Function snprintf

libs/libc/stdio/lib_snprintf.c:37–76

 ****************************************************************************/

int snprintf(FAR char *buf, size_t size, FAR const IPTR char *format, ...)
{
  union
  {
    struct lib_outstream_s    nulloutstream;
    struct lib_memoutstream_s memoutstream;
  } u;

  FAR struct lib_outstream_s *stream;
  va_list ap;
  int n;

  /* "If the value of [size] is zero on a call to snprintf(), nothing shall
   *  be written, the number of bytes that would have been written had [size]
   *  been sufficiently large excluding the terminating null shall be
   *  returned, and [buf] may be a null pointer." -- opengroup.org
   */

  if (size > 0)
    {
      /* Initialize a memory stream to write to the buffer */

      lib_memoutstream(&u.memoutstream, buf, size);
      stream = &u.memoutstream.common;
    }
  else
    {
      /* Use a null stream to get the size of the buffer */

      lib_nulloutstream(&u.nulloutstream);
      stream = &u.nulloutstream;
    }

  /* Then let lib_vsprintf do the real work */

  va_start(ap, format);
  n = lib_vsprintf(stream, format, ap);
  va_end(ap);
  return n;
}