compat/snprintf.c

   1 #include "../git-compat-util.h"
   2
   3 /*
   4  * The size parameter specifies the available space, i.e. includes
   5  * the trailing NUL byte; but Windows's vsnprintf uses the entire
   6  * buffer and avoids the trailing NUL, should the buffer be exactly
   7  * big enough for the result. Defining SNPRINTF_SIZE_CORR to 1 will
   8  * therefore remove 1 byte from the reported buffer size, so we
   9  * always have room for a trailing NUL byte.
  10  */
  11 #ifndef SNPRINTF_SIZE_CORR
  12 #if defined(WIN32) && (!defined(__GNUC__) || __GNUC__ < 4)
  13 #define SNPRINTF_SIZE_CORR 1
  14 #else
  15 #define SNPRINTF_SIZE_CORR 0
  16 #endif
  17 #endif
  18
  19 #undef vsnprintf
  20 int git_vsnprintf(char *str, size_t maxsize, const char *format, va_list ap)
  21 {
  22         char *s;
  23         int ret = -1;
  24
  25         if (maxsize > 0) {
  26                 ret = vsnprintf(str, maxsize-SNPRINTF_SIZE_CORR, format, ap);
  27                 if (ret == maxsize-1)
  28                         ret = -1;
  29                 /* Windows does not NUL-terminate if result fills buffer */
  30                 str[maxsize-1] = 0;
  31         }
  32         if (ret != -1)
  33                 return ret;
  34
  35         s = NULL;
  36         if (maxsize < 128)
  37                 maxsize = 128;
  38
  39         while (ret == -1) {
  40                 maxsize *= 4;
  41                 str = realloc(s, maxsize);
  42                 if (! str)
  43                         break;
  44                 s = str;
  45                 ret = vsnprintf(str, maxsize-SNPRINTF_SIZE_CORR, format, ap);
  46                 if (ret == maxsize-1)
  47                         ret = -1;
  48         }
  49         free(s);
  50         return ret;
  51 }
  52
  53 int git_snprintf(char *str, size_t maxsize, const char *format, ...)
  54 {
  55         va_list ap;
  56         int ret;
  57
  58         va_start(ap, format);
  59         ret = git_vsnprintf(str, maxsize, format, ap);
  60         va_end(ap);
  61
  62         return ret;
  63 }
  64