inflate: cleanup CRC calculation
Move CRC calculation into inflate code
Cleanup table calculation code
Signed-off-by: Matt Mackall <[email protected]>
Index: 2.6.16-rc4-inflate/lib/inflate.c
===================================================================
--- 2.6.16-rc4-inflate.orig/lib/inflate.c 2006-02-22 17:16:08.000000000 -0600
+++ 2.6.16-rc4-inflate/lib/inflate.c 2006-02-22 17:16:10.000000000 -0600
@@ -109,6 +109,10 @@
#include <asm/types.h>
+static u32 crc_32_tab[256];
+static u32 crc; /* dummy var until users get cleaned up */
+#define CRCPOLY_LE 0xedb88320
+
/* Huffman code lookup table entry--this entry is four bytes for machines
that have 16-bit pointers (e.g. PC's in the small or medium model).
Valid extra bits are 0..13. e == 15 is EOB (end of block), e == 16
@@ -128,7 +132,7 @@ struct huft {
struct iostate {
u8 *window;
int opos, osize, bits;
- u32 buf;
+ u32 buf, crc;
};
/* Function prototypes */
@@ -154,6 +158,12 @@ static int INIT inflate(struct iostate *
static void flush_output(struct iostate *io)
{
+ int i;
+
+ for (i = 0; i < io->opos; i++)
+ io->crc = crc_32_tab[(io->window[i] ^ (int)io->crc) & 0xff]
+ ^ (io->crc >> 8);
+
outcnt = io->opos;
flush_window();
io->opos = 0;
@@ -906,47 +916,16 @@ static int INIT inflate(struct iostate *
*
**********************************************************************/
-static u32 crc_32_tab[256];
-static u32 crc; /* initialized in makecrc() so it'll reside in bss */
-#define CRC_VALUE (crc ^ 0xffffffffUL)
-
-/*
- * Code to compute the CRC-32 table. Borrowed from
- * gzip-1.0.3/makecrc.c.
- * Not copyrighted 1990 Mark Adler
- */
-
static void INIT makecrc(void)
{
+ unsigned i, j;
+ u32 c = 1;
- unsigned long c; /* crc shift register */
- unsigned long e; /* polynomial exclusive-or pattern */
- int i; /* counter for all possible eight bit values */
- int k; /* byte being shifted into crc apparatus */
-
- /* terms of polynomial defining this crc (except x^32): */
- static const int p[] =
- { 0, 1, 2, 4, 5, 7, 8, 10, 11, 12, 16, 22, 23, 26 };
-
- /* Make exclusive-or pattern from polynomial */
- e = 0;
- for (i = 0; i < sizeof(p) / sizeof(int); i++)
- e |= 1L << (31 - p[i]);
-
- crc_32_tab[0] = 0;
-
- for (i = 1; i < 256; i++) {
- c = 0;
- for (k = i | 256; k != 1; k >>= 1) {
- c = c & 1 ? (c >> 1) ^ e : c >> 1;
- if (k & 1)
- c ^= e;
- }
- crc_32_tab[i] = c;
+ for (i = 128; i; i >>= 1) {
+ c = (c >> 1) ^ ((c & 1) ? CRCPOLY_LE : 0);
+ for (j = 0; j < 256; j += 2 * i)
+ crc_32_tab[i + j] = c ^ crc_32_tab[j];
}
-
- /* this is initialized here so this code could reside in ROM */
- crc = 0xffffffffUL; /* shift register contents */
}
/* gzip flag byte */
@@ -966,14 +945,15 @@ static int INIT gunzip(void)
u8 flags;
unsigned char magic[2]; /* magic header */
char method;
- u32 orig_crc = 0; /* original crc */
- u32 orig_len = 0; /* original uncompressed length */
+ u32 orig_crc;
+ u32 orig_len;
int res;
struct iostate io;
io.window = window;
io.osize = WSIZE;
io.opos = io.bits = io.buf = 0;
+ io.crc = 0xffffffffUL;
magic[0] = get_byte();
magic[1] = get_byte();
@@ -1051,8 +1031,7 @@ static int INIT gunzip(void)
return -1;
}
- /* Get the crc and original length */
- /* crc32 (see algorithm.doc)
+ /* Get the crc and original length
* uncompressed input size modulo 2^32
*/
orig_crc = (u32)get_byte();
@@ -1066,7 +1045,7 @@ static int INIT gunzip(void)
orig_len |= (u32)get_byte() << 24;
/* Validate decompression */
- if (orig_crc != CRC_VALUE) {
+ if (orig_crc != ~io.crc) {
error("crc error");
return -1;
}
-
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