- We use a clever algorithm to get hard-to-predict names. */
-static int
-gen_tempname (char *tmpl)
-{
- int len;
- char *XXXXXX;
- static uint64_t value;
- uint64_t random_time_bits;
- unsigned int count;
- int fd = -1;
- int save_errno = errno;
-
- /* A lower bound on the number of temporary files to attempt to
- generate. The maximum total number of temporary file names that
- can exist for a given template is 62**6. It should never be
- necessary to try all these combinations. Instead if a reasonable
- number of names is tried (we define reasonable as 62**3) fail to
- give the system administrator the chance to remove the problems. */
-#define ATTEMPTS_MIN (62 * 62 * 62)
-
- /* The number of times to attempt to generate a temporary file. To
- conform to POSIX, this must be no smaller than TMP_MAX. */
-#if ATTEMPTS_MIN < TMP_MAX
- unsigned int attempts = TMP_MAX;
-#else
- unsigned int attempts = ATTEMPTS_MIN;
-#endif
-
- len = strlen (tmpl);
- if (len < 6 || strcmp (&tmpl[len - 6], "XXXXXX"))
- {
- __set_errno (EINVAL);
- return -1;
- }
-
- /* This is where the Xs start. */
- XXXXXX = &tmpl[len - 6];
-
- /* Get some more or less random data. */
-#ifdef RANDOM_BITS
- RANDOM_BITS (random_time_bits);
-#else
-# if HAVE_GETTIMEOFDAY || _LIBC
- {
- struct timeval tv;
- __gettimeofday (&tv, NULL);
- random_time_bits = ((uint64_t) tv.tv_usec << 16) ^ tv.tv_sec;
- }
-# else
- random_time_bits = time (NULL);
-# endif
-#endif
- value += random_time_bits ^ __getpid ();
-
- for (count = 0; count < attempts; value += 7777, ++count)
- {
- uint64_t v = value;
-
- /* Fill in the random bits. */
- XXXXXX[0] = letters[v % 62];
- v /= 62;
- XXXXXX[1] = letters[v % 62];
- v /= 62;
- XXXXXX[2] = letters[v % 62];
- v /= 62;
- XXXXXX[3] = letters[v % 62];
- v /= 62;
- XXXXXX[4] = letters[v % 62];
- v /= 62;
- XXXXXX[5] = letters[v % 62];
-
- fd = __mkdir (tmpl, S_IRUSR | S_IWUSR | S_IXUSR);
-
- if (fd >= 0)
- {
- __set_errno (save_errno);
- return fd;
- }
- else if (errno != EEXIST)
- return -1;
- }
-
- /* We got out of the loop because we ran out of combinations to try. */
- __set_errno (EEXIST);
- return -1;
-}