination.

int cupsGetDestMediaDefault(http_t *http, cups_dest_t *dest, cups_dinfo_t *dinfo, unsigned flags, cups_size_t *size);

#### Parameters

http | Connection to destination
dest | Destination
dinfo | Destination information
flags | Media flags
size | Media size information

#### Return Value

1 on success, 0 on failure

#### Discussion

The `flags` parameter determines which default size is returned. For example, passing `CUPS_MEDIA_FLAGS_BORDERLESS` will return the default borderless size, typically US Letter or A4, but sometimes 4x6 photo media.

### CUPS 2.0/macOS 10.10 cupsGetDestWithURI

Get a destination associated with a URI.

cups_dest_t *cupsGetDestWithURI(const char *name, const char *uri);

#### Parameters

name | Desired printer name or `NULL`
uri | URI for the printer

#### Return Value

Destination or `NULL`

#### Discussion

"name" is the desired name for the printer. If `NULL`, a name will be created using the URI.
"uri" is the "ipp" or "ipps" URI for the printer.

### CUPS 1.1.21/macOS 10.4 cupsGetDests2

Get the list of destinations from the specified server.

int cupsGetDests2(http_t *http, cups_dest_t **dests);

#### Parameters

http | Connection to server or `CUPS_HTTP_DEFAULT`
dests | Destinations

#### Return Value

Number of destinations

#### Discussion

Starting with CUPS 1.2, the returned list of destinations include the "printer-info", "printer-is-accepting-jobs", "printer-is-shared", "printer-make-and-model", "printer-state", "printer-state-change-time", "printer-state-reasons", "printer-type", and "printer-uri-supported" attributes as options.
CUPS 1.4 adds the "marker-change-time", "marker-colors", "marker-high-levels", "marker-levels", "marker-low-levels", "marker-message", "marker-names", "marker-types", and "printer-commands" attributes as options.
CUPS 2.2 adds accessible IPP printers to the list of destinations that can be used. The "printer-uri-supported" option will be present for those IPP printers that have been recently used.
Use the `cupsFreeDests` function to free the destination list and the `cupsGetDest` function to find a particular destination.

### CUPS 2.2.4/macOS 10.13 cupsGetIntegerOption

Get an integer option value.

int cupsGetIntegerOption(const char *name, int num_options, cups_option_t *options);

#### Parameters

name | Name of option
num_options | Number of options
options | Options

#### Return Value

Option value or `INT_MIN`

#### Discussion

INT_MIN is returned when the option does not exist, is not an integer, or exceeds the range of values for the "int" type.

### CUPS 1.1.21/macOS 10.4 cupsGetJobs2

Get the jobs from the specified server.

int cupsGetJobs2(http_t *http, cups_job_t **jobs, const char *name, int myjobs, int whichjobs);

#### Parameters

http | Connection to server or `CUPS_HTTP_DEFAULT`
jobs | Job data
name | `NULL` = all destinations, otherwise show jobs for named destination
myjobs | 0 = all users, 1 = mine
whichjobs | `CUPS_WHICHJOBS_ALL`, `CUPS_WHICHJOBS_ACTIVE`, or `CUPS_WHICHJOBS_COMPLETED`

#### Return Value

Number of jobs

#### Discussion

A "whichjobs" value of `CUPS_WHICHJOBS_ALL` returns all jobs regardless of state, while `CUPS_WHICHJOBS_ACTIVE` returns jobs that are pending, processing, or held and `CUPS_WHICHJOBS_COMPLETED` returns jobs that are stopped, canceled, aborted, or completed.

### CUPS 1.4/macOS 10.6 cupsGetNamedDest

Get options for the named destination.

cups_dest_t *cupsGetNamedDest(http_t *http, const char *name, const char *instance);

#### Parameters

http | Connection to server or `CUPS_HTTP_DEFAULT`
name | Destination name or `NULL` for the default destination
instance | Instance name or `NULL`

#### Return Value

Destination or `NULL`

#### Discussion

This function is optimized for retrieving a single destination and should be used instead of `cupsGetDests2` and `cupsGetDest` when you either know the name of the destination or want to print to the default destination. If `NULL` is returned, the destination does not exist or there is no default destination.
If "http" is `CUPS_HTTP_DEFAULT`, the connection to the default print server will be used.
If "name" is `NULL`, the default printer for the current user will be returned.
The returned destination must be freed using `cupsFreeDests` with a "num_dests" value of 1.

### cupsGetOption

Get an option value.

const char *cupsGetOption(const char *name, int num_options, cups_option_t *options);

#### Parameters

name | Name of option
num_options | Number of options
options | Options

#### Return Value

Option value or `NULL`

### CUPS 1.4/macOS 10.6 cupsGetPassword2

Get a password from the user using the current password callback.

const char *cupsGetPassword2(const char *prompt, http_t *http, const char *method, const char *resource);

#### Parameters

prompt | Prompt string
http | Connection to server or `CUPS_HTTP_DEFAULT`
method | Request method ("GET", "POST", "PUT")
resource | Resource path

#### Return Value

Password

#### Discussion

Uses the current password callback function. Returns `NULL` if the user does not provide a password.
Note: The current password callback function is tracked separately for each thread in a program. Multi-threaded programs that override the setting via the `cupsSetPasswordCB2` function need to do so in each thread for the same function to be used.

### CUPS 2.0/macOS 10.10 cupsLocalizeDestMedia

Get the localized string for a destination media size.

const char *cupsLocalizeDestMedia(http_t *http, cups_dest_t *dest, cups_dinfo_t *dinfo, unsigned flags, cups_size_t *size);

#### Parameters

http | Connection to destination
dest | Destination
dinfo | Destination information
flags | Media flags
size | Media size

#### Return Value

Localized string

#### Discussion

The returned string is stored in the destination information and will become invalid if the destination information is deleted.

### CUPS 1.6/macOS 10.8 cupsLocalizeDestOption

Get the localized string for a destination option.

const char *cupsLocalizeDestOption(http_t *http, cups_dest_t *dest, cups_dinfo_t *dinfo, const char *option);

#### Parameters

http | Connection to destination
dest | Destination
dinfo | Destination information
option | Option to localize

#### Return Value

Localized string

#### Discussion

The returned string is stored in the destination information and will become invalid if the destination information is deleted.

### CUPS 1.6/macOS 10.8 cupsLocalizeDestValue

Get the localized string for a destination option+value pair.

const char *cupsLocalizeDestValue(http_t *http, cups_dest_t *dest, cups_dinfo_t *dinfo, const char *option, const char *value);

#### Parameters

http | Connection to destination
dest | Destination
dinfo | Destination information
option | Option to localize
value | Value to localize

#### Return Value

Localized string

#### Discussion

The returned string is stored in the destination information and will become invalid if the destination information is deleted.

### CUPS 2.0/OS 10.10 cupsMakeServerCredentials

Make a self-signed certificate and private key pair.

int cupsMakeServerCredentials(const char *path, const char *common_name, int num_alt_names, const char **alt_names, time_t expiration_date);

#### Parameters

path | Keychain path or `NULL` for default
common_name | Common name
num_alt_names | Number of subject alternate names
alt_names | Subject Alternate Names
expiration_date | Expiration date

#### Return Value

1 on success, 0 on failure

### cupsParseOptions

Parse options from a command-line argument.

int cupsParseOptions(const char *arg, int num_options, cups_option_t **options);

#### Parameters

arg | Argument to parse
num_options | Number of options
options | Options found

#### Return Value

Number of options found

#### Discussion

This function converts space-delimited name/value pairs according to the PAPI text option ABNF specification. Collection values ("name={a=... b=... c=...}") are stored with the curley brackets intact - use `cupsParseOptions` on the value to extract the collection attributes.

### CUPS 1.3/macOS 10.5 cupsRemoveDest

Remove a destination from the destination list.

int cupsRemoveDest(const char *name, const char *instance, int num_dests, cups_dest_t **dests);

#### Parameters

name | Destination name
instance | Instance name or `NULL`
num_dests | Number of destinations
dests | Destinations

#### Return Value

New number of destinations

#### Discussion

Removing a destination/instance does not delete the class or printer queue, merely the lpoptions for that destination/instance. Use the `cupsSetDests` or `cupsSetDests2` functions to save the new options for the user.

### CUPS 1.2/macOS 10.5 cupsRemoveOption

Remove an option from an option array.

int cupsRemoveOption(const char *name, int num_options, cups_option_t **options);

#### Parameters

name | Option name
num_options | Current number of options
options | Options

#### Return Value

New number of options

### cupsServer

Return the hostname/address of the current server.

const char *cupsServer(void);

#### Return Value

Server name

#### Discussion

The default server comes from the CUPS_SERVER environment variable, then the ~/.cups/client.conf file, and finally the /etc/cups/client.conf file. If not set, the default is the local system - either "localhost" or a domain socket path.
The returned value can be a fully-qualified hostname, a numeric IPv4 or IPv6 address, or a domain socket pathname.
Note: The current server is tracked separately for each thread in a program. Multi-threaded programs that override the server via the `cupsSetServer` function need to do so in each thread for the same server to be used.

### CUPS 1.5/macOS 10.7 cupsSetClientCertCB

Set the client certificate callback.

void cupsSetClientCertCB(cups_client_cert_cb_t cb, void *user_data);

#### Parameters

cb | Callback function
user_data | User data pointer

#### Discussion

Pass `NULL` to restore the default callback.
Note: The current certificate callback is tracked separately for each thread in a program. Multi-threaded programs that override the callback need to do so in each thread for the same callback to be used.

### CUPS 1.5/macOS 10.7 cupsSetCredentials

Set the default credentials to be used for SSL/TLS connections.

int cupsSetCredentials(cups_array_t *credentials);

#### Parameters

credentials | Array of credentials

#### Return Value

Status of call (0 = success)

#### Discussion

Note: The default credentials are tracked separately for each thread in a program. Multi-threaded programs that override the setting need to do so in each thread for the same setting to be used.

### CUPS 1.3/macOS 10.5 cupsSetDefaultDest

Set the default destination.

void cupsSetDefaultDest(const char *name, const char *instance, int num_dests, cups_dest_t *dests);

#### Parameters

name | Destination name
instance | Instance name or `NULL`
num_dests | Number of destinations
dests | Destinations

### CUPS 1.1.21/macOS 10.4 cupsSetDests2

Save the list of destinations for the specified server.

int cupsSetDests2(http_t *http, int num_dests, cups_dest_t *dests);

#### Parameters

http | Connection to server or `CUPS_HTTP_DEFAULT`
num_dests | Number of destinations
dests | Destinations

#### Return Value

0 on success, -1 on error

#### Discussion

This function saves the destinations to /etc/cups/lpoptions when run as root and ~/.cups/lpoptions when run as a normal user.

### cupsSetEncryption

Set the encryption preference.

void cupsSetEncryption(http_encryption_t e);

#### Parameters

e | New encryption preference

#### Discussion

The default encryption setting comes from the CUPS_ENCRYPTION environment variable, then the ~/.cups/client.conf file, and finally the /etc/cups/client.conf file. If not set, the default is `HTTP_ENCRYPTION_IF_REQUESTED`.
Note: The current encryption setting is tracked separately for each thread in a program. Multi-threaded programs that override the setting need to do so in each thread for the same setting to be used.

### CUPS 1.4/macOS 10.6 cupsSetPasswordCB2

Set the advanced password callback for CUPS.

void cupsSetPasswordCB2(cups_password_cb2_t cb, void *user_data);

#### Parameters

cb | Callback function
user_data | User data pointer

#### Discussion

Pass `NULL` to restore the default (console) password callback, which reads the password from the console. Programs should call either this function or `cupsSetPasswordCB2`, as only one callback can be registered by a program per thread.
Note: The current password callback is tracked separately for each thread in a program. Multi-threaded programs that override the callback need to do so in each thread for the same callback to be used.

### cupsSetServer

Set the default server name and port.

void cupsSetServer(const char *server);

#### Parameters

server | Server name

#### Discussion

The "server" string can be a fully-qualified hostname, a numeric IPv4 or IPv6 address, or a domain socket pathname. Hostnames and numeric IP addresses can be optionally followed by a colon and port number to override the default port 631, e.g. "hostname:8631". Pass `NULL` to restore the default server name and port.
Note: The current server is tracked separately for each thread in a program. Multi-threaded programs that override the server need to do so in each thread for the same server to be used.

### CUPS 1.5/macOS 10.7 cupsSetServerCertCB

Set the server certificate callback.

void cupsSetServerCertCB(cups_server_cert_cb_t cb, void *user_data);

#### Parameters

cb | Callback function
user_data | User data pointer

#### Discussion

Pass `NULL` to restore the default callback.
Note: The current credentials callback is tracked separately for each thread in a program. Multi-threaded programs that override the callback need to do so in each thread for the same callback to be used.

### CUPS 2.0/macOS 10.10 cupsSetServerCredentials

Set the default server credentials.

int cupsSetServerCredentials(const char *path, const char *common_name, int auto_create);

#### Parameters

path | Keychain path or `NULL` for default
common_name | Default common name for server
auto_create | 1 = automatically create self-signed certificates

#### Return Value

1 on success, 0 on failure

#### Discussion

Note: The server credentials are used by all threads in the running process. This function is threadsafe.

### cupsSetUser

Set the default user name.

void cupsSetUser(const char *user);

#### Parameters

user | User name

#### Discussion

Pass `NULL` to restore the default user name.
Note: The current user name is tracked separately for each thread in a program. Multi-threaded programs that override the user name need to do so in each thread for the same user name to be used.

### CUPS 1.7/macOS 10.9 cupsSetUserAgent

Set the default HTTP User-Agent string.

void cupsSetUserAgent(const char *user_agent);

#### Parameters

user_agent | User-Agent string or `NULL`

#### Discussion

Setting the string to NULL forces the default value containing the CUPS version, IPP version, and operating system version and architecture.

### CUPS 1.6/macOS 10.8 cupsStartDestDocument

Start a new document.

http_status_t cupsStartDestDocument(http_t *http, cups_dest_t *dest, cups_dinfo_t *info, int job_id, const char *docname, const char *format, int num_options, cups_option_t *options, int last_document);

#### Parameters

http | Connection to destination
dest | Destination
info | Destination information
job_id | Job ID
docname | Document name
format | Document format
num_options | Number of document options
options | Document options
last_document | 1 if this is the last document

#### Return Value

Status of document creation

#### Discussion

"job_id" is the job ID returned by cupsCreateDestJob. "docname" is the name of the document/file being printed, "format" is the MIME media type for the document (see CUPS_FORMAT_xxx constants), and "num_options" and "options" are the options do be applied to the document. "last_document" should be 1 if this is the last document to be submitted in the job. Returns `HTTP_CONTINUE` on success.

### cupsUser

Return the current user's name.

const char *cupsUser(void);

#### Return Value

User name

#### Discussion

Note: The current user name is tracked separately for each thread in a program. Multi-threaded programs that override the user name with the `cupsSetUser` function need to do so in each thread for the same user name to be used.

### CUPS 1.7/macOS 10.9 cupsUserAgent

Return the default HTTP User-Agent string.

const char *cupsUserAgent(void);

#### Return Value

User-Agent string

### CUPS 1.7/macOS 10.9 httpAcceptConnection

Accept a new HTTP client connection from the specified listening socket.

http_t *httpAcceptConnection(int fd, int blocking);

#### Parameters

fd | Listen socket file descriptor
blocking | 1 if the connection should be blocking, 0 otherwise

#### Return Value

HTTP connection or `NULL`

### CUPS 1.5/macOS 10.7 httpAddCredential

Allocates and adds a single credential to an array.

int httpAddCredential(cups_array_t *credentials, const void *data, size_t datalen);

#### Parameters

credentials | Credentials array
data | PEM-encoded X.509 data
datalen | Length of data

#### Return Value

0 on success, -1 on error

#### Discussion

Use `cupsArrayNew(NULL, NULL)` to create a credentials array.

### CUPS 1.2/macOS 10.5 httpAddrAny

Check for the "any" address.

int httpAddrAny(const http_addr_t *addr);

#### Parameters

addr | Address to check

#### Return Value

1 if "any", 0 otherwise

### CUPS 2.0/OS 10.10 httpAddrClose

Close a socket created by `httpAddrConnect` or `httpAddrListen`.

int httpAddrClose(http_addr_t *addr, int fd);

#### Parameters

addr | Listen address or `NULL`
fd | Socket file descriptor

#### Return Value

0 on success, -1 on failure

#### Discussion

Pass `NULL` for sockets created with `httpAddrConnect2` and the listen address for sockets created with `httpAddrListen`. This function ensures that domain sockets are removed when closed.

