From: Mika Lindqvist <postmaster@raasu.org>
Date: Fri, 17 Mar 2017 19:36:38 +0000 (+0200)
Subject: deflate_medium: Make sure we have enough lookahead before trying to scan for matches.
X-Git-Tag: 1.9.9-b1~661
X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=75e76eebeb08dccea44a1d9933699f7f9a0a97ea;p=thirdparty%2Fzlib-ng.git

deflate_medium: Make sure we have enough lookahead before trying to scan for matches.
* longest_match: Abort if match is in future
---

diff --git a/deflate_medium.c b/deflate_medium.c
index 972f5a840..2a12d4bfd 100644
--- a/deflate_medium.c
+++ b/deflate_medium.c
@@ -264,7 +264,7 @@ block_state deflate_medium(deflate_state *s, int flush) {
         insert_match(s, current_match);
 
         /* now, look ahead one */
-        if (s->lookahead > MIN_LOOKAHEAD) {
+        if (s->lookahead > MIN_LOOKAHEAD && (current_match.strstart + current_match.match_length) < (s->window_size - MIN_LOOKAHEAD)) {
             s->strstart = current_match.strstart + current_match.match_length;
             hash_head = insert_string(s, s->strstart, 1);
 
diff --git a/match.c b/match.c
index 87e3d9655..b731246c0 100644
--- a/match.c
+++ b/match.c
@@ -84,7 +84,9 @@ ZLIB_INTERNAL unsigned longest_match(deflate_state *const s, IPos cur_match) {
 
     Assert((unsigned long)s->strstart <= s->window_size - MIN_LOOKAHEAD, "need lookahead");
     do {
-        Assert(cur_match < s->strstart, "no future");
+        if (cur_match >= s->strstart) {
+          break;
+        }
         match = s->window + cur_match;
 
         /*
@@ -203,7 +205,9 @@ ZLIB_INTERNAL unsigned longest_match(deflate_state *const s, IPos cur_match) {
     Assert((unsigned long)s->strstart <= s->window_size - MIN_LOOKAHEAD, "need lookahead");
     do {
         unsigned char *match;
-        Assert(cur_match < s->strstart, "no future");
+        if (cur_match >= s->strstart) {
+          break;
+        }
         match = s->window + cur_match;
 
         /*
@@ -375,7 +379,9 @@ ZLIB_INTERNAL unsigned longest_match(deflate_state *const s, IPos cur_match) {
     Assert((unsigned long)s->strstart <= s->window_size-MIN_LOOKAHEAD, "need lookahead");
 
     do {
-        Assert(cur_match < s->strstart, "no future");
+        if (cur_match >= s->strstart) {
+          break;
+        }
 
         /* Skip to next match if the match length cannot increase
          * or if the match length is less than 2.  Note that the checks below