flate

commit 7f256464f678d5bd8c3bd823882a80b5bb24054b
parent 29637fae613ae2ef326c64b4270ade27ea1ca61f
Author: nsz <nszabolcs@gmail.com>
Date:   Wed, 22 Apr 2009 13:28:13 +0200

-dstbegin
Diffstat:
inflate_simple.c
 | 
33
+++++++++------------------------

1 file changed, 9 insertions(+), 24 deletions(-)
diff --git a/inflate_simple.c b/inflate_simple.c
@@ -20,9 +20,7 @@ typedef struct {
 
 typedef struct {
 	uchar *src;
-
 	uchar *dst;
-	uchar *dstbegin;
 
 	uint bits;
 	uint nbits;
@@ -35,11 +33,11 @@ typedef struct {
 static HuffTree ltree; /* fixed lit/len tree */
 static HuffTree dtree; /* fixed distance tree */
 
-/* base offsets */
+/* base offset tables */
 static ushort lenbase[Nlen];
 static ushort distbase[Ndist];
 
-/* extra bits */
+/* extra bits tables */
 static uchar lenbits[Nlen] = {
 	0,  0,  0,  0,  0,  0,  0,  0,  1,  1,
 	1,  1,  2,  2,  2,  2,  3,  3,  3,  3,
@@ -65,7 +63,6 @@ static void init_base_tables(void) {
 		base += 1 << lenbits[i];
 	}
 	lenbase[Nlen-1]--; /* deflate bug */
-	
 	for (base = 1, i = 0; i < Ndist; i++) {
 		distbase[i] = base;
 		base += 1 << distbits[i];
@@ -86,7 +83,6 @@ static void init_fixed_trees(void) {
 		ltree.symbol[24 + 144 + i] = 280 + i;
 	for (i = 0; i < 112; i++)
 		ltree.symbol[24 + 144 + 8 + i] = 144 + i;
-
 	dtree.count[5] = Ndist;
 	for (i = 0; i < Ndist; i++)
 		dtree.symbol[i] = i;
@@ -97,19 +93,16 @@ static void build_tree(HuffTree *t, const uchar *lens, int n) {
 	int offs[HuffBits];
 	int i, sum;
 
+	/* count code lengths and calc first code (offs) for each length */
 	for (i = 0; i < HuffBits; i++)
 		t->count[i] = 0;
-
-	/* count code lengths and calc first code for each length */
 	for (i = 0; i < n; i++)
 		t->count[lens[i]]++;
 	t->count[0] = 0;
-
 	for (sum = 0, i = 0; i < HuffBits; i++) {
 		offs[i] = sum;
 		sum += t->count[i];
 	}
-
 	/* sort symbols by code length */
 	for (i = 0; i < n; i++)
 		if (lens[i])
@@ -166,14 +159,12 @@ static void decode_trees(FlateStream *s, HuffTree *lt, HuffTree *dt) {
 	nlit = 257 + getbits(s, 5);
 	ndist = 1 + getbits(s, 5);
 	nclen = 4 + getbits(s, 4);
-
 	/* build code length tree */
 	for (i = 0; i < Nclen; i++)
 		lens[i] = 0;
 	for (i = 0; i < nclen; i++)
 		lens[clenorder[i]] = getbits(s, 3);
 	build_tree(&ctree, lens, Nclen);
-
 	/* decode code lengths for the dynamic trees */
 	for (i = 0; i < nlit + ndist; ) {
 		uint sym = decode_symbol(s, &ctree);
@@ -208,7 +199,6 @@ static void decode_block(FlateStream *s, HuffTree *lt, HuffTree *dt) {
 
 	for (;;) {
 		sym = decode_symbol(s, lt);
-
 		if (sym == 256)
 			return;
 		if (sym < 256)
@@ -234,10 +224,7 @@ static void inflate_uncompressed_block(FlateStream *s) {
 
 	len = (s->src[1] << 8) | s->src[0];
 	s->src += 4;
-
-	/* start next block on a byte boundary */
-	s->nbits = 0;
-
+	s->nbits = 0; /* start next block on a byte boundary */
 	while (len--)
 		*s->dst++ = *s->src++;
 }
@@ -260,21 +247,19 @@ void inflate_init(void) {
 	init_base_tables();
 }
 
-/* inflate stream from src to dst */
-uint inflate(void *dst, void *src) {
+/* inflate stream from src to dst, return end pointer */
+void *inflate(void *dst, void *src) {
 	FlateStream s;
 	uint final;
 
 	s.src = src;
-	s.dst = s.dstbegin = dst;
+	s.dst = dst;
 	s.nbits = 0;
 	do {
 		uint blocktype;
 
 		final = getbit(&s);
 		blocktype = getbits(&s, 2);
-
-		/* decompress block */
 		switch (blocktype) {
 		case 0:
 			inflate_uncompressed_block(&s);
@@ -287,7 +272,7 @@ uint inflate(void *dst, void *src) {
 			break;
 		}
 	} while (!final);
-	return s.dst - s.dstbegin;
+	return s.dst;
 }
 
 
@@ -313,7 +298,7 @@ int main(int argc, char **argv) {
 	inflate_init();
 	src = readall(argc < 2 ? stdin : fopen(argv[1], "r"));
 	dst = malloc(len);
-	len = inflate(dst, src);
+	len = (uchar *)inflate(dst, src) - dst;
 	fprintf(stderr, "inflate_simple: uncompressed %u bytes\n", len);
 	fwrite(dst, 1, len, stdout);
 	free(dst);