bsdiff-portable

commit 9f49f0d0b82ceb2dfd93c50cb47dcbb84f511531
parent 155669edfab02aaa2eb5e39ccd67f3e2c8e1ffb0
Author: Thieu Le <thieule@chromium.org>
Date:   Thu, 24 Sep 2020 16:52:43 +1000

Expand pathological case where files differ by <8 bytes

Modify bsdiff to better handle the case where files differ by <8 bytes
in some regions, not limitting this case to linear traversal.

Change-Id: I5b796977fc0e81d08b2e22abae48ae9e7dd2dba6
Reviewed-on: https://gerrit.chromium.org/gerrit/19270
Reviewed-by: Don Garrett <dgarrett@chromium.org>
Commit-Ready: Thieu Le <thieule@chromium.org>
Tested-by: Thieu Le <thieule@chromium.org>

Diffstat:
M
bsdiff.c
 | 
11
++++++-----

1 file changed, 6 insertions(+), 5 deletions(-)
diff --git a/bsdiff.c b/bsdiff.c
@@ -177,11 +177,12 @@ main(int argc, char **argv)
 			    old[scan + lastoffset] == new[scan])
 				oldscore--;
 
-			if (len == prev_len - 1 &&
-			    oldscore == prev_oldscore - 1 &&
-			    pos == prev_pos + 1 &&
-			    len > oldscore &&
-			    len <= oldscore + 8)
+			const off_t fuzz = 8;
+			if (prev_len - fuzz <= len && len <= prev_len &&
+			    prev_oldscore - fuzz <= oldscore &&
+			    oldscore <= prev_oldscore &&
+			    prev_pos <= pos && pos <= prev_pos + fuzz &&
+			    oldscore <= len && len <= oldscore + fuzz)
 				num_less_than_eight++;
 			else
 				num_less_than_eight = 0;