### CUPS 1.7/macOS 10.9 httpAddrConnect2

Connect to any of the addresses in the list with a timeout and optional cancel.

http_addrlist_t *httpAddrConnect2(http_addrlist_t *addrlist, int *sock, int msec, int *cancel);

#### Parameters

addrlist | List of potential addresses
sock | Socket
msec | Timeout in milliseconds
cancel | Pointer to "cancel" variable

#### Return Value

Connected address or NULL on failure

### CUPS 1.7/macOS 10.9 httpAddrCopyList

Copy an address list.

http_addrlist_t *httpAddrCopyList(http_addrlist_t *src);

#### Parameters

src | Source address list

#### Return Value

New address list or `NULL` on error

### CUPS 1.2/macOS 10.5 httpAddrEqual

Compare two addresses.

int httpAddrEqual(const http_addr_t *addr1, const http_addr_t *addr2);

#### Parameters

addr1 | First address
addr2 | Second address

#### Return Value

1 if equal, 0 if not

### httpAddrFamily

Get the address family of an address.

int httpAddrFamily(http_addr_t *addr);

#### Parameters

addr | Address

#### Return Value

Address family

### CUPS 1.2/macOS 10.5 httpAddrFreeList

Free an address list.

void httpAddrFreeList(http_addrlist_t *addrlist);

#### Parameters

addrlist | Address list to free

### CUPS 1.2/macOS 10.5 httpAddrGetList

Get a list of addresses for a hostname.

http_addrlist_t *httpAddrGetList(const char *hostname, int family, const char *service);

#### Parameters

hostname | Hostname, IP address, or NULL for passive listen address
family | Address family or AF_UNSPEC
service | Service name or port number

#### Return Value

List of addresses or NULL

### CUPS 1.2/macOS 10.5 httpAddrLength

Return the length of the address in bytes.

int httpAddrLength(const http_addr_t *addr);

#### Parameters

addr | Address

#### Return Value

Length in bytes

### CUPS 1.7/macOS 10.9 httpAddrListen

Create a listening socket bound to the specified address and port.

int httpAddrListen(http_addr_t *addr, int port);

#### Parameters

addr | Address to bind to
port | Port number to bind to

#### Return Value

Socket or -1 on error

### CUPS 1.2/macOS 10.5 httpAddrLocalhost

Check for the local loopback address.

int httpAddrLocalhost(const http_addr_t *addr);

#### Parameters

addr | Address to check

#### Return Value

1 if local host, 0 otherwise

### CUPS 1.2/macOS 10.5 httpAddrLookup

Lookup the hostname associated with the address.

char *httpAddrLookup(const http_addr_t *addr, char *name, int namelen);

#### Parameters

addr | Address to lookup
name | Host name buffer
namelen | Size of name buffer

#### Return Value

Host name

### CUPS 1.7/macOS 10.9 httpAddrPort

Get the port number associated with an address.

int httpAddrPort(http_addr_t *addr);

#### Parameters

addr | Address

#### Return Value

Port number

### CUPS 1.2/macOS 10.5 httpAddrString

Convert an address to a numeric string.

char *httpAddrString(const http_addr_t *addr, char *s, int slen);

#### Parameters

addr | Address to convert
s | String buffer
slen | Length of string

#### Return Value

Numeric address string

### CUPS 1.2/macOS 10.5 httpAssembleURI

Assemble a uniform resource identifier from its components.

http_uri_status_t httpAssembleURI(http_uri_coding_t encoding, char *uri, int urilen, const char *scheme, const char *username, const char *host, int port, const char *resource);

#### Parameters

encoding | Encoding flags
uri | URI buffer
urilen | Size of URI buffer
scheme | Scheme name
username | Username
host | Hostname or address
port | Port number
resource | Resource

#### Return Value

URI status

#### Discussion

This function escapes reserved characters in the URI depending on the value of the "encoding" argument. You should use this function in place of traditional string functions whenever you need to create a URI string.

### CUPS 1.2/macOS 10.5 httpAssembleURIf

Assemble a uniform resource identifier from its components with a formatted resource.

http_uri_status_t httpAssembleURIf(http_uri_coding_t encoding, char *uri, int urilen, const char *scheme, const char *username, const char *host, int port, const char *resourcef, ...);

#### Parameters

encoding | Encoding flags
uri | URI buffer
urilen | Size of URI buffer
scheme | Scheme name
username | Username
host | Hostname or address
port | Port number
resourcef | Printf-style resource
... | Additional arguments as needed

#### Return Value

URI status

#### Discussion

This function creates a formatted version of the resource string argument "resourcef" and escapes reserved characters in the URI depending on the value of the "encoding" argument. You should use this function in place of traditional string functions whenever you need to create a URI string.

### CUPS 1.7/macOS 10.9 httpAssembleUUID

Assemble a name-based UUID URN conforming to RFC 4122.

char *httpAssembleUUID(const char *server, int port, const char *name, int number, char *buffer, size_t bufsize);

#### Parameters

server | Server name
port | Port number
name | Object name or NULL
number | Object number or 0
buffer | String buffer
bufsize | Size of buffer

#### Return Value

UUID string

#### Discussion

This function creates a unique 128-bit identifying number using the server name, port number, random data, and optionally an object name and/or object number. The result is formatted as a UUID URN as defined in RFC 4122.
The buffer needs to be at least 46 bytes in size.

### httpBlocking

Set blocking/non-blocking behavior on a connection.

void httpBlocking(http_t *http, int b);

#### Parameters

http | HTTP connection
b | 1 = blocking, 0 = non-blocking

### httpCheck

Check to see if there is a pending response from the server.

int httpCheck(http_t *http);

#### Parameters

http | HTTP connection

#### Return Value

0 = no data, 1 = data available

### CUPS 1.1.19/macOS 10.3 httpClearCookie

Clear the cookie value(s).

void httpClearCookie(http_t *http);

#### Parameters

http | HTTP connection

### httpClearFields

Clear HTTP request fields.

void httpClearFields(http_t *http);

#### Parameters

http | HTTP connection

### httpClose

Close an HTTP connection.

void httpClose(http_t *http);

#### Parameters

http | HTTP connection

### CUPS 2.0/OS 10.10 httpCompareCredentials

Compare two sets of X.509 credentials.

int httpCompareCredentials(cups_array_t *cred1, cups_array_t *cred2);

#### Parameters

cred1 | First set of X.509 credentials
cred2 | Second set of X.509 credentials

#### Return Value

1 if they match, 0 if they do not

### CUPS 1.7/macOS 10.9 httpConnect2

Connect to a HTTP server.

http_t *httpConnect2(const char *host, int port, http_addrlist_t *addrlist, int family, http_encryption_t encryption, int blocking, int msec, int *cancel);

#### Parameters

host | Host to connect to
port | Port number
addrlist | List of addresses or `NULL` to lookup
family | Address family to use or `AF_UNSPEC` for any
encryption | Type of encryption to use
blocking | 1 for blocking connection, 0 for non-blocking
msec | Connection timeout in milliseconds, 0 means don't connect
cancel | Pointer to "cancel" variable

#### Return Value

New HTTP connection

### CUPS 1.5/macOS 10.7 httpCopyCredentials

Copy the credentials associated with the peer in an encrypted connection.

int httpCopyCredentials(http_t *http, cups_array_t **credentials);

#### Parameters

http | Connection to server
credentials | Array of credentials

#### Return Value

Status of call (0 = success)

### CUPS 2.0/macOS 10.10 httpCredentialsAreValidForName

Return whether the credentials are valid for the given name.

int httpCredentialsAreValidForName(cups_array_t *credentials, const char *common_name);

#### Parameters

credentials | Credentials
common_name | Name to check

#### Return Value

1 if valid, 0 otherwise

### CUPS 2.0/macOS 10.10 httpCredentialsGetExpiration

Return the expiration date of the credentials.

time_t httpCredentialsGetExpiration(cups_array_t *credentials);

#### Parameters

credentials | Credentials

#### Return Value

Expiration date of credentials

### CUPS 2.0/macOS 10.10 httpCredentialsGetTrust

Return the trust of credentials.

http_trust_t httpCredentialsGetTrust(cups_array_t *credentials, const char *common_name);

#### Parameters

credentials | Credentials
common_name | Common name for trust lookup

#### Return Value

Level of trust

### CUPS 2.0/macOS 10.10 httpCredentialsString

Return a string representing the credentials.

size_t httpCredentialsString(cups_array_t *credentials, char *buffer, size_t bufsize);

#### Parameters

credentials | Credentials
buffer | Buffer or `NULL`
bufsize | Size of buffer

#### Return Value

Total size of credentials string

### CUPS 1.1.21/macOS 10.4 httpDecode64_2

Base64-decode a string.

char *httpDecode64_2(char *out, int *outlen, const char *in);

#### Parameters

out | String to write to
outlen | Size of output string
in | String to read from

#### Return Value

Decoded string

#### Discussion

The caller must initialize "outlen" to the maximum size of the decoded string before calling `httpDecode64_2`. On return "outlen" contains the decoded length of the string.

### httpDelete

Send a DELETE request to the server.

int httpDelete(http_t *http, const char *uri);

#### Parameters

http | HTTP connection
uri | URI to delete

#### Return Value

Status of call (0 = success)

### CUPS 1.1.21/macOS 10.4 httpEncode64_2

Base64-encode a string.

char *httpEncode64_2(char *out, int outlen, const char *in, int inlen);

#### Parameters

out | String to write to
outlen | Maximum size of output string
in | String to read from
inlen | Size of input string

#### Return Value

Encoded string

### httpEncryption

Set the required encryption on the link.

int httpEncryption(http_t *http, http_encryption_t e);

#### Parameters

http | HTTP connection
e | New encryption preference

#### Return Value

-1 on error, 0 on success

### httpError

Get the last error on a connection.

int httpError(http_t *http);

#### Parameters

http | HTTP connection

#### Return Value

Error code (errno) value

### httpFieldValue

Return the HTTP field enumeration value for a field name.

http_field_t httpFieldValue(const char *name);

#### Parameters

name | String name

#### Return Value

Field index

### httpFlush

Flush data read from a HTTP connection.

void httpFlush(http_t *http);

#### Parameters

http | HTTP connection

### CUPS 1.2/macOS 10.5 httpFlushWrite

Flush data written to a HTTP connection.

int httpFlushWrite(http_t *http);

#### Parameters

http | HTTP connection

#### Return Value

Bytes written or -1 on error

### httpFreeCredentials

Free an array of credentials.

void httpFreeCredentials(cups_array_t *credentials);

#### Parameters

credentials | Array of credentials

### httpGet

Send a GET request to the server.

int httpGet(http_t *http, const char *uri);

#### Parameters

http | HTTP connection
uri | URI to get

#### Return Value

Status of call (0 = success)

### CUPS 2.0/OS 10.10 httpGetActivity

Get the most recent activity for a connection.

time_t httpGetActivity(http_t *http);

#### Parameters

http | HTTP connection

#### Return Value

Time of last read or write

#### Discussion

The return value is the time in seconds of the last read or write.

### CUPS 2.0/OS 10.10 httpGetAddress

Get the address of the connected peer of a connection.

http_addr_t *httpGetAddress(http_t *http);

#### Parameters

http | HTTP connection

#### Return Value

Connected address or `NULL`

#### Discussion

For connections created with `httpConnect2`, the address is for the server. For connections created with `httpAccept`, the address is for the client.
Returns `NULL` if the socket is currently unconnected.

### CUPS 1.3/macOS 10.5 httpGetAuthString

Get the current authorization string.

char *httpGetAuthString(http_t *http);

#### Parameters

http | HTTP connection

#### Return Value

Authorization string

#### Discussion

The authorization string is set by `cupsDoAuthentication` and `httpSetAuthString`. Use `httpGetAuthString` to retrieve the string to use with `httpSetField` for the `HTTP_FIELD_AUTHORIZATION` value.

### CUPS 1.2/macOS 10.5 httpGetBlocking

Get the blocking/non-block state of a connection.

int httpGetBlocking(http_t *http);

#### Parameters

http | HTTP connection

#### Return Value

1 if blocking, 0 if non-blocking

### CUPS 1.7/macOS 10.9 httpGetContentEncoding

Get a common content encoding, if any, between the client and server.

const char *httpGetContentEncoding(http_t *http);

#### Parameters

http | HTTP connection

#### Return Value

Content-Coding value or `NULL` for the identity coding.

#### Discussion

This function uses the value of the Accepts-Encoding HTTP header and must be called after receiving a response from the server or a request from the client. The value returned can be use in subsequent requests (for clients) or in the response (for servers) in order to compress the content stream.

### CUPS 1.1.19/macOS 10.3 httpGetCookie

Get any cookie data from the response.

const char *httpGetCookie(http_t *http);

#### Parameters

http | HTTP connection

#### Return Value

Cookie data or `NULL`

### CUPS 1.2/macOS 10.5 httpGetDateString2

Get a formatted date/time string from a time value.

const char *httpGetDateString2(time_t t, char *s, int slen);

#### Parameters

t | Time in seconds
s | String buffer
slen | Size of string buffer

#### Return Value

Date/time string

### httpGetDateTime

Get a time value from a formatted date/time string.

time_t httpGetDateTime(const char *s);

#### Parameters

s | Date/time string

#### Return Value

Time in seconds

### CUPS 2.0/OS 10.10 httpGetEncryption

Get the current encryption mode of a connection.

http_encryption_t httpGetEncryption(http_t *http);

#### Parameters

http | HTTP connection

#### Return Value

Current encryption mode

#### Discussion

This function returns the encryption mode for the connection. Use the `httpIsEncrypted` function to determine whether a TLS session has been established.

### CUPS 1.7/macOS 10.9 httpGetExpect

Get the value of the Expect header, if any.

http_status_t httpGetExpect(http_t *http);

#### Parameters

http | HTTP connection

#### Return Value

Expect: status, if any

#### Discussion

Returns `HTTP_STATUS_NONE` if there is no Expect header, otherwise returns the expected HTTP status code, typically `HTTP_STATUS_CONTINUE`.

### CUPS 1.2/macOS 10.5 httpGetFd

Get the file descriptor associated with a connection.

int httpGetFd(http_t *http);

#### Parameters

http | HTTP connection

#### Return Value

File descriptor or -1 if none

### httpGetField

Get a field value from a request/response.

const char *httpGetField(http_t *http, http_field_t field);

#### Parameters

http | HTTP connection
field | Field to get

#### Return Value

Field value

### CUPS 1.2/macOS 10.5 httpGetHostname

Get the FQDN for the connection or local system.

const char *httpGetHostname(http_t *http, char *s, int slen);

#### Parameters

http | HTTP connection or NULL
s | String buffer for name
slen | Size of buffer

#### Return Value

FQDN for connection or system

#### Discussion

When "http" points to a connected socket, return the hostname or address that was used in the call to httpConnect() or httpConnectEncrypt(), or the address of the client for the connection from httpAcceptConnection(). Otherwise, return the FQDN for the local system using both gethostname() and gethostbyname() to get the local hostname with domain.

### CUPS 2.0/OS 10.10 httpGetKeepAlive

Get the current Keep-Alive state of the connection.

http_keepalive_t httpGetKeepAlive(http_t *http);

#### Parameters

http | HTTP connection

#### Return Value

Keep-Alive state

### CUPS 1.2/macOS 10.5 httpGetLength2

Get the amount of data remaining from the content-length or transfer-encoding fields.

off_t httpGetLength2(http_t *http);

#### Parameters

http | HTTP connection

#### Return Value

Content length

#### Discussion

This function returns the complete content length, even for content larger than 2^31 - 1.

### CUPS 2.0/OS 10.10 httpGetPending

Get the number of bytes that are buffered for writing.

size_t httpGetPending(http_t *http);

#### Parameters

http | HTTP connection

#### Return Value

Number of bytes buffered

### CUPS 2.0/OS 10.10 httpGetReady

Get the number of bytes that can be read without blocking.

size_t httpGetReady(http_t *http);

#### Parameters

http | HTTP connection

#### Return Value

Number of bytes available

### CUPS 2.0/OS 10.10 httpGetRemaining

Get the number of remaining bytes in the message body or current chunk.

size_t httpGetRemaining(http_t *http);

#### Parameters

http | HTTP connection

#### Return Value

Remaining bytes

#### Discussion

The `httpIsChunked` function can be used to determine whether the message body is chunked or fixed-length.

### httpGetState

Get the current state of the HTTP request.

http_state_t httpGetState(http_t *http);

#### Parameters

http | HTTP connection

#### Return Value

HTTP state

### CUPS 1.2/macOS 10.5 httpGetStatus

Get the status of the last HTTP request.

http_status_t httpGetStatus(http_t *http);

#### Parameters

http | HTTP connection

#### Return Value

HTTP status

### CUPS 1.2/macOS 10.5 httpGetSubField2

Get a sub-field value.

char *httpGetSubField2(http_t *http, http_field_t field, const char *name, char *value, int valuelen);

#### Parameters

http | HTTP connection
field | Field index
name | Name of sub-field
value | Value string
valuelen | Size of value buffer

#### Return Value

Value or `NULL`

### httpGetVersion

Get the HTTP version at the other end.

http_version_t httpGetVersion(http_t *http);

#### Parameters

http | HTTP connection

#### Return Value

Version number

### httpGets

Get a line of text from a HTTP connection.

char *httpGets(char *line, int length, http_t *http);

#### Parameters

line | Line to read into
length | Max length of buffer
http | HTTP connection

#### Return Value

Line or `NULL`

### httpHead

Send a HEAD request to the server.

int httpHead(http_t *http, const char *uri);

#### Parameters

http | HTTP connection
uri | URI for head

#### Return Value

Status of call (0 = success)

### httpInitialize

Initialize the HTTP interface library and set the default HTTP proxy (if any).

void httpInitialize(void);

### CUPS 2.0/OS 10.10 httpIsChunked

Report whether a message body is chunked.

int httpIsChunked(http_t *http);

#### Parameters

http | HTTP connection

#### Return Value

1 if chunked, 0 if not

#### Discussion

This function returns non-zero if the message body is composed of variable-length chunks.

