flate

commit 91f4e002ef67509b758a6765a35bba94b13688cd
parent 2a4423264be4b26a110c77a07ccd7e108e90c22d
Author: nsz <nszabolcs@gmail.com>
Date:   Thu, 16 Jul 2009 08:03:05 +0200

better lazy match, dont allow short match with large dist
Diffstat:
deflate_simple.c
 | 
42
+++++++++++++-----------------------------

1 file changed, 13 insertions(+), 29 deletions(-)
diff --git a/deflate_simple.c b/deflate_simple.c
@@ -19,7 +19,6 @@ enum {
 	MaxChainStep = 64,
 	HashSize = 2039,
 	WinSize = 1 << 15,
-	SymSize = 1 << 16,
 
 	LzRunlen = 1<<30
 };
@@ -347,7 +346,7 @@ static void deflate_block(State *s, int blocklen) {
 	for (nclen = Nclen; nclen > 4 && clen[clenorder[nclen-1]] == 0; nclen--);
 
 	/* calc size */
-	uncsize = 3 + 4 + 8*blocklen + (16 - 3 - s->nbits)%8; /* byte aligned */
+	uncsize = 3 + 16 + 8*blocklen + (16-3-s->nbits) % 8; /* byte aligned */
 	fixsize = 3;
 	dynsize = 3 + 5 + 5 + 4;
 	dynsize += 3 * nclen;
@@ -492,6 +491,8 @@ static Match getmatch(State *s, uchar *src, int len) {
 		}
 		pos = s->chain[pos];
 	}
+	if (m.len < MinMatch || (m.len == MinMatch && m.dist > 1<<13))
+		m.len = 0;
 	return m;
 }
 
@@ -546,37 +547,20 @@ int deflate(uchar *src, int len, uchar *dst) {
 	s.src = src;
 	while (len > 0) {
 		m = getmatch(&s, src, len);
-/*
-		if (m.len >= MinMatch) {
-			recordmatch(&s, m);
-			step = m.len;
+		if (m.len > prevm.len) {
+			if (prevm.len)
+				recordlit(&s, prevc);
+			prevm = m;
+			prevc = *src;
+			step = 1;
+		} else if (prevm.len) {
+			recordmatch(&s, prevm);
+			step = prevm.len - 1;
+			prevm.len = 0;
 		} else {
 			recordlit(&s, *src);
 			step = 1;
 		}
-*/
-		if (m.len >= MinMatch)
-			if (m.len <= prevm.len) {
-				recordmatch(&s, prevm);
-				step = prevm.len - 1;
-				prevm.len = 0;
-			} else {
-				if (prevm.len > 0)
-					recordlit(&s, prevc);
-				prevm = m;
-				prevc = *src;
-				step = 1;
-			}
-		else
-			if (prevm.len > 0) {
-				recordmatch(&s, prevm);
-				step = prevm.len - 1;
-				prevm.len = 0;
-			} else {
-				recordlit(&s, *src);
-				step = 1;
-			}
-
 		while (step > 0) {
 			if (len >= MinMatch) {
 				hash = gethash(src);