Function git_mkdstemps_mode

wrapper.c:436–494

* Returns -1 on error, 0 if it created a directory, or an open file * descriptor to the created regular file. */

 * descriptor to the created regular file.
 */
static int git_mkdstemps_mode(char *pattern, int suffix_len, int mode, bool dir)
{
	static const char letters[] =
		"abcdefghijklmnopqrstuvwxyz"
		"ABCDEFGHIJKLMNOPQRSTUVWXYZ"
		"0123456789";
	static const int num_letters = ARRAY_SIZE(letters) - 1;
	static const char x_pattern[] = "XXXXXX";
	static const int num_x = ARRAY_SIZE(x_pattern) - 1;
	char *filename_template;
	size_t len;
	int fd, count;

	len = strlen(pattern);

	if (len < num_x + suffix_len) {
		errno = EINVAL;
		return -1;
	}

	if (strncmp(&pattern[len - num_x - suffix_len], x_pattern, num_x)) {
		errno = EINVAL;
		return -1;
	}

	/*
	 * Replace pattern's XXXXXX characters with randomness.
	 * Try TMP_MAX different filenames.
	 */
	filename_template = &pattern[len - num_x - suffix_len];
	for (count = 0; count < TMP_MAX; ++count) {
		int i;
		uint64_t v;
		if (csprng_bytes(&v, sizeof(v), 0) < 0)
			return error_errno("unable to get random bytes for temporary file");

		/* Fill in the random bits. */
		for (i = 0; i < num_x; i++) {
			filename_template[i] = letters[v % num_letters];
			v /= num_letters;
		}

		if (dir)
			fd = mkdir(pattern, mode);
		else
			fd = open(pattern, O_CREAT | O_EXCL | O_RDWR, mode);
		if (fd >= 0)
			return fd;
		/*
		 * Fatal error (EPERM, ENOSPC etc).
		 * It doesn't make sense to loop.
		 */
		if (errno != EEXIST)
			break;
	}
	/* We return the null string if we can't find a unique file name.  */
	pattern[0] = '\0';
	return -1;