flate

commit 91bbf2dbb704b4556c627c7f5a6d4651a1c7a613
parent a134df0ce7efca5185cfaaf05c54e250fbc5bc59
Author: nsz <nszabolcs@gmail.com>
Date:   Tue, 11 Aug 2009 09:53:43 +0200

deflate match modification
Diffstat:
deflate.c
 | 
22
+++++++++++-----------

1 file changed, 11 insertions(+), 11 deletions(-)
diff --git a/deflate.c b/deflate.c
@@ -483,28 +483,27 @@ static void recordlit(State *s, int c) {
 }
 
 /* multiplicative hash */
-static ushort gethash(uchar *p) {
+static int gethash(uchar *p) {
 	return (0x9e3779b1 * ((p[0]<<16) + (p[1]<<8) + p[2]) >> (32 - HashBits)) % HashSize;
 }
 
-static ushort updatechain(State *s) {
-	ushort i, h;
+static int updatechain(State *s) {
+	int h, i;
 
 	if (s->avail < MinMatch)
 		return 0;
 	h = gethash(s->win + s->pos);
 	i = s->head[h];
 	s->head[h] = s->pos;
-	s->chain[s->pos % MaxDist] = i;
 	if (i >= s->pos || s->pos - i >= MaxDist)
-		return 0;
+		i = 0;
+	s->chain[s->pos % MaxDist] = i;
 	return i;
 }
 
 static Match getmatch(State *s, int mpos) {
 	Match m = {0, MinMatch-1};
 	int len;
-	int maxlen = s->avail < MaxMatch ? s->avail : MaxMatch;
 	int limit = s->pos - MaxDist;
 	int chainlen = MaxChainLen;
 	uchar *q;
@@ -514,21 +513,22 @@ static Match getmatch(State *s, int mpos) {
 	do {
 		q = s->win + mpos;
 		/* at least m.len+1 long */
-		if (q[m.len] != p[m.len] || q[0] != p[0])
+		if (q[m.len] != p[m.len] || q[m.len-1] != p[m.len-1] || q[0] != p[0])
 			continue;
-		/* loop unroll: MaxMatch % 10 == 8, overflow if avail < MaxMatch */
-		/* only little gain over while (++p != end && *++q == *p); */
+		/* loop unroll: MaxMatch % 10 == 8, overflow if avail < MaxMatch, only little gain
 		do; while (*++q == *++p && *++q == *++p
 		        && *++q == *++p && *++q == *++p
 		        && *++q == *++p && *++q == *++p
 		        && *++q == *++p && ++p != end && *++q == *p
 		        && *++q == *++p && *++q == *++p);
+		*/
+		while (++p != end && *++q == *p);
 		len = MaxMatch - (end - p);
 		p -= len;
 		if (len > m.len) {
 			m.dist = s->pos - mpos;
-			if (len >= maxlen) {
-				m.len = maxlen;
+			if (len >= s->avail || len == MaxMatch) {
+				m.len = s->avail < MaxMatch ? s->avail : MaxMatch;
 				return m;
 			}
 			m.len = len;