return ret;
}
+/*
+ * Return the slot of the most-significant bit set in "val". There are various
+ * ways to do this quickly with fls() or __builtin_clzl(), but speed is
+ * probably not a big deal here.
+ */
+static unsigned msb(unsigned long val)
+{
+ unsigned r = 0;
+ while (val >>= 1)
+ r++;
+ return r;
+}
+
int find_unique_abbrev_r(char *hex, const unsigned char *sha1, int len)
{
int status, exists;
+ if (len < 0) {
+ unsigned long count = approximate_object_count();
+ /*
+ * Add one because the MSB only tells us the highest bit set,
+ * not including the value of all the _other_ bits (so "15"
+ * is only one off of 2^4, but the MSB is the 3rd bit.
+ */
+ len = msb(count) + 1;
+ /*
+ * We now know we have on the order of 2^len objects, which
+ * expects a collision at 2^(len/2). But we also care about hex
+ * chars, not bits, and there are 4 bits per hex. So all
+ * together we need to divide by 2; but we also want to round
+ * odd numbers up, hence adding one before dividing.
+ */
+ len = (len + 1) / 2;
+ /*
+ * For very small repos, we stick with our regular fallback.
+ */
+ if (len < FALLBACK_DEFAULT_ABBREV)
+ len = FALLBACK_DEFAULT_ABBREV;
+ }
+
sha1_to_hex_r(hex, sha1);
if (len == 40 || !len)
return 40;
const char *find_unique_abbrev(const unsigned char *sha1, int len)
{
- static char hex[GIT_SHA1_HEXSZ + 1];
+ static int bufno;
+ static char hexbuffer[4][GIT_SHA1_HEXSZ + 1];
+ char *hex = hexbuffer[3 & ++bufno];
find_unique_abbrev_r(hex, sha1, len);
return hex;
}