### CUPS 2.0/OS 10.10 httpIsEncrypted

Report whether a connection is encrypted.

int httpIsEncrypted(http_t *http);

#### Parameters

http | HTTP connection

#### Return Value

1 if encrypted, 0 if not

#### Discussion

This function returns non-zero if the connection is currently encrypted.

### CUPS 2.0/OS 10.10 httpLoadCredentials

Load X.509 credentials from a keychain file.

int httpLoadCredentials(const char *path, cups_array_t **credentials, const char *common_name);

#### Parameters

path | Keychain path or `NULL` for default
credentials | Credentials
common_name | Common name for credentials

#### Return Value

0 on success, -1 on error

### httpOptions

Send an OPTIONS request to the server.

int httpOptions(http_t *http, const char *uri);

#### Parameters

http | HTTP connection
uri | URI for options

#### Return Value

Status of call (0 = success)

### CUPS 1.7/macOS 10.9 httpPeek

Peek at data from a HTTP connection.

ssize_t httpPeek(http_t *http, char *buffer, size_t length);

#### Parameters

http | HTTP connection
buffer | Buffer for data
length | Maximum number of bytes

#### Return Value

Number of bytes copied

#### Discussion

This function copies available data from the given HTTP connection, reading a buffer as needed. The data is still available for reading using `httpRead2`.
For non-blocking connections the usual timeouts apply.

### httpPost

Send a POST request to the server.

int httpPost(http_t *http, const char *uri);

#### Parameters

http | HTTP connection
uri | URI for post

#### Return Value

Status of call (0 = success)

### httpPut

Send a PUT request to the server.

int httpPut(http_t *http, const char *uri);

#### Parameters

http | HTTP connection
uri | URI to put

#### Return Value

Status of call (0 = success)

### CUPS 1.2/macOS 10.5 httpRead2

Read data from a HTTP connection.

ssize_t httpRead2(http_t *http, char *buffer, size_t length);

#### Parameters

http | HTTP connection
buffer | Buffer for data
length | Maximum number of bytes

#### Return Value

Number of bytes read

### CUPS 1.7/macOS 10.9 httpReadRequest

Read a HTTP request from a connection.

http_state_t httpReadRequest(http_t *http, char *uri, size_t urilen);

#### Parameters

http | HTTP connection
uri | URI buffer
urilen | Size of URI buffer

#### Return Value

New state of connection

### httpReconnect2

Reconnect to a HTTP server with timeout and optional cancel.

int httpReconnect2(http_t *http, int msec, int *cancel);

#### Parameters

http | HTTP connection
msec | Timeout in milliseconds
cancel | Pointer to "cancel" variable

#### Return Value

0 on success, non-zero on failure

### CUPS 2.0/OS 10.10 httpResolveHostname

Resolve the hostname of the HTTP connection address.

const char *httpResolveHostname(http_t *http, char *buffer, size_t bufsize);

#### Parameters

http | HTTP connection
buffer | Hostname buffer
bufsize | Size of buffer

#### Return Value

Resolved hostname or `NULL`

### CUPS 2.0/OS 10.10 httpSaveCredentials

Save X.509 credentials to a keychain file.

int httpSaveCredentials(const char *path, cups_array_t *credentials, const char *common_name);

#### Parameters

path | Keychain path or `NULL` for default
credentials | Credentials
common_name | Common name for credentials

#### Return Value

-1 on error, 0 on success

### CUPS 1.2/macOS 10.5 httpSeparateURI

Separate a Universal Resource Identifier into its components.

http_uri_status_t httpSeparateURI(http_uri_coding_t decoding, const char *uri, char *scheme, int schemelen, char *username, int usernamelen, char *host, int hostlen, int *port, char *resource, int resourcelen);

#### Parameters

decoding | Decoding flags
uri | Universal Resource Identifier
scheme | Scheme (http, https, etc.)
schemelen | Size of scheme buffer
username | Username
usernamelen | Size of username buffer
host | Hostname
hostlen | Size of hostname buffer
port | Port number to use
resource | Resource/filename
resourcelen | Size of resource buffer

#### Return Value

Result of separation

### CUPS 1.3/macOS 10.5 httpSetAuthString

Set the current authorization string.

void httpSetAuthString(http_t *http, const char *scheme, const char *data);

#### Parameters

http | HTTP connection
scheme | Auth scheme (NULL to clear it)
data | Auth data (NULL for none)

#### Discussion

This function just stores a copy of the current authorization string in the HTTP connection object. You must still call `httpSetField` to set `HTTP_FIELD_AUTHORIZATION` prior to issuing a HTTP request using `httpGet`, `httpHead`, `httpOptions`, `httpPost`, or `httpPut`.

### CUPS 1.1.19/macOS 10.3 httpSetCookie

Set the cookie value(s).

void httpSetCookie(http_t *http, const char *cookie);

#### Parameters

http | Connection
cookie | Cookie string

### CUPS 1.5/macOS 10.7 httpSetCredentials

Set the credentials associated with an encrypted connection.

int httpSetCredentials(http_t *http, cups_array_t *credentials);

#### Parameters

http | HTTP connection
credentials | Array of credentials

#### Return Value

Status of call (0 = success)

### CUPS 1.7/macOS 10.9 httpSetDefaultField

Set the default value of an HTTP header.

void httpSetDefaultField(http_t *http, http_field_t field, const char *value);

#### Parameters

http | HTTP connection
field | Field index
value | Value

#### Discussion

Currently only `HTTP_FIELD_ACCEPT_ENCODING`, `HTTP_FIELD_SERVER`, and `HTTP_FIELD_USER_AGENT` can be set.

### CUPS 1.2/macOS 10.5 httpSetExpect

Set the Expect: header in a request.

void httpSetExpect(http_t *http, http_status_t expect);

#### Parameters

http | HTTP connection
expect | HTTP status to expect (`HTTP_STATUS_CONTINUE`)

#### Discussion

Currently only `HTTP_STATUS_CONTINUE` is supported for the "expect" argument.

### httpSetField

Set the value of an HTTP header.

void httpSetField(http_t *http, http_field_t field, const char *value);

#### Parameters

http | HTTP connection
field | Field index
value | Value

### CUPS 2.0/OS 10.10 httpSetKeepAlive

Set the current Keep-Alive state of a connection.

void httpSetKeepAlive(http_t *http, http_keepalive_t keep_alive);

#### Parameters

http | HTTP connection
keep_alive | New Keep-Alive value

### CUPS 1.2/macOS 10.5 httpSetLength

Set the content-length and content-encoding.

void httpSetLength(http_t *http, size_t length);

#### Parameters

http | HTTP connection
length | Length (0 for chunked)

### CUPS 1.5/macOS 10.7 httpSetTimeout

Set read/write timeouts and an optional callback.

void httpSetTimeout(http_t *http, double timeout, http_timeout_cb_t cb, void *user_data);

#### Parameters

http | HTTP connection
timeout | Number of seconds for timeout, must be greater than 0
cb | Callback function or `NULL`
user_data | User data pointer

#### Discussion

The optional timeout callback receives both the HTTP connection and a user data pointer and must return 1 to continue or 0 to error (time) out.

### CUPS 2.0/OS 10.10 httpShutdown

Shutdown one side of an HTTP connection.

void httpShutdown(http_t *http);

#### Parameters

http | HTTP connection

### CUPS 2.0/OS 10.10 httpStateString

Return the string describing a HTTP state value.

const char *httpStateString(http_state_t state);

#### Parameters

state | HTTP state value

#### Return Value

State string

### httpStatus

Return a short string describing a HTTP status code.

const char *httpStatus(http_status_t status);

#### Parameters

status | HTTP status code

#### Return Value

Localized status string

#### Discussion

The returned string is localized to the current POSIX locale and is based on the status strings defined in RFC 7231.

### CUPS 2.0/OS 10.10 httpURIStatusString

Return a string describing a URI status code.

const char *httpURIStatusString(http_uri_status_t status);

#### Parameters

status | URI status code

#### Return Value

Localized status string

### httpUpdate

Update the current HTTP state for incoming data.

http_status_t httpUpdate(http_t *http);

#### Parameters

http | HTTP connection

#### Return Value

HTTP status

### CUPS 1.1.19/macOS 10.3 httpWait

Wait for data available on a connection.

int httpWait(http_t *http, int msec);

#### Parameters

http | HTTP connection
msec | Milliseconds to wait

#### Return Value

1 if data is available, 0 otherwise

### CUPS 1.2/macOS 10.5 httpWrite2

Write data to a HTTP connection.

ssize_t httpWrite2(http_t *http, const char *buffer, size_t length);

#### Parameters

http | HTTP connection
buffer | Buffer for data
length | Number of bytes to write

#### Return Value

Number of bytes written

### CUPS 1.7/macOS 10.9 httpWriteResponse

Write a HTTP response to a client connection.

int httpWriteResponse(http_t *http, http_status_t status);

#### Parameters

http | HTTP connection
status | Status code

#### Return Value

0 on success, -1 on error

### ippAddBoolean

Add a boolean attribute to an IPP message.

ipp_attribute_t *ippAddBoolean(ipp_t *ipp, ipp_tag_t group, const char *name, char value);

#### Parameters

ipp | IPP message
group | IPP group
name | Name of attribute
value | Value of attribute

#### Return Value

New attribute

#### Discussion

The `ipp` parameter refers to an IPP message previously created using the `ippNew`, `ippNewRequest`, or `ippNewResponse` functions.
The `group` parameter specifies the IPP attribute group tag: none (`IPP_TAG_ZERO`, for member attributes), document (`IPP_TAG_DOCUMENT`), event notification (`IPP_TAG_EVENT_NOTIFICATION`), operation (`IPP_TAG_OPERATION`), printer (`IPP_TAG_PRINTER`), subscription (`IPP_TAG_SUBSCRIPTION`), or unsupported (`IPP_TAG_UNSUPPORTED_GROUP`).

### ippAddBooleans

Add an array of boolean values.

ipp_attribute_t *ippAddBooleans(ipp_t *ipp, ipp_tag_t group, const char *name, int num_values, const char *values);

#### Parameters

ipp | IPP message
group | IPP group
name | Name of attribute
num_values | Number of values
values | Values

#### Return Value

New attribute

#### Discussion

The `ipp` parameter refers to an IPP message previously created using the `ippNew`, `ippNewRequest`, or `ippNewResponse` functions.
The `group` parameter specifies the IPP attribute group tag: none (`IPP_TAG_ZERO`, for member attributes), document (`IPP_TAG_DOCUMENT`), event notification (`IPP_TAG_EVENT_NOTIFICATION`), operation (`IPP_TAG_OPERATION`), printer (`IPP_TAG_PRINTER`), subscription (`IPP_TAG_SUBSCRIPTION`), or unsupported (`IPP_TAG_UNSUPPORTED_GROUP`).

### CUPS 1.1.19/macOS 10.3 ippAddCollection

Add a collection value.

ipp_attribute_t *ippAddCollection(ipp_t *ipp, ipp_tag_t group, const char *name, ipp_t *value);

#### Parameters

ipp | IPP message
group | IPP group
name | Name of attribute
value | Value

#### Return Value

New attribute

#### Discussion

The `ipp` parameter refers to an IPP message previously created using the `ippNew`, `ippNewRequest`, or `ippNewResponse` functions.
The `group` parameter specifies the IPP attribute group tag: none (`IPP_TAG_ZERO`, for member attributes), document (`IPP_TAG_DOCUMENT`), event notification (`IPP_TAG_EVENT_NOTIFICATION`), operation (`IPP_TAG_OPERATION`), printer (`IPP_TAG_PRINTER`), subscription (`IPP_TAG_SUBSCRIPTION`), or unsupported (`IPP_TAG_UNSUPPORTED_GROUP`).

### CUPS 1.1.19/macOS 10.3 ippAddCollections

Add an array of collection values.

ipp_attribute_t *ippAddCollections(ipp_t *ipp, ipp_tag_t group, const char *name, int num_values, const ipp_t **values);

#### Parameters

ipp | IPP message
group | IPP group
name | Name of attribute
num_values | Number of values
values | Values

#### Return Value

New attribute

#### Discussion

The `ipp` parameter refers to an IPP message previously created using the `ippNew`, `ippNewRequest`, or `ippNewResponse` functions.
The `group` parameter specifies the IPP attribute group tag: none (`IPP_TAG_ZERO`, for member attributes), document (`IPP_TAG_DOCUMENT`), event notification (`IPP_TAG_EVENT_NOTIFICATION`), operation (`IPP_TAG_OPERATION`), printer (`IPP_TAG_PRINTER`), subscription (`IPP_TAG_SUBSCRIPTION`), or unsupported (`IPP_TAG_UNSUPPORTED_GROUP`).

### ippAddDate

Add a dateTime attribute to an IPP message.

ipp_attribute_t *ippAddDate(ipp_t *ipp, ipp_tag_t group, const char *name, const ipp_uchar_t *value);

#### Parameters

ipp | IPP message
group | IPP group
name | Name of attribute
value | Value

#### Return Value

New attribute

#### Discussion

The `ipp` parameter refers to an IPP message previously created using the `ippNew`, `ippNewRequest`, or `ippNewResponse` functions.
The `group` parameter specifies the IPP attribute group tag: none (`IPP_TAG_ZERO`, for member attributes), document (`IPP_TAG_DOCUMENT`), event notification (`IPP_TAG_EVENT_NOTIFICATION`), operation (`IPP_TAG_OPERATION`), printer (`IPP_TAG_PRINTER`), subscription (`IPP_TAG_SUBSCRIPTION`), or unsupported (`IPP_TAG_UNSUPPORTED_GROUP`).

### ippAddInteger

Add a integer attribute to an IPP message.

ipp_attribute_t *ippAddInteger(ipp_t *ipp, ipp_tag_t group, ipp_tag_t value_tag, const char *name, int value);

#### Parameters

ipp | IPP message
group | IPP group
value_tag | Type of attribute
name | Name of attribute
value | Value of attribute

#### Return Value

New attribute

#### Discussion

The `ipp` parameter refers to an IPP message previously created using the `ippNew`, `ippNewRequest`, or `ippNewResponse` functions.
The `group` parameter specifies the IPP attribute group tag: none (`IPP_TAG_ZERO`, for member attributes), document (`IPP_TAG_DOCUMENT`), event notification (`IPP_TAG_EVENT_NOTIFICATION`), operation (`IPP_TAG_OPERATION`), printer (`IPP_TAG_PRINTER`), subscription (`IPP_TAG_SUBSCRIPTION`), or unsupported (`IPP_TAG_UNSUPPORTED_GROUP`).
Supported values include enum (`IPP_TAG_ENUM`) and integer (`IPP_TAG_INTEGER`).

### ippAddIntegers

Add an array of integer values.

ipp_attribute_t *ippAddIntegers(ipp_t *ipp, ipp_tag_t group, ipp_tag_t value_tag, const char *name, int num_values, const int *values);

#### Parameters

ipp | IPP message
group | IPP group
value_tag | Type of attribute
name | Name of attribute
num_values | Number of values
values | Values

#### Return Value

New attribute

#### Discussion

The `ipp` parameter refers to an IPP message previously created using the `ippNew`, `ippNewRequest`, or `ippNewResponse` functions.
The `group` parameter specifies the IPP attribute group tag: none (`IPP_TAG_ZERO`, for member attributes), document (`IPP_TAG_DOCUMENT`), event notification (`IPP_TAG_EVENT_NOTIFICATION`), operation (`IPP_TAG_OPERATION`), printer (`IPP_TAG_PRINTER`), subscription (`IPP_TAG_SUBSCRIPTION`), or unsupported (`IPP_TAG_UNSUPPORTED_GROUP`).
Supported values include enum (`IPP_TAG_ENUM`) and integer (`IPP_TAG_INTEGER`).

### CUPS 1.2/macOS 10.5 ippAddOctetString

Add an octetString value to an IPP message.

ipp_attribute_t *ippAddOctetString(ipp_t *ipp, ipp_tag_t group, const char *name, const void *data, int datalen);

#### Parameters

ipp | IPP message
group | IPP group
name | Name of attribute
data | octetString data
datalen | Length of data in bytes

#### Return Value

New attribute

#### Discussion

The `ipp` parameter refers to an IPP message previously created using the `ippNew`, `ippNewRequest`, or `ippNewResponse` functions.
The `group` parameter specifies the IPP attribute group tag: none (`IPP_TAG_ZERO`, for member attributes), document (`IPP_TAG_DOCUMENT`), event notification (`IPP_TAG_EVENT_NOTIFICATION`), operation (`IPP_TAG_OPERATION`), printer (`IPP_TAG_PRINTER`), subscription (`IPP_TAG_SUBSCRIPTION`), or unsupported (`IPP_TAG_UNSUPPORTED_GROUP`).

