git_mkstemps_mode(): replace magic numbers with computed value

The magic number "6" appears several times in the function, and is
related to the size of the "XXXXXX" string we expect to find in the
template. Let's pull that "XXXXXX" into a constant array, whose size we
can get at compile time with ARRAY_SIZE().

Note that we probably can't just change this value, since callers will
be feeding us a certain number of X's, but it hopefully makes the
function itself easier to follow.

While we're here, let's do the same with the "letters" array (which we
_could_ modify if we wanted to include more characters).

Signed-off-by: Jeff King <peff@peff.net>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

diff --git a/wrapper.c b/wrapper.c
index 54541386c15aa2a76f8ea71116951debe392e24c..75992cff02d2ec00f48d7ded0b3fff1e01e769c4 100644 (file)
--- a/wrapper.c
+++ b/wrapper.c
@@ -478,7 +478,9 @@ int git_mkstemps_mode(char *pattern, int suffix_len, int mode)
                "abcdefghijklmnopqrstuvwxyz"
                "ABCDEFGHIJKLMNOPQRSTUVWXYZ"
                "0123456789";
-       static const int num_letters = 62;
+       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;
        uint64_t value;
        struct timeval tv;
        char *filename_template;
@@ -487,12 +489,12 @@ int git_mkstemps_mode(char *pattern, int suffix_len, int mode)
 
        len = strlen(pattern);
 
-       if (len < 6 + suffix_len) {
+       if (len < num_x + suffix_len) {
                errno = EINVAL;
                return -1;
        }
 
-       if (strncmp(&pattern[len - 6 - suffix_len], "XXXXXX", 6)) {
+       if (strncmp(&pattern[len - num_x - suffix_len], x_pattern, num_x)) {
                errno = EINVAL;
                return -1;
        }
@@ -503,12 +505,12 @@ int git_mkstemps_mode(char *pattern, int suffix_len, int mode)
         */
        gettimeofday(&tv, NULL);
        value = ((uint64_t)tv.tv_usec << 16) ^ tv.tv_sec ^ getpid();
-       filename_template = &pattern[len - 6 - suffix_len];
+       filename_template = &pattern[len - num_x - suffix_len];
        for (count = 0; count < TMP_MAX; ++count) {
                uint64_t v = value;
                int i;
                /* Fill in the random bits. */
-               for (i = 0; i < 6; i++) {
+               for (i = 0; i < num_x; i++) {
                        filename_template[i] = letters[v % num_letters];
                        v /= num_letters;
                }