3% tighter packs for free

This patch makes for 3.4% smaller pack with the git repository, and
a bit more than 3% smaller pack with the kernel repository.

And so with _no_ measurable CPU difference.

Signed-off-by: Nicolas Pitre <nico@cam.org>
Signed-off-by: Junio C Hamano <junkio@cox.net>

diff --git a/diff-delta.c b/diff-delta.c
index aaee7be..1188b31 100644 (file)
--- a/diff-delta.c
+++ b/diff-delta.c
@@ -136,7 +136,8 @@ void *diff_delta(void *from_buf, unsigned long from_size,
                 unsigned long *delta_size,
                 unsigned long max_size)
 {
-       unsigned int i, outpos, outsize, inscnt, hash_shift;
+       unsigned int i, outpos, outsize, hash_shift;
+       int inscnt;
        const unsigned char *ref_data, *ref_top, *data, *top;
        unsigned char *out;
        struct index *entry, **hash;
@@ -222,6 +223,20 @@ void *diff_delta(void *from_buf, unsigned long from_size,
                        unsigned char *op;
 
                        if (inscnt) {
+                               while (moff && ref_data[moff-1] == data[-1]) {
+                                       if (msize == 0x10000)
+                                               break;
+                                       /* we can match one byte back */
+                                       msize++;
+                                       moff--;
+                                       data--;
+                                       outpos--;
+                                       if (--inscnt)
+                                               continue;
+                                       outpos--;  /* remove count slot */
+                                       inscnt--;  /* make it -1 */
+                                       break;
+                               }
                                out[outpos - inscnt - 1] = inscnt;
                                inscnt = 0;
                        }