### CUPS 1.6/macOS 10.8 ippAddOutOfBand

Add an out-of-band value to an IPP message.

ipp_attribute_t *ippAddOutOfBand(ipp_t *ipp, ipp_tag_t group, ipp_tag_t value_tag, const char *name);

#### Parameters

ipp | IPP message
group | IPP group
value_tag | Type of attribute
name | Name of attribute

#### Return Value

New attribute

#### Discussion

The `ipp` parameter refers to an IPP message previously created using the `ippNew`, `ippNewRequest`, or `ippNewResponse` functions.
The `group` parameter specifies the IPP attribute group tag: none (`IPP_TAG_ZERO`, for member attributes), document (`IPP_TAG_DOCUMENT`), event notification (`IPP_TAG_EVENT_NOTIFICATION`), operation (`IPP_TAG_OPERATION`), printer (`IPP_TAG_PRINTER`), subscription (`IPP_TAG_SUBSCRIPTION`), or unsupported (`IPP_TAG_UNSUPPORTED_GROUP`).
Supported out-of-band values include unsupported-value (`IPP_TAG_UNSUPPORTED_VALUE`), default (`IPP_TAG_DEFAULT`), unknown (`IPP_TAG_UNKNOWN`), no-value (`IPP_TAG_NOVALUE`), not-settable (`IPP_TAG_NOTSETTABLE`), delete-attribute (`IPP_TAG_DELETEATTR`), and admin-define (`IPP_TAG_ADMINDEFINE`).

### ippAddRange

Add a range of values to an IPP message.

ipp_attribute_t *ippAddRange(ipp_t *ipp, ipp_tag_t group, const char *name, int lower, int upper);

#### Parameters

ipp | IPP message
group | IPP group
name | Name of attribute
lower | Lower value
upper | Upper value

#### Return Value

New attribute

#### Discussion

The `ipp` parameter refers to an IPP message previously created using the `ippNew`, `ippNewRequest`, or `ippNewResponse` functions.
The `group` parameter specifies the IPP attribute group tag: none (`IPP_TAG_ZERO`, for member attributes), document (`IPP_TAG_DOCUMENT`), event notification (`IPP_TAG_EVENT_NOTIFICATION`), operation (`IPP_TAG_OPERATION`), printer (`IPP_TAG_PRINTER`), subscription (`IPP_TAG_SUBSCRIPTION`), or unsupported (`IPP_TAG_UNSUPPORTED_GROUP`).
The `lower` parameter must be less than or equal to the `upper` parameter.

### ippAddRanges

Add ranges of values to an IPP message.

ipp_attribute_t *ippAddRanges(ipp_t *ipp, ipp_tag_t group, const char *name, int num_values, const int *lower, const int *upper);

#### Parameters

ipp | IPP message
group | IPP group
name | Name of attribute
num_values | Number of values
lower | Lower values
upper | Upper values

#### Return Value

New attribute

#### Discussion

The `ipp` parameter refers to an IPP message previously created using the `ippNew`, `ippNewRequest`, or `ippNewResponse` functions.
The `group` parameter specifies the IPP attribute group tag: none (`IPP_TAG_ZERO`, for member attributes), document (`IPP_TAG_DOCUMENT`), event notification (`IPP_TAG_EVENT_NOTIFICATION`), operation (`IPP_TAG_OPERATION`), printer (`IPP_TAG_PRINTER`), subscription (`IPP_TAG_SUBSCRIPTION`), or unsupported (`IPP_TAG_UNSUPPORTED_GROUP`).

### ippAddResolution

Add a resolution value to an IPP message.

ipp_attribute_t *ippAddResolution(ipp_t *ipp, ipp_tag_t group, const char *name, ipp_res_t units, int xres, int yres);

#### Parameters

ipp | IPP message
group | IPP group
name | Name of attribute
units | Units for resolution
xres | X resolution
yres | Y resolution

#### Return Value

New attribute

#### Discussion

The `ipp` parameter refers to an IPP message previously created using the `ippNew`, `ippNewRequest`, or `ippNewResponse` functions.
The `group` parameter specifies the IPP attribute group tag: none (`IPP_TAG_ZERO`, for member attributes), document (`IPP_TAG_DOCUMENT`), event notification (`IPP_TAG_EVENT_NOTIFICATION`), operation (`IPP_TAG_OPERATION`), printer (`IPP_TAG_PRINTER`), subscription (`IPP_TAG_SUBSCRIPTION`), or unsupported (`IPP_TAG_UNSUPPORTED_GROUP`).

### ippAddResolutions

Add resolution values to an IPP message.

ipp_attribute_t *ippAddResolutions(ipp_t *ipp, ipp_tag_t group, const char *name, int num_values, ipp_res_t units, const int *xres, const int *yres);

#### Parameters

ipp | IPP message
group | IPP group
name | Name of attribute
num_values | Number of values
units | Units for resolution
xres | X resolutions
yres | Y resolutions

#### Return Value

New attribute

#### Discussion

The `ipp` parameter refers to an IPP message previously created using the `ippNew`, `ippNewRequest`, or `ippNewResponse` functions.
The `group` parameter specifies the IPP attribute group tag: none (`IPP_TAG_ZERO`, for member attributes), document (`IPP_TAG_DOCUMENT`), event notification (`IPP_TAG_EVENT_NOTIFICATION`), operation (`IPP_TAG_OPERATION`), printer (`IPP_TAG_PRINTER`), subscription (`IPP_TAG_SUBSCRIPTION`), or unsupported (`IPP_TAG_UNSUPPORTED_GROUP`).

### ippAddSeparator

Add a group separator to an IPP message.

ipp_attribute_t *ippAddSeparator(ipp_t *ipp);

#### Parameters

ipp | IPP message

#### Return Value

New attribute

#### Discussion

The `ipp` parameter refers to an IPP message previously created using the `ippNew`, `ippNewRequest`, or `ippNewResponse` functions.

### ippAddString

Add a language-encoded string to an IPP message.

ipp_attribute_t *ippAddString(ipp_t *ipp, ipp_tag_t group, ipp_tag_t value_tag, const char *name, const char *language, const char *value);

#### Parameters

ipp | IPP message
group | IPP group
value_tag | Type of attribute
name | Name of attribute
language | Language code
value | Value

#### Return Value

New attribute

#### Discussion

The `ipp` parameter refers to an IPP message previously created using the `ippNew`, `ippNewRequest`, or `ippNewResponse` functions.
The `group` parameter specifies the IPP attribute group tag: none (`IPP_TAG_ZERO`, for member attributes), document (`IPP_TAG_DOCUMENT`), event notification (`IPP_TAG_EVENT_NOTIFICATION`), operation (`IPP_TAG_OPERATION`), printer (`IPP_TAG_PRINTER`), subscription (`IPP_TAG_SUBSCRIPTION`), or unsupported (`IPP_TAG_UNSUPPORTED_GROUP`).
Supported string values include charset (`IPP_TAG_CHARSET`), keyword (`IPP_TAG_KEYWORD`), language (`IPP_TAG_LANGUAGE`), mimeMediaType (`IPP_TAG_MIMETYPE`), name (`IPP_TAG_NAME`), nameWithLanguage (`IPP_TAG_NAMELANG), text (`code IPP_TAG_TEXT@), textWithLanguage (`IPP_TAG_TEXTLANG`), uri (`IPP_TAG_URI`), and uriScheme (`IPP_TAG_URISCHEME`).
The `language` parameter must be non-`NULL` for nameWithLanguage and textWithLanguage string values and must be `NULL` for all other string values.

### CUPS 1.7/macOS 10.9 ippAddStringf

Add a formatted string to an IPP message.

ipp_attribute_t *ippAddStringf(ipp_t *ipp, ipp_tag_t group, ipp_tag_t value_tag, const char *name, const char *language, const char *format, ...);

#### Parameters

ipp | IPP message
group | IPP group
value_tag | Type of attribute
name | Name of attribute
language | Language code (`NULL` for default)
format | Printf-style format string
... | Additional arguments as needed

#### Return Value

New attribute

#### Discussion

The `ipp` parameter refers to an IPP message previously created using the `ippNew`, `ippNewRequest`, or `ippNewResponse` functions.
The `group` parameter specifies the IPP attribute group tag: none (`IPP_TAG_ZERO`, for member attributes), document (`IPP_TAG_DOCUMENT`), event notification (`IPP_TAG_EVENT_NOTIFICATION`), operation (`IPP_TAG_OPERATION`), printer (`IPP_TAG_PRINTER`), subscription (`IPP_TAG_SUBSCRIPTION`), or unsupported (`IPP_TAG_UNSUPPORTED_GROUP`).
Supported string values include charset (`IPP_TAG_CHARSET`), keyword (`IPP_TAG_KEYWORD`), language (`IPP_TAG_LANGUAGE`), mimeMediaType (`IPP_TAG_MIMETYPE`), name (`IPP_TAG_NAME`), nameWithLanguage (`IPP_TAG_NAMELANG), text (`code IPP_TAG_TEXT@), textWithLanguage (`IPP_TAG_TEXTLANG`), uri (`IPP_TAG_URI`), and uriScheme (`IPP_TAG_URISCHEME`).
The `language` parameter must be non-`NULL` for nameWithLanguage and textWithLanguage string values and must be `NULL` for all other string values.
The `format` parameter uses formatting characters compatible with the printf family of standard functions. Additional arguments follow it as needed. The formatted string is truncated as needed to the maximum length of the corresponding value type.

### CUPS 1.7/macOS 10.9 ippAddStringfv

Add a formatted string to an IPP message.

ipp_attribute_t *ippAddStringfv(ipp_t *ipp, ipp_tag_t group, ipp_tag_t value_tag, const char *name, const char *language, const char *format, va_list ap);

#### Parameters

ipp | IPP message
group | IPP group
value_tag | Type of attribute
name | Name of attribute
language | Language code (`NULL` for default)
format | Printf-style format string
ap | Additional arguments

#### Return Value

New attribute

#### Discussion

The `ipp` parameter refers to an IPP message previously created using the `ippNew`, `ippNewRequest`, or `ippNewResponse` functions.
The `group` parameter specifies the IPP attribute group tag: none (`IPP_TAG_ZERO`, for member attributes), document (`IPP_TAG_DOCUMENT`), event notification (`IPP_TAG_EVENT_NOTIFICATION`), operation (`IPP_TAG_OPERATION`), printer (`IPP_TAG_PRINTER`), subscription (`IPP_TAG_SUBSCRIPTION`), or unsupported (`IPP_TAG_UNSUPPORTED_GROUP`).
Supported string values include charset (`IPP_TAG_CHARSET`), keyword (`IPP_TAG_KEYWORD`), language (`IPP_TAG_LANGUAGE`), mimeMediaType (`IPP_TAG_MIMETYPE`), name (`IPP_TAG_NAME`), nameWithLanguage (`IPP_TAG_NAMELANG), text (`code IPP_TAG_TEXT@), textWithLanguage (`IPP_TAG_TEXTLANG`), uri (`IPP_TAG_URI`), and uriScheme (`IPP_TAG_URISCHEME`).
The `language` parameter must be non-`NULL` for nameWithLanguage and textWithLanguage string values and must be `NULL` for all other string values.
The `format` parameter uses formatting characters compatible with the printf family of standard functions. Additional arguments are passed in the stdarg pointer `ap`. The formatted string is truncated as needed to the maximum length of the corresponding value type.

### ippAddStrings

Add language-encoded strings to an IPP message.

ipp_attribute_t *ippAddStrings(ipp_t *ipp, ipp_tag_t group, ipp_tag_t value_tag, const char *name, int num_values, const char *language, const char *const *values);

#### Parameters

ipp | IPP message
group | IPP group
value_tag | Type of attribute
name | Name of attribute
num_values | Number of values
language | Language code (`NULL` for default)
values | Values

#### Return Value

New attribute

#### Discussion

The `ipp` parameter refers to an IPP message previously created using the `ippNew`, `ippNewRequest`, or `ippNewResponse` functions.
The `group` parameter specifies the IPP attribute group tag: none (`IPP_TAG_ZERO`, for member attributes), document (`IPP_TAG_DOCUMENT`), event notification (`IPP_TAG_EVENT_NOTIFICATION`), operation (`IPP_TAG_OPERATION`), printer (`IPP_TAG_PRINTER`), subscription (`IPP_TAG_SUBSCRIPTION`), or unsupported (`IPP_TAG_UNSUPPORTED_GROUP`).
Supported string values include charset (`IPP_TAG_CHARSET`), keyword (`IPP_TAG_KEYWORD`), language (`IPP_TAG_LANGUAGE`), mimeMediaType (`IPP_TAG_MIMETYPE`), name (`IPP_TAG_NAME`), nameWithLanguage (`IPP_TAG_NAMELANG), text (`code IPP_TAG_TEXT@), textWithLanguage (`IPP_TAG_TEXTLANG`), uri (`IPP_TAG_URI`), and uriScheme (`IPP_TAG_URISCHEME`).
The `language` parameter must be non-`NULL` for nameWithLanguage and textWithLanguage string values and must be `NULL` for all other string values.

### CUPS 1.6/macOS 10.8 ippAttributeString

Convert the attribute's value to a string.

size_t ippAttributeString(ipp_attribute_t *attr, char *buffer, size_t bufsize);

#### Parameters

attr | Attribute
buffer | String buffer or NULL
bufsize | Size of string buffer

#### Return Value

Number of bytes less nul

#### Discussion

Returns the number of bytes that would be written, not including the trailing nul. The buffer pointer can be NULL to get the required length, just like (v)snprintf.

### CUPS 1.7/macOS 10.9 ippContainsInteger

Determine whether an attribute contains the specified value or is within the list of ranges.

int ippContainsInteger(ipp_attribute_t *attr, int value);

#### Parameters

attr | Attribute
value | Integer/enum value

#### Return Value

1 on a match, 0 on no match

#### Discussion

Returns non-zero when the attribute contains either a matching integer or enum value, or the value falls within one of the rangeOfInteger values for the attribute.

### CUPS 1.7/macOS 10.9 ippContainsString

Determine whether an attribute contains the specified string value.

int ippContainsString(ipp_attribute_t *attr, const char *value);

#### Parameters

attr | Attribute
value | String value

#### Return Value

1 on a match, 0 on no match

#### Discussion

Returns non-zero when the attribute contains a matching charset, keyword, naturalLanguage, mimeMediaType, name, text, uri, or uriScheme value.

### CUPS 1.6/macOS 10.8 ippCopyAttribute

Copy an attribute.

ipp_attribute_t *ippCopyAttribute(ipp_t *dst, ipp_attribute_t *srcattr, int quickcopy);

#### Parameters

dst | Destination IPP message
srcattr | Attribute to copy
quickcopy | 1 for a referenced copy, 0 for normal

#### Return Value

New attribute

#### Discussion

The specified attribute, `attr`, is copied to the destination IPP message. When `quickcopy` is non-zero, a "shallow" reference copy of the attribute is created - this should only be done as long as the original source IPP message will not be freed for the life of the destination.

### CUPS 1.6/macOS 10.8 ippCopyAttributes

Copy attributes from one IPP message to another.

int ippCopyAttributes(ipp_t *dst, ipp_t *src, int quickcopy, ipp_copycb_t cb, void *context);

#### Parameters

dst | Destination IPP message
src | Source IPP message
quickcopy | 1 for a referenced copy, 0 for normal
cb | Copy callback or `NULL` for none
context | Context pointer

#### Return Value

1 on success, 0 on error

#### Discussion

Zero or more attributes are copied from the source IPP message, `src`, to the destination IPP message, `dst`. When `quickcopy` is non-zero, a "shallow" reference copy of the attribute is created - this should only be done as long as the original source IPP message will not be freed for the life of the destination.
The `cb` and `context` parameters provide a generic way to "filter" the attributes that are copied - the function must return 1 to copy the attribute or 0 to skip it. The function may also choose to do a partial copy of the source attribute itself.

### CUPS 1.7/macOS 10.9 ippCreateRequestedArray

Create a CUPS array of attribute names from the given requested-attributes attribute.

cups_array_t *ippCreateRequestedArray(ipp_t *request);

#### Parameters

request | IPP request

#### Return Value

CUPS array or `NULL` if all

#### Discussion

This function creates a (sorted) CUPS array of attribute names matching the list of "requested-attribute" values supplied in an IPP request. All IANA- registered values are supported in addition to the CUPS IPP extension attributes.
The `request` parameter specifies the request message that was read from the client. `NULL` is returned if all attributes should be returned. Otherwise, the result is a sorted array of attribute names, where `cupsArrayFind(array, "attribute-name")` will return a non-NULL pointer. The array must be freed using the `cupsArrayDelete` function.

