From: Nicolas Pitre <nico@cam.org>
Date: Sat, 18 Mar 2006 03:45:07 +0000 (-0500)
Subject: 3% tighter packs for free
X-Git-Tag: v1.3.0-rc1~22^2
X-Git-Url: https://git.octo.it/?a=commitdiff_plain;h=5a1fb2ca92caaa7ae9044ab81dc102f59d17b97a;p=git.git

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 aaee7be4..1188b31c 100644
--- 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;
 			}