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) && (!defined(_MSC_VER) || _MSC_VER < 1900)
  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         va_list cp;
  23         char *s;
  24         int ret = -1;
  25
  26         if (maxsize > 0) {
  27                 va_copy(cp, ap);
  28                 ret = vsnprintf(str, maxsize-SNPRINTF_SIZE_CORR, format, cp);
  29                 va_end(cp);
  30                 if (ret == maxsize-1)
  31                         ret = -1;
  32                 /* Windows does not NUL-terminate if result fills buffer */
  33                 str[maxsize-1] = 0;
  34         }
  35         if (ret != -1)
  36                 return ret;
  37
  38         s = NULL;
  39         if (maxsize < 128)
  40                 maxsize = 128;
  41
  42         while (ret == -1) {
  43                 maxsize *= 4;
  44                 str = realloc(s, maxsize);
  45                 if (! str)
  46                         break;
  47                 s = str;
  48                 va_copy(cp, ap);
  49                 ret = vsnprintf(str, maxsize-SNPRINTF_SIZE_CORR, format, cp);
  50                 va_end(cp);
  51                 if (ret == maxsize-1)
  52                         ret = -1;
  53         }
  54         free(s);
  55         return ret;
  56 }
  57
  58 int git_snprintf(char *str, size_t maxsize, const char *format, ...)
  59 {
  60         va_list ap;
  61         int ret;
  62
  63         va_start(ap, format);
  64         ret = git_vsnprintf(str, maxsize, format, ap);
  65         va_end(ap);
  66
  67         return ret;
  68 }
  69