### ippDateToTime

Convert from RFC 2579 Date/Time format to time in seconds.

time_t ippDateToTime(const ipp_uchar_t *date);

#### Parameters

date | RFC 2579 date info

#### Return Value

UNIX time value

### ippDelete

Delete an IPP message.

void ippDelete(ipp_t *ipp);

#### Parameters

ipp | IPP message

### CUPS 1.1.19/macOS 10.3 ippDeleteAttribute

Delete a single attribute in an IPP message.

void ippDeleteAttribute(ipp_t *ipp, ipp_attribute_t *attr);

#### Parameters

ipp | IPP message
attr | Attribute to delete

### CUPS 1.6/macOS 10.8 ippDeleteValues

Delete values in an attribute.

int ippDeleteValues(ipp_t *ipp, ipp_attribute_t **attr, int element, int count);

#### Parameters

ipp | IPP message
attr | Attribute
element | Index of first value to delete (0-based)
count | Number of values to delete

#### Return Value

1 on success, 0 on failure

#### Discussion

The `element` parameter specifies the first value to delete, starting at 0. It must be less than the number of values returned by `ippGetCount`.
The `attr` parameter may be modified as a result of setting the value.
Deleting all values in an attribute deletes the attribute.

### ippEnumString

Return a string corresponding to the enum value.

const char *ippEnumString(const char *attrname, int enumvalue);

#### Parameters

attrname | Attribute name
enumvalue | Enum value

#### Return Value

Enum string

### ippEnumValue

Return the value associated with a given enum string.

int ippEnumValue(const char *attrname, const char *enumstring);

#### Parameters

attrname | Attribute name
enumstring | Enum string

#### Return Value

Enum value or -1 if unknown

### ippErrorString

Return a name for the given status code.

const char *ippErrorString(ipp_status_t error);

#### Parameters

error | Error status

#### Return Value

Text string

### CUPS 1.2/macOS 10.5 ippErrorValue

Return a status code for the given name.

ipp_status_t ippErrorValue(const char *name);

#### Parameters

name | Name

#### Return Value

IPP status code

### ippFindAttribute

Find a named attribute in a request.

ipp_attribute_t *ippFindAttribute(ipp_t *ipp, const char *name, ipp_tag_t type);

#### Parameters

ipp | IPP message
name | Name of attribute
type | Type of attribute

#### Return Value

Matching attribute

#### Discussion

Starting with CUPS 2.0, the attribute name can contain a hierarchical list of attribute and member names separated by slashes, for example "media-col/media-size".

### ippFindNextAttribute

Find the next named attribute in a request.

ipp_attribute_t *ippFindNextAttribute(ipp_t *ipp, const char *name, ipp_tag_t type);

#### Parameters

ipp | IPP message
name | Name of attribute
type | Type of attribute

#### Return Value

Matching attribute

#### Discussion

Starting with CUPS 2.0, the attribute name can contain a hierarchical list of attribute and member names separated by slashes, for example "media-col/media-size".

### CUPS 1.6/macOS 10.8 ippFirstAttribute

Return the first attribute in the message.

ipp_attribute_t *ippFirstAttribute(ipp_t *ipp);

#### Parameters

ipp | IPP message

#### Return Value

First attribute or `NULL` if none

### CUPS 1.6/macOS 10.8 ippGetBoolean

Get a boolean value for an attribute.

int ippGetBoolean(ipp_attribute_t *attr, int element);

#### Parameters

attr | IPP attribute
element | Value number (0-based)

#### Return Value

Boolean value or 0 on error

#### Discussion

The `element` parameter specifies which value to get from 0 to `ippGetCount(attr)` - 1.

### CUPS 1.6/macOS 10.8 ippGetCollection

Get a collection value for an attribute.

ipp_t *ippGetCollection(ipp_attribute_t *attr, int element);

#### Parameters

attr | IPP attribute
element | Value number (0-based)

#### Return Value

Collection value or `NULL` on error

#### Discussion

The `element` parameter specifies which value to get from 0 to `ippGetCount(attr)` - 1.

### CUPS 1.6/macOS 10.8 ippGetCount

Get the number of values in an attribute.

int ippGetCount(ipp_attribute_t *attr);

#### Parameters

attr | IPP attribute

#### Return Value

Number of values or 0 on error

### CUPS 1.6/macOS 10.8 ippGetDate

Get a dateTime value for an attribute.

const ipp_uchar_t *ippGetDate(ipp_attribute_t *attr, int element);

#### Parameters

attr | IPP attribute
element | Value number (0-based)

#### Return Value

dateTime value or `NULL`

#### Discussion

The `element` parameter specifies which value to get from 0 to `ippGetCount(attr)` - 1.

### CUPS 1.6/macOS 10.8 ippGetGroupTag

Get the group associated with an attribute.

ipp_tag_t ippGetGroupTag(ipp_attribute_t *attr);

#### Parameters

attr | IPP attribute

#### Return Value

Group tag or `IPP_TAG_ZERO` on error

### CUPS 1.6/macOS 10.8 ippGetInteger

Get the integer/enum value for an attribute.

int ippGetInteger(ipp_attribute_t *attr, int element);

#### Parameters

attr | IPP attribute
element | Value number (0-based)

#### Return Value

Value or 0 on error

#### Discussion

The `element` parameter specifies which value to get from 0 to `ippGetCount(attr)` - 1.

### CUPS 1.6/macOS 10.8 ippGetName

Get the attribute name.

const char *ippGetName(ipp_attribute_t *attr);

#### Parameters

attr | IPP attribute

#### Return Value

Attribute name or `NULL` for separators

### CUPS 1.7/macOS 10.9 ippGetOctetString

Get an octetString value from an IPP attribute.

void *ippGetOctetString(ipp_attribute_t *attr, int element, int *datalen);

#### Parameters

attr | IPP attribute
element | Value number (0-based)
datalen | Length of octetString data

#### Return Value

Pointer to octetString data

#### Discussion

The `element` parameter specifies which value to get from 0 to `ippGetCount(attr)` - 1.

### CUPS 1.6/macOS 10.8 ippGetOperation

Get the operation ID in an IPP message.

ipp_op_t ippGetOperation(ipp_t *ipp);

#### Parameters

ipp | IPP request message

#### Return Value

Operation ID or 0 on error

### CUPS 1.6/macOS 10.8 ippGetRange

Get a rangeOfInteger value from an attribute.

int ippGetRange(ipp_attribute_t *attr, int element, int *uppervalue);

#### Parameters

attr | IPP attribute
element | Value number (0-based)
uppervalue | Upper value of range

#### Return Value

Lower value of range or 0

#### Discussion

The `element` parameter specifies which value to get from 0 to `ippGetCount(attr)` - 1.

### CUPS 1.6/macOS 10.8 ippGetRequestId

Get the request ID from an IPP message.

int ippGetRequestId(ipp_t *ipp);

#### Parameters

ipp | IPP message

#### Return Value

Request ID or 0 on error

### CUPS 1.6/macOS 10.8 ippGetResolution

Get a resolution value for an attribute.

int ippGetResolution(ipp_attribute_t *attr, int element, int *yres, ipp_res_t *units);

#### Parameters

attr | IPP attribute
element | Value number (0-based)
yres | Vertical/feed resolution
units | Units for resolution

#### Return Value

Horizontal/cross feed resolution or 0

#### Discussion

The `element` parameter specifies which value to get from 0 to `ippGetCount(attr)` - 1.

### CUPS 1.6/macOS 10.8 ippGetState

Get the IPP message state.

ipp_state_t ippGetState(ipp_t *ipp);

#### Parameters

ipp | IPP message

#### Return Value

IPP message state value

### CUPS 1.6/macOS 10.8 ippGetStatusCode

Get the status code from an IPP response or event message.

ipp_status_t ippGetStatusCode(ipp_t *ipp);

#### Parameters

ipp | IPP response or event message

#### Return Value

Status code in IPP message

### ippGetString

const char *ippGetString(ipp_attribute_t *attr, int element, const char **language);

#### Parameters

attr | IPP attribute
element | Value number (0-based)
language | Language code (`NULL` for don't care)

#### Return Value

Get the string and optionally the language code for an attribute.

The `element` parameter specifies which value to get from 0 to `ippGetCount(attr)` - 1.

### CUPS 1.6/macOS 10.8 ippGetValueTag

Get the value tag for an attribute.

ipp_tag_t ippGetValueTag(ipp_attribute_t *attr);

#### Parameters

attr | IPP attribute

#### Return Value

Value tag or `IPP_TAG_ZERO` on error

### CUPS 1.6/macOS 10.8 ippGetVersion

Get the major and minor version number from an IPP message.

int ippGetVersion(ipp_t *ipp, int *minor);

#### Parameters

ipp | IPP message
minor | Minor version number or `NULL` for don't care

#### Return Value

Major version number or 0 on error

### ippLength

Compute the length of an IPP message.

size_t ippLength(ipp_t *ipp);

#### Parameters

ipp | IPP message

#### Return Value

Size of IPP message

### ippNew

Allocate a new IPP message.

ipp_t *ippNew(void);

#### Return Value

New IPP message

### CUPS 1.2/macOS 10.5 ippNewRequest

Allocate a new IPP request message.

ipp_t *ippNewRequest(ipp_op_t op);

#### Parameters

op | Operation code

#### Return Value

IPP request message

#### Discussion

The new request message is initialized with the "attributes-charset" and "attributes-natural-language" attributes added. The "attributes-natural-language" value is derived from the current locale.

### CUPS 1.7/macOS 10.9 ippNewResponse

Allocate a new IPP response message.

ipp_t *ippNewResponse(ipp_t *request);

#### Parameters

request | IPP request message

#### Return Value

IPP response message

#### Discussion

The new response message is initialized with the same "version-number", "request-id", "attributes-charset", and "attributes-natural-language" as the provided request message. If the "attributes-charset" or "attributes-natural-language" attributes are missing from the request, 'utf-8' and a value derived from the current locale are substituted, respectively.

### CUPS 1.6/macOS 10.8 ippNextAttribute

Return the next attribute in the message.

ipp_attribute_t *ippNextAttribute(ipp_t *ipp);

#### Parameters

ipp | IPP message

#### Return Value

Next attribute or `NULL` if none

### CUPS 1.2/macOS 10.5 ippOpString

Return a name for the given operation id.

const char *ippOpString(ipp_op_t op);

#### Parameters

op | Operation ID

#### Return Value

Name

### CUPS 1.2/macOS 10.5 ippOpValue

Return an operation id for the given name.

ipp_op_t ippOpValue(const char *name);

#### Parameters

name | Textual name

#### Return Value

Operation ID

### ippPort

Return the default IPP port number.

int ippPort(void);

#### Return Value

Port number

### ippRead

Read data for an IPP message from a HTTP connection.

ipp_state_t ippRead(http_t *http, ipp_t *ipp);

#### Parameters

http | HTTP connection
ipp | IPP data

#### Return Value

Current state

### CUPS 1.1.19/macOS 10.3 ippReadFile

Read data for an IPP message from a file.

ipp_state_t ippReadFile(int fd, ipp_t *ipp);

#### Parameters

fd | HTTP data
ipp | IPP data

#### Return Value

Current state

### CUPS 1.2/macOS 10.5 ippReadIO

Read data for an IPP message.

ipp_state_t ippReadIO(void *src, ipp_iocb_t cb, int blocking, ipp_t *parent, ipp_t *ipp);

#### Parameters

src | Data source
cb | Read callback function
blocking | Use blocking IO?
parent | Parent request, if any
ipp | IPP data

#### Return Value

Current state

### CUPS 1.6/macOS 10.8 ippSetBoolean

Set a boolean value in an attribute.

int ippSetBoolean(ipp_t *ipp, ipp_attribute_t **attr, int element, int boolvalue);

#### Parameters

ipp | IPP message
attr | IPP attribute
element | Value number (0-based)
boolvalue | Boolean value

#### Return Value

1 on success, 0 on failure

#### Discussion

The `ipp` parameter refers to an IPP message previously created using the `ippNew`, `ippNewRequest`, or `ippNewResponse` functions.
The `attr` parameter may be modified as a result of setting the value.
The `element` parameter specifies which value to set from 0 to `ippGetCount(attr)`.

### CUPS 1.6/macOS 10.8 ippSetCollection

Set a collection value in an attribute.

int ippSetCollection(ipp_t *ipp, ipp_attribute_t **attr, int element, ipp_t *colvalue);

#### Parameters

ipp | IPP message
attr | IPP attribute
element | Value number (0-based)
colvalue | Collection value

#### Return Value

1 on success, 0 on failure

#### Discussion

The `ipp` parameter refers to an IPP message previously created using the `ippNew`, `ippNewRequest`, or `ippNewResponse` functions.
The `attr` parameter may be modified as a result of setting the value.
The `element` parameter specifies which value to set from 0 to `ippGetCount(attr)`.

### CUPS 1.6/macOS 10.8 ippSetDate

Set a dateTime value in an attribute.

int ippSetDate(ipp_t *ipp, ipp_attribute_t **attr, int element, const ipp_uchar_t *datevalue);

#### Parameters

ipp | IPP message
attr | IPP attribute
element | Value number (0-based)
datevalue | dateTime value

#### Return Value

1 on success, 0 on failure

#### Discussion

The `ipp` parameter refers to an IPP message previously created using the `ippNew`, `ippNewRequest`, or `ippNewResponse` functions.
The `attr` parameter may be modified as a result of setting the value.
The `element` parameter specifies which value to set from 0 to `ippGetCount(attr)`.

### CUPS 1.6/macOS 10.8 ippSetGroupTag

Set the group tag of an attribute.

int ippSetGroupTag(ipp_t *ipp, ipp_attribute_t **attr, ipp_tag_t group_tag);

#### Parameters

ipp | IPP message
attr | Attribute
group_tag | Group tag

#### Return Value

1 on success, 0 on failure

#### Discussion

The `ipp` parameter refers to an IPP message previously created using the `ippNew`, `ippNewRequest`, or `ippNewResponse` functions.
The `attr` parameter may be modified as a result of setting the value.
The `group` parameter specifies the IPP attribute group tag: none (`IPP_TAG_ZERO`, for member attributes), document (`IPP_TAG_DOCUMENT`), event notification (`IPP_TAG_EVENT_NOTIFICATION`), operation (`IPP_TAG_OPERATION`), printer (`IPP_TAG_PRINTER`), subscription (`IPP_TAG_SUBSCRIPTION`), or unsupported (`IPP_TAG_UNSUPPORTED_GROUP`).

### CUPS 1.6/macOS 10.8 ippSetInteger

Set an integer or enum value in an attribute.

int ippSetInteger(ipp_t *ipp, ipp_attribute_t **attr, int element, int intvalue);

#### Parameters

ipp | IPP message
attr | IPP attribute
element | Value number (0-based)
intvalue | Integer/enum value

#### Return Value

1 on success, 0 on failure

#### Discussion

The `ipp` parameter refers to an IPP message previously created using the `ippNew`, `ippNewRequest`, or `ippNewResponse` functions.
The `attr` parameter may be modified as a result of setting the value.
The `element` parameter specifies which value to set from 0 to `ippGetCount(attr)`.

### CUPS 1.6/macOS 10.8 ippSetName

Set the name of an attribute.

int ippSetName(ipp_t *ipp, ipp_attribute_t **attr, const char *name);

#### Parameters

ipp | IPP message
attr | IPP attribute
name | Attribute name

#### Return Value

1 on success, 0 on failure

#### Discussion

The `ipp` parameter refers to an IPP message previously created using the `ippNew`, `ippNewRequest`, or `ippNewResponse` functions.
The `attr` parameter may be modified as a result of setting the value.

### CUPS 1.7/macOS 10.9 ippSetOctetString

Set an octetString value in an IPP attribute.

int ippSetOctetString(ipp_t *ipp, ipp_attribute_t **attr, int element, const void *data, int datalen);

#### Parameters

ipp | IPP message
attr | IPP attribute
element | Value number (0-based)
data | Pointer to octetString data
datalen | Length of octetString data

#### Return Value

1 on success, 0 on failure

#### Discussion

The `ipp` parameter refers to an IPP message previously created using the `ippNew`, `ippNewRequest`, or `ippNewResponse` functions.
The `attr` parameter may be modified as a result of setting the value.
The `element` parameter specifies which value to set from 0 to `ippGetCount(attr)`.

### CUPS 1.6/macOS 10.8 ippSetOperation

Set the operation ID in an IPP request message.

int ippSetOperation(ipp_t *ipp, ipp_op_t op);

#### Parameters

ipp | IPP request message
op | Operation ID

#### Return Value

1 on success, 0 on failure

#### Discussion

The `ipp` parameter refers to an IPP message previously created using the `ippNew`, `ippNewRequest`, or `ippNewResponse` functions.

### ippSetPort

Set the default port number.

void ippSetPort(int p);

#### Parameters

p | Port number to use

### CUPS 1.6/macOS 10.8 ippSetRange

Set a rangeOfInteger value in an attribute.

int ippSetRange(ipp_t *ipp, ipp_attribute_t **attr, int element, int lowervalue, int uppervalue);

#### Parameters

ipp | IPP message
attr | IPP attribute
element | Value number (0-based)
lowervalue | Lower bound for range
uppervalue | Upper bound for range

#### Return Value

1 on success, 0 on failure

#### Discussion

The `ipp` parameter refers to an IPP message previously created using the `ippNew`, `ippNewRequest`, or `ippNewResponse` functions.
The `attr` parameter may be modified as a result of setting the value.
The `element` parameter specifies which value to set from 0 to `ippGetCount(attr)`.

