flate

commit 8c0e33a192944d350098d5470a05ae72bc725c1f
parent ee5ae6647276d80f78cfa2d2110f11695c39bb3d
Author: nsz <nszabolcs@gmail.com>
Date:   Sun,  7 Jun 2009 21:57:40 +0200

separate decode_symbol_long
Diffstat:
Makefile
 | 
2
+-
inflate.c
 | 
89
++++++++++++++++++++++++++++++++++++++++---------------------------------------

2 files changed, 46 insertions(+), 45 deletions(-)
diff --git a/Makefile b/Makefile
@@ -20,7 +20,7 @@ clean:
 
 
 prof: inflate.c
-	gcc -fprofile-arcs -ftest-coverage -pg -g -Wall $<
+	gcc -O3 -fprofile-arcs -ftest-coverage -pg -g -Wall $<
 	cat a.dat | ./a.out > /dev/null
 	gcov -b $< > /dev/null
 	gprof a.out > $<.gprof
diff --git a/inflate.c b/inflate.c
@@ -1,5 +1,4 @@
 #include <stdlib.h>
-#include <string.h>
 
 typedef unsigned char uchar;
 typedef unsigned short ushort;
@@ -197,6 +196,10 @@ static int build_huff(Huff *huff, uchar *lens, uint n, uint nbits) {
 		table[code].sym = i << 1;
 		code = revinc(code, nbits);
 	}
+/*
+for (i = 0; i < CodeBits - nbits - 1; i++)
+	count[i] = count[i + nbits + 1];
+*/
 	return 0;
 }
 
@@ -239,6 +242,46 @@ static uint getbits(State *s, int n) {
 	return k;
 }
 
+/* decode symbol bitwise if code is longer than huffbits */
+static uint decode_symbol_long(State *s, Huff *huff, uint bits, uint nbits, int cur) {
+	int sum = huff->sum;
+	uint huffbits = huff->nbits;
+	ushort *count = huff->count + huffbits + 1;
+
+	/* get bits if we are near the end */
+	if (s->src + 2 >= s->srcend) {
+		while (nbits < CodeBits - 1 && s->src < s->srcend) {
+			bits |= *s->src++ << nbits;
+			nbits += 8;
+		}
+		s->bits = bits;
+		s->nbits = nbits;
+	}
+	bits >>= huffbits;
+	nbits -= huffbits;
+	for (;;) {
+		if (!nbits--) {
+			if (s->src == s->srcend)
+				return FlateNeedInput;
+			bits = *s->src++;
+			nbits = 7;
+		}
+		cur |= bits & 1;
+		bits >>= 1;
+		sum += *count;
+		cur -= *count;
+		if (cur < 0)
+			break;
+		cur <<= 1;
+		count++;
+		if (count == huff->count + CodeBits)
+			return FlateError;
+	}
+	s->bits = bits;
+	s->nbits = nbits;
+	return huff->symbol[sum + cur];
+}
+
 /* decode a symbol from stream with huff code */
 static uint decode_symbol(State *s, Huff *huff) {
 	uint huffbits = huff->nbits;
@@ -282,51 +325,9 @@ static uint decode_symbol(State *s, Huff *huff) {
 		return entry.sym;
 	} else if (entry.len == 0)
 		return FlateError;
-	/* code is longer than huffbits: bitwise decode the rest */
-	{
-		int cur = entry.sym;
-		int sum = huff->sum;
-		/* TODO: count[0..huffbits] is never needed */
-		ushort *count = huff->count + huffbits + 1;
-		int needinput = 0;
-
-		/* save bits if we are near the end */
-		if (s->src + 2 >= s->srcend) {
-			while (nbits < CodeBits - 1 && s->src < s->srcend) {
-				bits |= *s->src++ << nbits;
-				nbits += 8;
-			}
-			s->bits = bits;
-			s->nbits = nbits;
-			needinput = 1;
-		}
-		bits >>= huffbits;
-		nbits -= huffbits;
-		for (;;) {
-			if (!nbits--) {
-				if (needinput)
-					return FlateNeedInput;
-				bits = *s->src++;
-				nbits = 7;
-			}
-			cur |= bits & 1;
-			bits >>= 1;
-			sum += *count;
-			cur -= *count;
-			if (cur < 0)
-				break;
-			cur <<= 1;
-			count++;
-			if (count == huff->count + CodeBits)
-				return FlateError;
-		}
-		s->bits = bits;
-		s->nbits = nbits;
-		return huff->symbol[sum + cur];
-	}
+	return decode_symbol_long(s, huff, bits, nbits, entry.sym);
 }
 
-
 /* decode a block of data from stream with trees */
 static int decode_block(State *s, Huff *lhuff, Huff *dhuff) {
 	uchar *win = s->win;