Paul Eggert <egg...@cs.ucla.edu> (08/02/2012): > Thanks very much for the patch. But can someone who's looked into it > please explain why 'window' needs to be zeroed out? This will save me > time in reviewing the patch. Thanks.
Welcome. Here's a slightly more detailed analysis. You can find attached the sample files I used (still from the ppl source package). I managed to track it down to deflate() (what a surprise!), so I decided to check the matches. Printing match_length only led me to a single difference, while printing both match_length and match_start (which according to a comment is set by longest_match()), I got two differences. To produce the below-quoted diff, using the attached patch, I did: | tar xfz ppl.tar.gz | gzip -9f README CREDITS > match-2 | tar xfz ppl.tar.gz | gzip -9f CREDITS > match-1 | diff -u match-2 match-1 Of course there's an extra file showing up in the diff, but skipping it, here's the diff: | match: 46 @ 19459 | match: 8 @ 15659 | match: 8 @ 15659 | -match: 7 @ 17193 | -match: 6 @ 17193 | +match: 6 @ 19510 | +match: 6 @ 19510 | [ no more matches ] Interestingly, the size of the CREDITS file is 19579. Mraw, KiBi.
From cbe288044df0e149e6da3744f89eb49ce32e6c2a Mon Sep 17 00:00:00 2001
From: Cyril Brulebois <k...@debian.org>
Date: Mon, 13 Feb 2012 01:31:36 +0100
Subject: [PATCH] Pin-point dirty window bug.
---
deflate.c | 1 +
1 files changed, 1 insertions(+), 0 deletions(-)
diff --git a/deflate.c b/deflate.c
index 1b3ac52..606a2e5 100644
--- a/deflate.c
+++ b/deflate.c
@@ -757,6 +757,7 @@ off_t deflate()
*/
match_length = longest_match (hash_head);
/* longest_match() sets match_start */
+ printf("match: %u @ %u\n", match_length, match_start);
if (match_length > lookahead) match_length = lookahead;
/* Ignore a length 3 match if it is too distant: */
--
1.7.9
ppl.tar.gz
Description: Binary data
signature.asc
Description: Digital signature