### CUPS 1.6/macOS 10.8 ippSetRequestId

Set the request ID in an IPP message.

int ippSetRequestId(ipp_t *ipp, int request_id);

#### Parameters

ipp | IPP message
request_id | Request ID

#### Return Value

1 on success, 0 on failure

#### Discussion

The `ipp` parameter refers to an IPP message previously created using the `ippNew`, `ippNewRequest`, or `ippNewResponse` functions.
The `request_id` parameter must be greater than 0.

### CUPS 1.6/macOS 10.8 ippSetResolution

Set a resolution value in an attribute.

int ippSetResolution(ipp_t *ipp, ipp_attribute_t **attr, int element, ipp_res_t unitsvalue, int xresvalue, int yresvalue);

#### Parameters

ipp | IPP message
attr | IPP attribute
element | Value number (0-based)
unitsvalue | Resolution units
xresvalue | Horizontal/cross feed resolution
yresvalue | Vertical/feed resolution

#### Return Value

1 on success, 0 on failure

#### Discussion

The `ipp` parameter refers to an IPP message previously created using the `ippNew`, `ippNewRequest`, or `ippNewResponse` functions.
The `attr` parameter may be modified as a result of setting the value.
The `element` parameter specifies which value to set from 0 to `ippGetCount(attr)`.

### CUPS 1.6/macOS 10.8 ippSetState

Set the current state of the IPP message.

int ippSetState(ipp_t *ipp, ipp_state_t state);

#### Parameters

ipp | IPP message
state | IPP state value

#### Return Value

1 on success, 0 on failure

### CUPS 1.6/macOS 10.8 ippSetStatusCode

Set the status code in an IPP response or event message.

int ippSetStatusCode(ipp_t *ipp, ipp_status_t status);

#### Parameters

ipp | IPP response or event message
status | Status code

#### Return Value

1 on success, 0 on failure

#### Discussion

The `ipp` parameter refers to an IPP message previously created using the `ippNew`, `ippNewRequest`, or `ippNewResponse` functions.

### CUPS 1.6/macOS 10.8 ippSetString

Set a string value in an attribute.

int ippSetString(ipp_t *ipp, ipp_attribute_t **attr, int element, const char *strvalue);

#### Parameters

ipp | IPP message
attr | IPP attribute
element | Value number (0-based)
strvalue | String value

#### Return Value

1 on success, 0 on failure

#### Discussion

The `ipp` parameter refers to an IPP message previously created using the `ippNew`, `ippNewRequest`, or `ippNewResponse` functions.
The `attr` parameter may be modified as a result of setting the value.
The `element` parameter specifies which value to set from 0 to `ippGetCount(attr)`.

### CUPS 1.7/macOS 10.9 ippSetStringf

Set a formatted string value of an attribute.

int ippSetStringf(ipp_t *ipp, ipp_attribute_t **attr, int element, const char *format, ...);

#### Parameters

ipp | IPP message
attr | IPP attribute
element | Value number (0-based)
format | Printf-style format string
... | Additional arguments as needed

#### Return Value

1 on success, 0 on failure

#### Discussion

The `ipp` parameter refers to an IPP message previously created using the `ippNew`, `ippNewRequest`, or `ippNewResponse` functions.
The `attr` parameter may be modified as a result of setting the value.
The `element` parameter specifies which value to set from 0 to `ippGetCount(attr)`.
The `format` parameter uses formatting characters compatible with the printf family of standard functions. Additional arguments follow it as needed. The formatted string is truncated as needed to the maximum length of the corresponding value type.

### CUPS 1.7/macOS 10.9 ippSetStringfv

Set a formatted string value of an attribute.

int ippSetStringfv(ipp_t *ipp, ipp_attribute_t **attr, int element, const char *format, va_list ap);

#### Parameters

ipp | IPP message
attr | IPP attribute
element | Value number (0-based)
format | Printf-style format string
ap | Pointer to additional arguments

#### Return Value

1 on success, 0 on failure

#### Discussion

The `ipp` parameter refers to an IPP message previously created using the `ippNew`, `ippNewRequest`, or `ippNewResponse` functions.
The `attr` parameter may be modified as a result of setting the value.
The `element` parameter specifies which value to set from 0 to `ippGetCount(attr)`.
The `format` parameter uses formatting characters compatible with the printf family of standard functions. Additional arguments follow it as needed. The formatted string is truncated as needed to the maximum length of the corresponding value type.

### CUPS 1.6/macOS 10.8 ippSetValueTag

Set the value tag of an attribute.

int ippSetValueTag(ipp_t *ipp, ipp_attribute_t **attr, ipp_tag_t value_tag);

#### Parameters

ipp | IPP message
attr | IPP attribute
value_tag | Value tag

#### Return Value

1 on success, 0 on failure

#### Discussion

The `ipp` parameter refers to an IPP message previously created using the `ippNew`, `ippNewRequest`, or `ippNewResponse` functions.
The `attr` parameter may be modified as a result of setting the value.
Integer (`IPP_TAG_INTEGER`) values can be promoted to rangeOfInteger (`IPP_TAG_RANGE`) values, the various string tags can be promoted to name (`IPP_TAG_NAME`) or nameWithLanguage (`IPP_TAG_NAMELANG`) values, text (`IPP_TAG_TEXT`) values can be promoted to textWithLanguage (`IPP_TAG_TEXTLANG`) values, and all values can be demoted to the various out-of-band value tags such as no-value (`IPP_TAG_NOVALUE`). All other changes will be rejected.
Promoting a string attribute to nameWithLanguage or textWithLanguage adds the language code in the "attributes-natural-language" attribute or, if not present, the language code for the current locale.

### CUPS 1.6/macOS 10.8 ippSetVersion

Set the version number in an IPP message.

int ippSetVersion(ipp_t *ipp, int major, int minor);

#### Parameters

ipp | IPP message
major | Major version number (major.minor)
minor | Minor version number (major.minor)

#### Return Value

1 on success, 0 on failure

#### Discussion

The `ipp` parameter refers to an IPP message previously created using the `ippNew`, `ippNewRequest`, or `ippNewResponse` functions.
The valid version numbers are currently 1.0, 1.1, 2.0, 2.1, and 2.2.

### CUPS 2.0/OS 10.10 ippStateString

Return the name corresponding to a state value.

const char *ippStateString(ipp_state_t state);

#### Parameters

state | State value

#### Return Value

State name

### CUPS 1.4/macOS 10.6 ippTagString

Return the tag name corresponding to a tag value.

const char *ippTagString(ipp_tag_t tag);

#### Parameters

tag | Tag value

#### Return Value

Tag name

#### Discussion

The returned names are defined in RFC 8011 and the IANA IPP Registry.

### CUPS 1.4/macOS 10.6 ippTagValue

Return the tag value corresponding to a tag name.

ipp_tag_t ippTagValue(const char *name);

#### Parameters

name | Tag name

#### Return Value

Tag value

#### Discussion

The tag names are defined in RFC 8011 and the IANA IPP Registry.

### ippTimeToDate

Convert from time in seconds to RFC 2579 format.

const ipp_uchar_t *ippTimeToDate(time_t t);

#### Parameters

t | Time in seconds

#### Return Value

RFC-2579 date/time data

### CUPS 1.7/macOS 10.9 ippValidateAttribute

Validate the contents of an attribute.

int ippValidateAttribute(ipp_attribute_t *attr);

#### Parameters

attr | Attribute

#### Return Value

1 if valid, 0 otherwise

#### Discussion

This function validates the contents of an attribute based on the name and value tag. 1 is returned if the attribute is valid, 0 otherwise. On failure, `cupsLastErrorString` is set to a human-readable message.

### CUPS 1.7/macOS 10.9 ippValidateAttributes

Validate all attributes in an IPP message.

int ippValidateAttributes(ipp_t *ipp);

#### Parameters

ipp | IPP message

#### Return Value

1 if valid, 0 otherwise

#### Discussion

This function validates the contents of the IPP message, including each attribute. Like `ippValidateAttribute`, `cupsLastErrorString` is set to a human-readable message on failure.

### ippWrite

Write data for an IPP message to a HTTP connection.

ipp_state_t ippWrite(http_t *http, ipp_t *ipp);

#### Parameters

http | HTTP connection
ipp | IPP data

#### Return Value

Current state

### CUPS 1.1.19/macOS 10.3 ippWriteFile

Write data for an IPP message to a file.

ipp_state_t ippWriteFile(int fd, ipp_t *ipp);

#### Parameters

fd | HTTP data
ipp | IPP data

#### Return Value

Current state

### CUPS 1.2/macOS 10.5 ippWriteIO

Write data for an IPP message.

ipp_state_t ippWriteIO(void *dst, ipp_iocb_t cb, int blocking, ipp_t *parent, ipp_t *ipp);

#### Parameters

dst | Destination
cb | Write callback function
blocking | Use blocking IO?
parent | Parent IPP message
ipp | IPP data

#### Return Value

Current state

## Data Types

### CUPS 1.5/macOS 10.7 cups_client_cert_cb_t

Client credentials callback

typedef int(*)(http_t *http, void *tls, cups_array_t *distinguished_names, void *user_data)cups_client_cert_cb_t;

### CUPS 1.6/macOS 10.8 cups_dest_cb_t

Destination enumeration callback

typedef int(*)(void *user_data, unsigned flags, cups_dest_t *dest)cups_dest_cb_t;

### cups_dest_t

Destination

typedef struct cups_dest_s cups_dest_t;

### CUPS 1.6/macOS 10.8 cups_dinfo_t

Destination capability and status information

typedef struct _cups_dinfo_s cups_dinfo_t;

### cups_job_t

Job

typedef struct cups_job_s cups_job_t;

### cups_option_t

Printer Options

typedef struct cups_option_s cups_option_t;

### CUPS 1.4/macOS 10.6 cups_password_cb2_t

New password callback

typedef const char *(*)(const char *prompt, http_t *http, const char *method, const char *resource, void *user_data)cups_password_cb2_t;

### cups_ptype_t

Printer type/capability bits

typedef unsigned cups_ptype_t;

### CUPS 1.5/macOS 10.7 cups_server_cert_cb_t

Server credentials callback

typedef int(*)(http_t *http, void *tls, cups_array_t *certs, void *user_data)cups_server_cert_cb_t;

### CUPS 1.6/macOS 10.8 cups_size_t

Media Size

typedef struct cups_size_s cups_size_t;

### CUPS 1.2/macOS 10.5 http_addr_t

Socket address union, which makes using IPv6 and other address types easier and more portable.

typedef union _http_addr_u / http_addr_t;

### http_encoding_t

HTTP transfer encoding values

typedef enum http_encoding_e http_encoding_t;

### http_encryption_t

HTTP encryption values

typedef enum http_encryption_e http_encryption_t;

### http_field_t

HTTP field names

typedef enum http_field_e http_field_t;

### http_keepalive_t

HTTP keep-alive values

typedef enum http_keepalive_e http_keepalive_t;

### http_state_t

HTTP state values; states are server-oriented...

typedef enum http_state_e http_state_t;

### http_t

HTTP connection type

typedef struct _http_s http_t;

### CUPS 1.5/macOS 10.7 http_timeout_cb_t

HTTP timeout callback

typedef int(*)(http_t *http, void *user_data)http_timeout_cb_t;

### CUPS 2.0/OS 10.10 http_trust_t

Level of trust for credentials

typedef enum http_trust_e http_trust_t;

### http_uri_coding_t

URI en/decode flags

typedef enum http_uri_coding_e http_uri_coding_t;

### CUPS 1.2 http_uri_status_t

URI separation status

typedef enum http_uri_status_e http_uri_status_t;

### ipp_attribute_t

IPP attribute

typedef struct _ipp_attribute_s ipp_attribute_t;

### CUPS 1.6/macOS 10.8 ipp_copycb_t

ippCopyAttributes callback function

typedef int(*)(void *context, ipp_t *dst, ipp_attribute_t *attr)ipp_copycb_t;

### CUPS 1.2/macOS 10.5 ipp_iocb_t

ippReadIO/ippWriteIO callback function

typedef ssize_t(*)(void *context, ipp_uchar_t *buffer, size_t bytes) ipp_iocb_t;

### ipp_orient_t

Orientation values

typedef enum ipp_orient_e ipp_orient_t;

### ipp_pstate_t

Printer state values

typedef enum ipp_pstate_e ipp_pstate_t;

### ipp_quality_t

Print quality values

typedef enum ipp_quality_e ipp_quality_t;

### ipp_res_t

Resolution units

typedef enum ipp_res_e ipp_res_t;

### ipp_rstate_t

resource-state values

typedef enum ipp_rstate_e ipp_rstate_t;

### ipp_sstate_t

system-state values

typedef enum ipp_sstate_e ipp_sstate_t;

### ipp_state_t

ipp_t state values

typedef enum ipp_state_e ipp_state_t;

### ipp_t

IPP request/response data

typedef struct _ipp_s ipp_t;

## Structures

### cups_dest_s

Destination

struct cups_dest_s {
char *name, *instance;
int is_default;
int num_options;
cups_option_t *options;
};

#### Members

instance | Local instance name or NULL
is_default | Is this printer the default?
num_options | Number of options
options | Options

### cups_job_s

Job

struct cups_job_s {
time_t completed_time;
time_t creation_time;
char *dest;
char *format;
int id;
int priority;
time_t processing_time;
int size;
ipp_jstate_t state;
char *title;
char *user;
};

#### Members

completed_time | Time the job was completed
creation_time | Time the job was created
dest | Printer or class name
format | Document format
id | The job ID
priority | Priority (1-100)
processing_time | Time the job was processed
size | Size in kilobytes
state | Job state
title | Title/job name
user | User that submitted the job

### cups_option_s

Printer Options

struct cups_option_s {
char *name;
char *value;
};

#### Members

name | Name of option
value | Value of option

### CUPS 1.6/macOS 10.8 cups_size_s

Media Size

struct cups_size_s {
char media[128];
int width, length, bottom, left, right, top;
};

#### Members

media[128] | Media name to use
top | Top margin in hundredths of millimeters

## Constants

### cups_ptype_e

Printer type/capability bit constants

#### Constants

CUPS_PRINTER_AUTHENTICATED CUPS 1.2/macOS 10.5 | Printer requires authentication
CUPS_PRINTER_BIND | Can bind output
CUPS_PRINTER_BW | Can do B&W printing
CUPS_PRINTER_CLASS | Printer class
CUPS_PRINTER_COLLATE | Can quickly collate copies
CUPS_PRINTER_COLOR | Can do color printing
CUPS_PRINTER_COMMANDS CUPS 1.2/macOS 10.5 | Printer supports maintenance commands
CUPS_PRINTER_COPIES | Can do copies in hardware
CUPS_PRINTER_COVER | Can cover output
CUPS_PRINTER_DEFAULT | Default printer on network
CUPS_PRINTER_DISCOVERED CUPS 1.2/macOS 10.5 | Printer was discovered
CUPS_PRINTER_DUPLEX | Can do two-sided printing
CUPS_PRINTER_FAX | Fax queue
CUPS_PRINTER_LARGE | Can print on D/E/A1/A0-size media
CUPS_PRINTER_LOCAL | Local printer or class
CUPS_PRINTER_MEDIUM | Can print on Tabloid/B/C/A3/A2-size media
CUPS_PRINTER_NOT_SHARED CUPS 1.2/macOS 10.5 | Printer is not shared
CUPS_PRINTER_PUNCH | Can punch output
CUPS_PRINTER_REJECTING | Printer is rejecting jobs
CUPS_PRINTER_REMOTE | Remote printer or class
CUPS_PRINTER_SMALL | Can print on Letter/Legal/A4-size media
CUPS_PRINTER_SORT | Can sort output
CUPS_PRINTER_STAPLE | Can staple output
CUPS_PRINTER_VARIABLE | Can print on rolls and custom-size media

### http_encoding_e

HTTP transfer encoding values

#### Constants

HTTP_ENCODING_CHUNKED | Data is chunked
HTTP_ENCODING_FIELDS | Sending HTTP fields
HTTP_ENCODING_LENGTH | Data is sent with Content-Length

### http_encryption_e

HTTP encryption values

#### Constants

HTTP_ENCRYPTION_ALWAYS | Always encrypt (SSL)
HTTP_ENCRYPTION_IF_REQUESTED | Encrypt if requested (TLS upgrade)
HTTP_ENCRYPTION_NEVER | Never encrypt
HTTP_ENCRYPTION_REQUIRED | Encryption is required (TLS upgrade)

### http_field_e

HTTP field names

#### Constants

HTTP_FIELD_ACCEPT_ENCODING CUPS 1.7/macOS 10.9 | Accepting-Encoding field
HTTP_FIELD_ACCEPT_LANGUAGE | Accept-Language field
HTTP_FIELD_ACCEPT_RANGES | Accept-Ranges field
HTTP_FIELD_ALLOW CUPS 1.7/macOS 10.9 | Allow field
HTTP_FIELD_AUTHORIZATION | Authorization field
HTTP_FIELD_CONNECTION | Connection field
HTTP_FIELD_CONTENT_ENCODING | Content-Encoding field
HTTP_FIELD_CONTENT_LANGUAGE | Content-Language field
HTTP_FIELD_CONTENT_LENGTH | Content-Length field
HTTP_FIELD_CONTENT_LOCATION | Content-Location field
HTTP_FIELD_CONTENT_MD5 | Content-MD5 field
HTTP_FIELD_CONTENT_RANGE | Content-Range field
HTTP_FIELD_CONTENT_TYPE | Content-Type field
HTTP_FIELD_CONTENT_VERSION | Content-Version field
HTTP_FIELD_DATE | Date field
HTTP_FIELD_HOST | Host field
HTTP_FIELD_IF_MODIFIED_SINCE | If-Modified-Since field
HTTP_FIELD_IF_UNMODIFIED_SINCE | If-Unmodified-Since field
HTTP_FIELD_KEEP_ALIVE | Keep-Alive field
HTTP_FIELD_LAST_MODIFIED | Last-Modified field
HTTP_FIELD_LINK | Link field
HTTP_FIELD_LOCATION | Location field
HTTP_FIELD_MAX | Maximum field index
HTTP_FIELD_RANGE | Range field
HTTP_FIELD_REFERER | Referer field
HTTP_FIELD_RETRY_AFTER | Retry-After field
HTTP_FIELD_SERVER CUPS 1.7/macOS 10.9 | Server field
HTTP_FIELD_TRANSFER_ENCODING | Transfer-Encoding field
HTTP_FIELD_UNKNOWN | Unknown field
HTTP_FIELD_UPGRADE | Upgrade field
HTTP_FIELD_USER_AGENT | User-Agent field
HTTP_FIELD_WWW_AUTHENTICATE | WWW-Authenticate field

### http_keepalive_e

HTTP keep-alive values

#### Constants

HTTP_KEEPALIVE_OFF | No keep alive support
HTTP_KEEPALIVE_ON | Use keep alive

### http_state_e

HTTP state values; states are server-oriented...

