71 lines
1.7 KiB
C
71 lines
1.7 KiB
C
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#include "../git-compat-util.h"
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/* Adapted from libiberty's mkstemp.c. */
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#undef TMP_MAX
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#define TMP_MAX 16384
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int gitmkstemps(char *pattern, int suffix_len)
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{
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static const char letters[] =
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"abcdefghijklmnopqrstuvwxyz"
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"ABCDEFGHIJKLMNOPQRSTUVWXYZ"
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"0123456789";
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static const int num_letters = 62;
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uint64_t value;
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struct timeval tv;
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char *template;
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size_t len;
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int fd, count;
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len = strlen(pattern);
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if (len < 6 + suffix_len) {
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errno = EINVAL;
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return -1;
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}
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if (strncmp(&pattern[len - 6 - suffix_len], "XXXXXX", 6)) {
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errno = EINVAL;
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return -1;
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}
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/*
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* Replace pattern's XXXXXX characters with randomness.
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* Try TMP_MAX different filenames.
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*/
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gettimeofday(&tv, NULL);
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value = ((size_t)(tv.tv_usec << 16)) ^ tv.tv_sec ^ getpid();
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template = &pattern[len - 6 - suffix_len];
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for (count = 0; count < TMP_MAX; ++count) {
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uint64_t v = value;
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/* Fill in the random bits. */
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template[0] = letters[v % num_letters]; v /= num_letters;
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template[1] = letters[v % num_letters]; v /= num_letters;
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template[2] = letters[v % num_letters]; v /= num_letters;
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template[3] = letters[v % num_letters]; v /= num_letters;
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template[4] = letters[v % num_letters]; v /= num_letters;
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template[5] = letters[v % num_letters]; v /= num_letters;
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fd = open(pattern, O_CREAT | O_EXCL | O_RDWR, 0600);
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if (fd > 0)
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return fd;
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/*
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* Fatal error (EPERM, ENOSPC etc).
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* It doesn't make sense to loop.
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*/
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if (errno != EEXIST)
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break;
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/*
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* This is a random value. It is only necessary that
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* the next TMP_MAX values generated by adding 7777 to
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* VALUE are different with (module 2^32).
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*/
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value += 7777;
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}
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/* We return the null string if we can't find a unique file name. */
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pattern[0] = '\0';
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errno = EINVAL;
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return -1;
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}
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