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-rw-r--r--compat/mkstemps.c70
1 files changed, 70 insertions, 0 deletions
diff --git a/compat/mkstemps.c b/compat/mkstemps.c
new file mode 100644
index 0000000000..14179c8e6d
--- /dev/null
+++ b/compat/mkstemps.c
@@ -0,0 +1,70 @@
+#include "../git-compat-util.h"
+
+/* Adapted from libiberty's mkstemp.c. */
+
+#undef TMP_MAX
+#define TMP_MAX 16384
+
+int gitmkstemps(char *pattern, int suffix_len)
+{
+ static const char letters[] =
+ "abcdefghijklmnopqrstuvwxyz"
+ "ABCDEFGHIJKLMNOPQRSTUVWXYZ"
+ "0123456789";
+ static const int num_letters = 62;
+ uint64_t value;
+ struct timeval tv;
+ char *template;
+ size_t len;
+ int fd, count;
+
+ len = strlen(pattern);
+
+ if (len < 6 + suffix_len) {
+ errno = EINVAL;
+ return -1;
+ }
+
+ if (strncmp(&pattern[len - 6 - suffix_len], "XXXXXX", 6)) {
+ errno = EINVAL;
+ return -1;
+ }
+
+ /*
+ * Replace pattern's XXXXXX characters with randomness.
+ * Try TMP_MAX different filenames.
+ */
+ gettimeofday(&tv, NULL);
+ value = ((size_t)(tv.tv_usec << 16)) ^ tv.tv_sec ^ getpid();
+ template = &pattern[len - 6 - suffix_len];
+ for (count = 0; count < TMP_MAX; ++count) {
+ uint64_t v = value;
+ /* Fill in the random bits. */
+ template[0] = letters[v % num_letters]; v /= num_letters;
+ template[1] = letters[v % num_letters]; v /= num_letters;
+ template[2] = letters[v % num_letters]; v /= num_letters;
+ template[3] = letters[v % num_letters]; v /= num_letters;
+ template[4] = letters[v % num_letters]; v /= num_letters;
+ template[5] = letters[v % num_letters]; v /= num_letters;
+
+ fd = open(pattern, O_CREAT | O_EXCL | O_RDWR, 0600);
+ if (fd > 0)
+ return fd;
+ /*
+ * Fatal error (EPERM, ENOSPC etc).
+ * It doesn't make sense to loop.
+ */
+ if (errno != EEXIST)
+ break;
+ /*
+ * This is a random value. It is only necessary that
+ * the next TMP_MAX values generated by adding 7777 to
+ * VALUE are different with (module 2^32).
+ */
+ value += 7777;
+ }
+ /* We return the null string if we can't find a unique file name. */
+ pattern[0] = '\0';
+ errno = EINVAL;
+ return -1;
+}