#### Constants

HTTP_STATE_CONNECT | CONNECT command, waiting for blank line
HTTP_STATE_DELETE | DELETE command, waiting for blank line
HTTP_STATE_ERROR | Error on socket
HTTP_STATE_GET | GET command, waiting for blank line
HTTP_STATE_GET_SEND | GET command, sending data
HTTP_STATE_HEAD | HEAD command, waiting for blank line
HTTP_STATE_OPTIONS | OPTIONS command, waiting for blank line
HTTP_STATE_POST | POST command, waiting for blank line
HTTP_STATE_POST_RECV | POST command, receiving data
HTTP_STATE_POST_SEND | POST command, sending data
HTTP_STATE_PUT | PUT command, waiting for blank line
HTTP_STATE_PUT_RECV | PUT command, receiving data
HTTP_STATE_STATUS | Command complete, sending status
HTTP_STATE_TRACE | TRACE command, waiting for blank line
HTTP_STATE_UNKNOWN_METHOD CUPS 1.7/macOS 10.9 | Unknown request method, waiting for blank line
HTTP_STATE_UNKNOWN_VERSION CUPS 1.7/macOS 10.9 | Unknown request method, waiting for blank line
HTTP_STATE_WAITING | Waiting for command

### http_status_e

HTTP status codes

#### Constants

HTTP_STATUS_ACCEPTED | DELETE command was successful
HTTP_STATUS_BAD_GATEWAY | Bad gateway
HTTP_STATUS_BAD_REQUEST | Bad request
HTTP_STATUS_CONFLICT | Request is self-conflicting
HTTP_STATUS_CONTINUE | Everything OK, keep going...
HTTP_STATUS_CREATED | PUT command was successful
HTTP_STATUS_CUPS_AUTHORIZATION_CANCELED CUPS 1.4 | User canceled authorization
HTTP_STATUS_CUPS_PKI_ERROR CUPS 1.5/macOS 10.7 | Error negotiating a secure connection
HTTP_STATUS_ERROR | An error response from httpXxxx()
HTTP_STATUS_EXPECTATION_FAILED | The expectation given in an Expect header field was not met
HTTP_STATUS_FORBIDDEN | Forbidden to access this URI
HTTP_STATUS_FOUND | Document was found at a different URI
HTTP_STATUS_GATEWAY_TIMEOUT | Gateway connection timed out
HTTP_STATUS_GONE | Server has gone away
HTTP_STATUS_LENGTH_REQUIRED | A content length or encoding is required
HTTP_STATUS_METHOD_NOT_ALLOWED | Method is not allowed
HTTP_STATUS_MOVED_PERMANENTLY | Document has moved permanently
HTTP_STATUS_MULTIPLE_CHOICES | Multiple files match request
HTTP_STATUS_NONE CUPS 1.7/macOS 10.9 | No Expect value
HTTP_STATUS_NOT_ACCEPTABLE | Not Acceptable
HTTP_STATUS_NOT_AUTHORITATIVE | Information isn't authoritative
HTTP_STATUS_NOT_FOUND | URI was not found
HTTP_STATUS_NOT_IMPLEMENTED | Feature not implemented
HTTP_STATUS_NOT_MODIFIED | File not modified
HTTP_STATUS_NOT_SUPPORTED | HTTP version not supported
HTTP_STATUS_NO_CONTENT | Successful command, no new data
HTTP_STATUS_OK | OPTIONS/GET/HEAD/POST/TRACE command was successful
HTTP_STATUS_PARTIAL_CONTENT | Only a partial file was received/sent
HTTP_STATUS_PAYMENT_REQUIRED | Payment required
HTTP_STATUS_PRECONDITION | Precondition failed
HTTP_STATUS_PROXY_AUTHENTICATION | Proxy Authentication is Required
HTTP_STATUS_REQUESTED_RANGE | The requested range is not satisfiable
HTTP_STATUS_REQUEST_TIMEOUT | Request timed out
HTTP_STATUS_REQUEST_TOO_LARGE | Request entity too large
HTTP_STATUS_RESET_CONTENT | Content was reset/recreated
HTTP_STATUS_SEE_OTHER | See this other link
HTTP_STATUS_SERVER_ERROR | Internal server error
HTTP_STATUS_SERVICE_UNAVAILABLE | Service is unavailable
HTTP_STATUS_SWITCHING_PROTOCOLS | HTTP upgrade to TLS/SSL
HTTP_STATUS_TEMPORARY_REDIRECT | Temporary redirection
HTTP_STATUS_UNAUTHORIZED | Unauthorized to access host
HTTP_STATUS_UNSUPPORTED_MEDIATYPE | The requested media type is unsupported
HTTP_STATUS_UPGRADE_REQUIRED | Upgrade to SSL/TLS required
HTTP_STATUS_URI_TOO_LONG | URI too long
HTTP_STATUS_USE_PROXY | Must use a proxy to access this URI

### CUPS 2.0/OS 10.10 http_trust_e

Level of trust for credentials

#### Constants

HTTP_TRUST_CHANGED | Credentials have changed
HTTP_TRUST_EXPIRED | Credentials are expired
HTTP_TRUST_INVALID | Credentials are invalid
HTTP_TRUST_OK | Credentials are OK/trusted
HTTP_TRUST_RENEWED | Credentials have been renewed
HTTP_TRUST_UNKNOWN | Credentials are unknown/new

### http_uri_coding_e

URI en/decode flags

#### Constants

HTTP_URI_CODING_ALL | En/decode everything
HTTP_URI_CODING_HOSTNAME | En/decode the hostname portion
HTTP_URI_CODING_MOST | En/decode all but the query
HTTP_URI_CODING_NONE | Don't en/decode anything
HTTP_URI_CODING_QUERY | En/decode the query portion
HTTP_URI_CODING_RESOURCE | En/decode the resource portion
HTTP_URI_CODING_RFC6874 | Use RFC 6874 address format
HTTP_URI_CODING_USERNAME | En/decode the username portion

### CUPS 1.2 http_uri_status_e

URI separation status

#### Constants

HTTP_URI_STATUS_BAD_ARGUMENTS | Bad arguments to function (error)
HTTP_URI_STATUS_BAD_HOSTNAME | Bad hostname in URI (error)
HTTP_URI_STATUS_BAD_PORT | Bad port number in URI (error)
HTTP_URI_STATUS_BAD_RESOURCE | Bad resource in URI (error)
HTTP_URI_STATUS_BAD_SCHEME | Bad scheme in URI (error)
HTTP_URI_STATUS_BAD_URI | Bad/empty URI (error)
HTTP_URI_STATUS_BAD_USERNAME | Bad username in URI (error)
HTTP_URI_STATUS_MISSING_RESOURCE | Missing resource in URI (warning)
HTTP_URI_STATUS_MISSING_SCHEME | Missing scheme in URI (warning)
HTTP_URI_STATUS_OK | URI decoded OK
HTTP_URI_STATUS_OVERFLOW | URI buffer for httpAssembleURI is too small
HTTP_URI_STATUS_UNKNOWN_SCHEME | Unknown scheme in URI (warning)

### ipp_finishings_e

Finishings values

#### Constants

IPP_FINISHINGS_BALE | Bale (any type)
IPP_FINISHINGS_BIND | Bind
IPP_FINISHINGS_BIND_BOTTOM | Bind on bottom
IPP_FINISHINGS_BIND_LEFT | Bind on left
IPP_FINISHINGS_BIND_RIGHT | Bind on right
IPP_FINISHINGS_BIND_TOP | Bind on top
IPP_FINISHINGS_BOOKLET_MAKER | Fold to make booklet
IPP_FINISHINGS_COAT | Apply protective liquid or powder coating
IPP_FINISHINGS_COVER | Add cover
IPP_FINISHINGS_EDGE_STITCH | Stitch along any side
IPP_FINISHINGS_EDGE_STITCH_BOTTOM | Stitch along bottom edge
IPP_FINISHINGS_EDGE_STITCH_LEFT | Stitch along left side
IPP_FINISHINGS_EDGE_STITCH_RIGHT | Stitch along right side
IPP_FINISHINGS_EDGE_STITCH_TOP | Stitch along top edge
IPP_FINISHINGS_FOLD | Fold (any type)
IPP_FINISHINGS_FOLD_ACCORDIAN | Accordian-fold the paper vertically into four sections
IPP_FINISHINGS_FOLD_DOUBLE_GATE | Fold the top and bottom quarters of the paper towards the midline, then fold in half vertically
IPP_FINISHINGS_FOLD_ENGINEERING_Z | Fold the paper vertically into two small sections and one larger, forming an elongated Z
IPP_FINISHINGS_FOLD_GATE | Fold the top and bottom quarters of the paper towards the midline
IPP_FINISHINGS_FOLD_HALF | Fold the paper in half vertically
IPP_FINISHINGS_FOLD_HALF_Z | Fold the paper in half horizontally, then Z-fold the paper vertically
IPP_FINISHINGS_FOLD_LEFT_GATE | Fold the top quarter of the paper towards the midline
IPP_FINISHINGS_FOLD_LETTER | Fold the paper into three sections vertically; sometimes also known as a C fold
IPP_FINISHINGS_FOLD_PARALLEL | Fold the paper in half vertically two times, yielding four sections
IPP_FINISHINGS_FOLD_POSTER | Fold the paper in half horizontally and vertically; sometimes also called a cross fold
IPP_FINISHINGS_FOLD_RIGHT_GATE | Fold the bottom quarter of the paper towards the midline
IPP_FINISHINGS_FOLD_Z | Fold the paper vertically into three sections, forming a Z
IPP_FINISHINGS_JOG_OFFSET | Offset for binding (any type)
IPP_FINISHINGS_LAMINATE | Apply protective (solid) material
IPP_FINISHINGS_NONE | No finishing
IPP_FINISHINGS_PUNCH | Punch (any location/count)
IPP_FINISHINGS_PUNCH_BOTTOM_LEFT | Punch 1 hole bottom left
IPP_FINISHINGS_PUNCH_BOTTOM_RIGHT | Punch 1 hole bottom right
IPP_FINISHINGS_PUNCH_DUAL_BOTTOM | Punch 2 holes bottom edge
IPP_FINISHINGS_PUNCH_DUAL_LEFT | Punch 2 holes left side
IPP_FINISHINGS_PUNCH_DUAL_RIGHT | Punch 2 holes right side
IPP_FINISHINGS_PUNCH_DUAL_TOP | Punch 2 holes top edge
IPP_FINISHINGS_PUNCH_MULTIPLE_BOTTOM | Pucnh multiple holes bottom edge
IPP_FINISHINGS_PUNCH_MULTIPLE_LEFT | Pucnh multiple holes left side
IPP_FINISHINGS_PUNCH_MULTIPLE_RIGHT | Pucnh multiple holes right side
IPP_FINISHINGS_PUNCH_MULTIPLE_TOP | Pucnh multiple holes top edge
IPP_FINISHINGS_PUNCH_QUAD_BOTTOM | Punch 4 holes bottom edge
IPP_FINISHINGS_PUNCH_QUAD_LEFT | Punch 4 holes left side
IPP_FINISHINGS_PUNCH_QUAD_RIGHT | Punch 4 holes right side
IPP_FINISHINGS_PUNCH_QUAD_TOP | Punch 4 holes top edge
IPP_FINISHINGS_PUNCH_TOP_LEFT | Punch 1 hole top left
IPP_FINISHINGS_PUNCH_TOP_RIGHT | Punch 1 hole top right
IPP_FINISHINGS_PUNCH_TRIPLE_BOTTOM | Punch 3 holes bottom edge
IPP_FINISHINGS_PUNCH_TRIPLE_LEFT | Punch 3 holes left side
IPP_FINISHINGS_PUNCH_TRIPLE_RIGHT | Punch 3 holes right side
IPP_FINISHINGS_PUNCH_TRIPLE_TOP | Punch 3 holes top edge
IPP_FINISHINGS_SADDLE_STITCH | Staple interior
IPP_FINISHINGS_STAPLE | Staple (any location/method)
IPP_FINISHINGS_STAPLE_BOTTOM_LEFT | Staple bottom left corner
IPP_FINISHINGS_STAPLE_BOTTOM_RIGHT | Staple bottom right corner
IPP_FINISHINGS_STAPLE_DUAL_BOTTOM | Two staples on bottom
IPP_FINISHINGS_STAPLE_DUAL_LEFT | Two staples on left
IPP_FINISHINGS_STAPLE_DUAL_RIGHT | Two staples on right
IPP_FINISHINGS_STAPLE_DUAL_TOP | Two staples on top
IPP_FINISHINGS_STAPLE_TOP_LEFT | Staple top left corner
IPP_FINISHINGS_STAPLE_TOP_RIGHT | Staple top right corner
IPP_FINISHINGS_STAPLE_TRIPLE_BOTTOM | Three staples on bottom
IPP_FINISHINGS_STAPLE_TRIPLE_LEFT | Three staples on left
IPP_FINISHINGS_STAPLE_TRIPLE_RIGHT | Three staples on right
IPP_FINISHINGS_STAPLE_TRIPLE_TOP | Three staples on top
IPP_FINISHINGS_TRIM | Trim (any type)
IPP_FINISHINGS_TRIM_AFTER_COPIES | Trim output after each copy
IPP_FINISHINGS_TRIM_AFTER_DOCUMENTS | Trim output after each document
IPP_FINISHINGS_TRIM_AFTER_JOB | Trim output after job
IPP_FINISHINGS_TRIM_AFTER_PAGES | Trim output after each page

### ipp_jstate_e

Job states

#### Constants

IPP_JSTATE_ABORTED | Job has aborted due to error
IPP_JSTATE_CANCELED | Job has been canceled
IPP_JSTATE_COMPLETED | Job has completed successfully
IPP_JSTATE_HELD | Job is held for printing
IPP_JSTATE_PENDING | Job is waiting to be printed
IPP_JSTATE_PROCESSING | Job is currently printing
IPP_JSTATE_STOPPED | Job has been stopped

