[userboot] provide a mini-printf-to-log utility

Change-Id: Id7a5d80899b61dd59356c1051801fdda3262f4a6

system/core/userboot/util.c

@@ -37,8 +37,6 @@ void print(mx_handle_t log, const char* s, ...) {
     } while (s != NULL);
     va_end(ap);
 
-    *p = '\0';
-
     if (log == MX_HANDLE_INVALID) {
         mx_debug_write(buffer, p - buffer);
     } else {
@@ -52,3 +50,126 @@ void fail(mx_handle_t log, mx_status_t status, const char* msg) {
     print(log, msg, NULL);
     mx_process_exit(status);
 }
+
+static char* hexstring(char* s, size_t len, uint64_t n) {
+    char tmp[16];
+    char* hex = tmp;
+    do {
+        *hex++ = "0123456789abcdef"[n & 15];
+        n >>= 4;
+    } while (n);
+
+    while ((hex > tmp) && (len > 0)) {
+        *s++ = *--hex;
+        len--;
+    }
+    return s;
+}
+
+static char* u64string(char* s, size_t len, uint64_t n) {
+    char tmp[21]; // strlen(maxint64) + 1
+    char* dec = tmp;
+    do {
+        *dec++ = "0123456789"[n % 10];
+        n /= 10;
+    } while (n > 0);
+
+    while ((dec > tmp) && (len > 0)) {
+        *s++ = *--dec;
+        len--;
+    }
+    return s;
+}
+
+static char* i64string(char* s, size_t len, int64_t n) {
+    if (n < 0) {
+        // this will never be called with len < 1 so we
+        // don't need to check for len
+        n = -n;
+        *s++ = '-';
+        len--;
+    }
+    return u64string(s, len, n);
+}
+
+void vprintl(mx_handle_t log, const char* fmt, va_list ap) {
+    char buffer[MX_LOG_RECORD_MAX - sizeof(mx_log_record_t)];
+    static_assert(sizeof(LOG_PREFIX) < sizeof(buffer), "buffer too small");
+
+    memcpy(buffer, LOG_PREFIX, sizeof(LOG_PREFIX) - 1);
+    char* p = &buffer[sizeof(LOG_PREFIX) - 1];
+
+    size_t avail;
+    const char* s;
+    uint64_t n;
+    int64_t i;
+
+    while (*fmt && (avail = (size_t)(&buffer[sizeof(buffer)] - p))) {
+        if (*fmt != '%') {
+            *p++ = *fmt++;
+            continue;
+        }
+        switch (*++fmt) {
+        case 's':
+            s = va_arg(ap, const char*);
+            while (avail && *s) {
+                *p++ = *s++;
+                avail--;
+            }
+            break;
+        case 'z':
+            fmt++;
+            switch (*fmt) {
+            case 'u':
+                n = va_arg(ap, uint64_t);
+                goto u64print;
+            case 'd':
+                i = va_arg(ap, int64_t);
+                goto i64print;
+            case 'x':
+                n = va_arg(ap, uint64_t);
+                goto x64print;
+            default:
+                goto bad_format;
+            }
+            break;
+        case 'p':
+            n = va_arg(ap, uint64_t);
+            goto x64print;
+        case 'u':
+            n = va_arg(ap, uint32_t);
+u64print:
+            p = u64string(p, avail, n);
+            break;
+        case 'd':
+            i = va_arg(ap, int32_t);
+i64print:
+            p = i64string(p, avail, i);
+            break;
+        case 'x':
+            n = va_arg(ap, uint32_t);
+x64print:
+            p = hexstring(p, avail, n);
+            break;
+        default:
+bad_format:
+            printl(log, "printl: invalid fmt char 0x%x", *fmt);
+            mx_process_exit(-1);
+        }
+        fmt++;
+    }
+
+done:
+    if ((log == MX_HANDLE_INVALID) ||
+        (mx_log_write(log, p - buffer, buffer, 0) != MX_OK)) {
+        mx_debug_write(buffer, p - buffer);
+        mx_debug_write("\n", 1);
+    }
+}
+
+void printl(mx_handle_t log, const char* fmt, ...) {
+    va_list ap;
+    va_start(ap, fmt);
+    vprintl(log, fmt, ap);
+    va_end(ap);
+}

system/core/userboot/util.h

@@ -6,8 +6,14 @@
 
 #pragma GCC visibility push(hidden)
 
+#include <stdarg.h>
 #include <magenta/types.h>
 
+// printl() is printf-like, understanding %s %p %d %u %x %zu %zd %zx.
+// No other formatting features are supported.
+void printl(mx_handle_t log, const char* fmt, ...);
+void vprintl(mx_handle_t log, const char* fmt, va_list ap);
+
 void print(mx_handle_t log, const char* s, ...) __attribute__((sentinel));
 _Noreturn void fail(mx_handle_t log, mx_status_t status, const char* msg);