flate

commit 0a6feb60f9b8d1f591f15692fee108f043ed2fdf
parent 3c040f8374e0155983ffe86633b6050a16b13499
Author: nsz <nszabolcs@gmail.com>
Date:   Tue, 12 May 2009 00:59:26 +0200

fix
Diffstat:
inflate.c
 | 
30
++++++++++++++----------------

1 file changed, 14 insertions(+), 16 deletions(-)
diff --git a/inflate.c b/inflate.c
@@ -17,7 +17,8 @@ enum {
 	Ndist           = 30,  /* number of distance codes */
 	Nclen           = 19,  /* number of code length codes */
 	SrcSize         = 1 << 12, /* input buffer size */
-	WinSize         = 1 << 15 /* output window size */
+	WinSize         = 1 << 15, /* output window size */
+	WinMask         = WinSize - 1 /* window pos (index) mask */
 };
 
 enum {
@@ -213,11 +214,11 @@ static int checksrc(Stream *s) {
 /* check window position before writing to it */
 static int checkpos(Stream *s) {
 	if (s->pos == WinSize) {
+		s->pos = 0;
 		if (s->w(s->win, WinSize, s->wdata) != WinSize) {
 			s->error = FlateOutError;
 			return 0;
 		}
-		s->pos = 0;
 	}
 	return 1;
 }
@@ -389,7 +390,7 @@ static void decode_block(Stream *s, Huff *lhuff, Huff *dhuff) {
 			if (!checkpos(s))
 				return;
 		} else {
-			uint i, len, dist;
+			uint len, dist;
 
 			sym -= 257;
 			if (sym >= Nlen) {
@@ -407,32 +408,31 @@ static void decode_block(Stream *s, Huff *lhuff, Huff *dhuff) {
 			dist = distbase[sym] + getbits(s, distbits[sym]);
 			if (s->error != FlateOk)
 				return;
-			/* copy match, loop unroll for common case */
+			/* copy match, loop unroll in common case */
 			if (s->pos + len <= WinSize) {
 				uint pos = s->pos;
 
-				while (len > 4) {
-					s->win[pos] = s->win[(pos - dist) & 0x7ff];
+				while (len >= 4) {
+					s->win[pos] = s->win[(pos - dist) & WinMask];
 					pos++;
-					s->win[pos] = s->win[(pos - dist) & 0x7ff];
+					s->win[pos] = s->win[(pos - dist) & WinMask];
 					pos++;
-					s->win[pos] = s->win[(pos - dist) & 0x7ff];
+					s->win[pos] = s->win[(pos - dist) & WinMask];
 					pos++;
-					s->win[pos] = s->win[(pos - dist) & 0x7ff];
+					s->win[pos] = s->win[(pos - dist) & WinMask];
 					pos++;
 					len -= 4;
 				}
-				while (len > 0) {
-					s->win[pos] = s->win[(pos - dist) & 0x7ff];
+				while (len--) {
+					s->win[pos] = s->win[(pos - dist) & WinMask];
 					pos++;
-					len--;
 				}
 				s->pos = pos;
 				if (!checkpos(s))
 					return;
 			} else {
-				for (i = 0; i < len; i++) {
-					s->win[s->pos] = s->win[(s->pos - dist) & 0x7ff];
+				while (len--) {
+					s->win[s->pos] = s->win[(s->pos - dist) & WinMask];
 					s->pos++;
 					if (!checkpos(s))
 						return;
@@ -542,7 +542,6 @@ int r(void *p, int siz, void *data) {
 	struct data *d = data;
 
 	n = fread(p, 1, siz, d->f);
-/*fprintf(stderr, "r: %u\n", n);*/
 	d->n += n;
 	return n;
 }
@@ -552,7 +551,6 @@ int w(void *p, int siz, void *data) {
 	struct data *d = data;
 
 	n = fwrite(p, 1, siz, d->f);
-/*fprintf(stderr, "w: %u\n", n);*/
 	d->n += n;
 	return n;
 }