### ipp_op_e

IPP operations

#### Constants

IPP_OP_ALLOCATE_PRINTER_RESOURCES | Allocate-Printer-Resources: Use resources for a printer.
IPP_OP_CANCEL_CURRENT_JOB | Cancel-Current-Job: Cancel the current job
IPP_OP_CANCEL_JOB | Cancel-Job: Cancel a job
IPP_OP_CANCEL_JOBS | Cancel-Jobs: Cancel all jobs (administrative)
IPP_OP_CANCEL_MY_JOBS | Cancel-My-Jobs: Cancel a user's jobs
IPP_OP_CANCEL_RESOURCE | Cancel-Resource: Uninstall a resource.
IPP_OP_CANCEL_SUBSCRIPTION CUPS 1.2/macOS 10.5 | Cancel-Subscription: Cancel a subscription
IPP_OP_CLOSE_JOB | Close-Job: Close a job and start printing
IPP_OP_CREATE_JOB | Create-Job: Create an empty print job
IPP_OP_CREATE_JOB_SUBSCRIPTIONS CUPS 1.2/macOS 10.5 | Create-Job-Subscriptions: Create one of more job subscriptions
IPP_OP_CREATE_PRINTER | Create-Printer: Create a new service.
IPP_OP_CREATE_PRINTER_SUBSCRIPTIONS CUPS 1.2/macOS 10.5 | Create-Printer-Subscriptions: Create one or more printer subscriptions
IPP_OP_CREATE_RESOURCE | Create-Resource: Create a new (empty) resource.
IPP_OP_CREATE_RESOURCE_SUBSCRIPTIONS | Create-Resource-Subscriptions: Create event subscriptions for a resource.
IPP_OP_CREATE_SYSTEM_SUBSCRIPTIONS | Create-System-Subscriptions: Create event subscriptions for a system.
IPP_OP_CUPS_ADD_MODIFY_CLASS | CUPS-Add-Modify-Class: Add or modify a class
IPP_OP_CUPS_ADD_MODIFY_PRINTER | CUPS-Add-Modify-Printer: Add or modify a printer
IPP_OP_CUPS_AUTHENTICATE_JOB CUPS 1.2/macOS 10.5 | CUPS-Authenticate-Job: Authenticate a job
IPP_OP_CUPS_CREATE_LOCAL_PRINTER CUPS 2.2 | CUPS-Create-Local-Printer: Create a local (temporary) printer
IPP_OP_CUPS_DELETE_CLASS | CUPS-Delete-Class: Delete a class
IPP_OP_CUPS_DELETE_PRINTER | CUPS-Delete-Printer: Delete a printer
IPP_OP_CUPS_GET_DEFAULT | CUPS-Get-Default: Get the default printer
IPP_OP_CUPS_GET_DEVICES DEPRECATED | CUPS-Get-Devices: Get a list of supported devices
IPP_OP_CUPS_GET_DOCUMENT CUPS 1.4/macOS 10.6 | CUPS-Get-Document: Get a document file
IPP_OP_CUPS_GET_PPD DEPRECATED | CUPS-Get-PPD: Get a PPD file
IPP_OP_CUPS_GET_PPDS DEPRECATED | CUPS-Get-PPDs: Get a list of supported drivers
IPP_OP_CUPS_GET_PRINTERS | CUPS-Get-Printers: Get a list of printers and/or classes
IPP_OP_CUPS_INVALID | Invalid operation name for `ippOpValue`
IPP_OP_CUPS_MOVE_JOB | CUPS-Move-Job: Move a job to a different printer
IPP_OP_CUPS_SET_DEFAULT | CUPS-Set-Default: Set the default printer
IPP_OP_DEALLOCATE_PRINTER_RESOURCES | Deallocate-Printer-Resources: Stop using resources for a printer.
IPP_OP_DELETE_PRINTER | Delete-Printer: Delete an existing service.
IPP_OP_DISABLE_ALL_PRINTERS | Disable-All-Printers: Stop accepting new jobs on all services.
IPP_OP_DISABLE_PRINTER | Disable-Printer: Reject new jobs for a printer
IPP_OP_ENABLE_ALL_PRINTERS | Enable-All-Printers: Start accepting new jobs on all services.
IPP_OP_ENABLE_PRINTER | Enable-Printer: Accept new jobs for a printer
IPP_OP_GET_JOBS | Get-Jobs: Get a list of jobs
IPP_OP_GET_JOB_ATTRIBUTES | Get-Job-Attribute: Get information about a job
IPP_OP_GET_NOTIFICATIONS CUPS 1.2/macOS 10.5 | Get-Notifications: Get notification events
IPP_OP_GET_PRINTERS | Get-Printers: Get a list of services.
IPP_OP_GET_PRINTER_ATTRIBUTES | Get-Printer-Attributes: Get information about a printer
IPP_OP_GET_PRINTER_SUPPORTED_VALUES | Get-Printer-Supported-Values: Get supported values
IPP_OP_GET_SUBSCRIPTIONS CUPS 1.2/macOS 10.5 | Get-Subscriptions: Get list of subscriptions
IPP_OP_GET_SUBSCRIPTION_ATTRIBUTES CUPS 1.2/macOS 10.5 | Get-Subscription-Attributes: Get subscription information
IPP_OP_GET_SYSTEM_ATTRIBUTES | Get-System-Attributes: Get system object attributes.
IPP_OP_GET_SYSTEM_SUPPORTED_VALUES | Get-System-Supported-Values: Get supported values for system object attributes.
IPP_OP_HOLD_JOB | Hold-Job: Hold a job for printing
IPP_OP_HOLD_NEW_JOBS | Hold-New-Jobs: Hold new jobs
IPP_OP_IDENTIFY_PRINTER | Identify-Printer: Make the printer beep, flash, or display a message for identification
IPP_OP_INSTALL_RESOURCE | Install-Resource: Install a resource.
IPP_OP_PAUSE_ALL_PRINTERS | Pause-All-Printers: Stop all services immediately.
IPP_OP_PAUSE_ALL_PRINTERS_AFTER_CURRENT_JOB | Pause-All-Printers-After-Current-Job: Stop all services after processing the current jobs.
IPP_OP_PAUSE_PRINTER | Pause-Printer: Stop a printer
IPP_OP_PAUSE_PRINTER_AFTER_CURRENT_JOB | Pause-Printer-After-Current-Job: Stop printer after the current job
IPP_OP_PRINT_JOB | Print-Job: Print a single file
IPP_OP_PROMOTE_JOB | Promote-Job: Promote a job to print sooner
IPP_OP_REGISTER_OUTPUT_DEVICE | Register-Output-Device: Register a remote service.
IPP_OP_RELEASE_HELD_NEW_JOBS | Release-Held-New-Jobs: Release new jobs that were previously held
IPP_OP_RELEASE_JOB | Release-Job: Release a job for printing
IPP_OP_RENEW_SUBSCRIPTION CUPS 1.2/macOS 10.5 | Renew-Subscription: Renew a printer subscription
IPP_OP_RESTART_JOB DEPRECATED | Restart-Job: Reprint a job
IPP_OP_RESTART_SYSTEM | Restart-System: Restart all services.
IPP_OP_RESUME_ALL_PRINTERS | Resume-All-Printers: Start job processing on all services.
IPP_OP_RESUME_JOB | Resume-Job: Resume the current job
IPP_OP_RESUME_PRINTER | Resume-Printer: Start a printer
IPP_OP_SCHEDULE_JOB_AFTER | Schedule-Job-After: Schedule a job to print after another
IPP_OP_SEND_DOCUMENT | Send-Document: Add a file to a job
IPP_OP_SEND_RESOURCE_DATA | Send-Resource-Data: Upload the data for a resource.
IPP_OP_SET_JOB_ATTRIBUTES | Set-Job-Attributes: Set job values
IPP_OP_SET_PRINTER_ATTRIBUTES | Set-Printer-Attributes: Set printer values
IPP_OP_SET_RESOURCE_ATTRIBUTES | Set-Resource-Attributes: Set resource object attributes.
IPP_OP_SET_SYSTEM_ATTRIBUTES | Set-System-Attributes: Set system object attributes.
IPP_OP_SHUTDOWN_ALL_PRINTERS | Shutdown-All-Printers: Shutdown all services.
IPP_OP_SHUTDOWN_ONE_PRINTER | Shutdown-One-Printer: Shutdown a service.
IPP_OP_STARTUP_ALL_PRINTERS | Startup-All-Printers: Startup all services.
IPP_OP_STARTUP_ONE_PRINTER | Startup-One-Printer: Start a service.
IPP_OP_SUSPEND_CURRENT_JOB | Suspend-Current-Job: Suspend the current job
IPP_OP_VALIDATE_JOB | Validate-Job: Validate job values prior to submission

### ipp_orient_e

Orientation values

#### Constants

IPP_ORIENT_LANDSCAPE | 90 degrees counter-clockwise
IPP_ORIENT_NONE | No rotation
IPP_ORIENT_PORTRAIT | No rotation
IPP_ORIENT_REVERSE_LANDSCAPE | 90 degrees clockwise
IPP_ORIENT_REVERSE_PORTRAIT | 180 degrees

### ipp_pstate_e

Printer state values

#### Constants

IPP_PSTATE_IDLE | Printer is idle
IPP_PSTATE_PROCESSING | Printer is working
IPP_PSTATE_STOPPED | Printer is stopped

### ipp_quality_e

Print quality values

#### Constants

IPP_QUALITY_DRAFT | Draft quality
IPP_QUALITY_HIGH | High quality
IPP_QUALITY_NORMAL | Normal quality

### ipp_res_e

Resolution units

#### Constants

IPP_RES_PER_CM | Pixels per centimeter
IPP_RES_PER_INCH | Pixels per inch

### ipp_rstate_e

resource-state values

#### Constants

IPP_RSTATE_ABORTED | Resource has been aborted and is pending deletion.
IPP_RSTATE_AVAILABLE | Resource is available for installation.
IPP_RSTATE_CANCELED | Resource has been canceled and is pending deletion.
IPP_RSTATE_INSTALLED | Resource is installed.
IPP_RSTATE_PENDING | Resource is created but has no data yet.

### ipp_sstate_e

system-state values

#### Constants

IPP_SSTATE_IDLE | At least one printer is idle and none are processing a job.
IPP_SSTATE_PROCESSING | At least one printer is processing a job.
IPP_SSTATE_STOPPED | All printers are stopped.

### ipp_state_e

ipp_t state values

#### Constants

IPP_STATE_ATTRIBUTE | One or more attributes need to be sent/received
IPP_STATE_DATA | IPP request data needs to be sent/received
IPP_STATE_ERROR | An error occurred
IPP_STATE_HEADER | The request header needs to be sent/received
IPP_STATE_IDLE | Nothing is happening/request completed

### ipp_status_e

IPP status code values

#### Constants

IPP_STATUS_CUPS_INVALID | Invalid status name for `ippErrorValue`
IPP_STATUS_ERROR_ACCOUNT_AUTHORIZATION_FAILED | client-error-account-authorization-failed
IPP_STATUS_ERROR_ACCOUNT_CLOSED | client-error-account-closed
IPP_STATUS_ERROR_ACCOUNT_INFO_NEEDED | client-error-account-info-needed
IPP_STATUS_ERROR_ACCOUNT_LIMIT_REACHED | client-error-account-limit-reached
IPP_STATUS_ERROR_ATTRIBUTES_NOT_SETTABLE | client-error-attributes-not-settable
IPP_STATUS_ERROR_ATTRIBUTES_OR_VALUES | client-error-attributes-or-values-not-supported
IPP_STATUS_ERROR_BAD_REQUEST | client-error-bad-request
IPP_STATUS_ERROR_BUSY | server-error-busy
IPP_STATUS_ERROR_CHARSET | client-error-charset-not-supported
IPP_STATUS_ERROR_COMPRESSION_ERROR | client-error-compression-error
IPP_STATUS_ERROR_COMPRESSION_NOT_SUPPORTED | client-error-compression-not-supported
IPP_STATUS_ERROR_CONFLICTING | client-error-conflicting-attributes
IPP_STATUS_ERROR_CUPS_ACCOUNT_AUTHORIZATION_FAILED DEPRECATED | cups-error-account-authorization-failed
IPP_STATUS_ERROR_CUPS_ACCOUNT_CLOSED | cups-error-account-closed @deprecate@
IPP_STATUS_ERROR_CUPS_ACCOUNT_INFO_NEEDED DEPRECATED | cups-error-account-info-needed
IPP_STATUS_ERROR_CUPS_ACCOUNT_LIMIT_REACHED DEPRECATED | cups-error-account-limit-reached
IPP_STATUS_ERROR_CUPS_AUTHENTICATION_CANCELED CUPS 1.5/macOS 10.7 | cups-authentication-canceled - Authentication canceled by user
IPP_STATUS_ERROR_CUPS_PKI CUPS 1.5/macOS 10.7 | cups-pki-error - Error negotiating a secure connection
IPP_STATUS_ERROR_CUPS_UPGRADE_REQUIRED CUPS 1.5/macOS 10.7 | cups-upgrade-required - TLS upgrade required
IPP_STATUS_ERROR_DEVICE | server-error-device-error
IPP_STATUS_ERROR_DOCUMENT_ACCESS | client-error-document-access-error
IPP_STATUS_ERROR_DOCUMENT_FORMAT_ERROR | client-error-document-format-error
IPP_STATUS_ERROR_DOCUMENT_FORMAT_NOT_SUPPORTED | client-error-document-format-not-supported
IPP_STATUS_ERROR_DOCUMENT_PASSWORD | client-error-document-password-error
IPP_STATUS_ERROR_DOCUMENT_PERMISSION | client-error-document-permission-error
IPP_STATUS_ERROR_DOCUMENT_SECURITY | client-error-document-security-error
IPP_STATUS_ERROR_DOCUMENT_UNPRINTABLE | client-error-document-unprintable-error
IPP_STATUS_ERROR_FORBIDDEN | client-error-forbidden
IPP_STATUS_ERROR_GONE | client-error-gone
IPP_STATUS_ERROR_IGNORED_ALL_SUBSCRIPTIONS | client-error-ignored-all-subscriptions
IPP_STATUS_ERROR_INTERNAL | server-error-internal-error
IPP_STATUS_ERROR_JOB_CANCELED | server-error-job-canceled
IPP_STATUS_ERROR_MULTIPLE_JOBS_NOT_SUPPORTED | server-error-multiple-document-jobs-not-supported
IPP_STATUS_ERROR_NOT_ACCEPTING_JOBS | server-error-not-accepting-jobs
IPP_STATUS_ERROR_NOT_AUTHENTICATED | client-error-not-authenticated
IPP_STATUS_ERROR_NOT_AUTHORIZED | client-error-not-authorized
IPP_STATUS_ERROR_NOT_FETCHABLE | client-error-not-fetchable
IPP_STATUS_ERROR_NOT_FOUND | client-error-not-found
IPP_STATUS_ERROR_NOT_POSSIBLE | client-error-not-possible
IPP_STATUS_ERROR_OPERATION_NOT_SUPPORTED | server-error-operation-not-supported
IPP_STATUS_ERROR_PRINTER_IS_DEACTIVATED | server-error-printer-is-deactivated
IPP_STATUS_ERROR_REQUEST_ENTITY | client-error-request-entity-too-large
IPP_STATUS_ERROR_REQUEST_VALUE | client-error-request-value-too-long
IPP_STATUS_ERROR_SERVICE_UNAVAILABLE | server-error-service-unavailable
IPP_STATUS_ERROR_TEMPORARY | server-error-temporary-error
IPP_STATUS_ERROR_TIMEOUT | client-error-timeout
IPP_STATUS_ERROR_TOO_MANY_DOCUMENTS | server-error-too-many-documents
IPP_STATUS_ERROR_TOO_MANY_JOBS | server-error-too-many-jobs
IPP_STATUS_ERROR_TOO_MANY_SUBSCRIPTIONS | client-error-too-many-subscriptions
IPP_STATUS_ERROR_URI_SCHEME | client-error-uri-scheme-not-supported
IPP_STATUS_ERROR_VERSION_NOT_SUPPORTED | server-error-version-not-supported
IPP_STATUS_OK | successful-ok
IPP_STATUS_OK_CONFLICTING | successful-ok-conflicting-attributes
IPP_STATUS_OK_EVENTS_COMPLETE | successful-ok-events-complete
IPP_STATUS_OK_IGNORED_OR_SUBSTITUTED | successful-ok-ignored-or-substituted-attributes
IPP_STATUS_OK_IGNORED_SUBSCRIPTIONS | successful-ok-ignored-subscriptions
IPP_STATUS_OK_TOO_MANY_EVENTS | successful-ok-too-many-events

### ipp_tag_e

Value and group tag values for attributes

#### Constants

IPP_TAG_ADMINDEFINE | Admin-defined value
IPP_TAG_BOOLEAN | Boolean value
IPP_TAG_CHARSET | Character set value
IPP_TAG_CUPS_INVALID | Invalid tag name for `ippTagValue`
IPP_TAG_DATE | Date/time value
IPP_TAG_DEFAULT | Default value
IPP_TAG_DELETEATTR | Delete-attribute value
IPP_TAG_DOCUMENT | Document group
IPP_TAG_END | End-of-attributes
IPP_TAG_ENUM | Enumeration value
IPP_TAG_EVENT_NOTIFICATION | Event group
IPP_TAG_INTEGER | Integer value
IPP_TAG_JOB | Job group
IPP_TAG_KEYWORD | Keyword value
IPP_TAG_LANGUAGE | Language value
IPP_TAG_MIMETYPE | MIME media type value
IPP_TAG_NAME | Name value
IPP_TAG_NAMELANG | Name-with-language value
IPP_TAG_NOTSETTABLE | Not-settable value
IPP_TAG_NOVALUE | No-value value
IPP_TAG_OPERATION | Operation group
IPP_TAG_PRINTER | Printer group
IPP_TAG_RANGE | Range value
IPP_TAG_RESOLUTION | Resolution value
IPP_TAG_RESOURCE | Resource group
IPP_TAG_STRING | Octet string value
IPP_TAG_SUBSCRIPTION | Subscription group
IPP_TAG_SYSTEM | System group
IPP_TAG_TEXT | Text value
IPP_TAG_TEXTLANG | Text-with-language value
IPP_TAG_UNKNOWN | Unknown value
IPP_TAG_UNSUPPORTED_GROUP | Unsupported attributes group
IPP_TAG_UNSUPPORTED_VALUE | Unsupported value
IPP_TAG_URI | URI value
IPP_TAG_URISCHEME | URI scheme value
IPP_TAG_ZERO | Zero tag - used for separators