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Code Issues Releases Activity

improve CRC API

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- don't export any global var
 - provide either generated or hardcoded tables

Originally committed as revision 11409 to svn://svn.ffmpeg.org/ffmpeg/trunk
This commit is contained in:
Aurelien Jacobs
2008-01-04 23:09:58 +00:00
parent 83a0d3878c
commit 3abe5fbdc4
12 changed files with 279 additions and 55 deletions
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55
libavutil/crc.c
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@@ -21,16 +21,21 @@
#include "common.h"
#include "crc.h"
#if LIBAVUTIL_VERSION_INT < (50<<16)
AVCRC *av_crcEDB88320;
AVCRC *av_crc04C11DB7;
AVCRC *av_crc8005 ;
AVCRC *av_crc07 ;
#ifdef CONFIG_HARDCODED_TABLES
#include "crc_data.h"
#else
AVCRC av_crcEDB88320[257];
AVCRC av_crc04C11DB7[257];
AVCRC av_crc8005 [257];
AVCRC av_crc07 [257];
static struct {
uint8_t le;
uint8_t bits;
uint32_t poly;
} av_crc_table_params[AV_CRC_MAX] = {
[AV_CRC_8_ATM] = { 0, 8, 0x07 },
[AV_CRC_16_ANSI] = { 0, 16, 0x8005 },
[AV_CRC_16_CCITT] = { 0, 16, 0x1021 },
[AV_CRC_32_IEEE] = { 0, 32, 0x04C11DB7 },
[AV_CRC_32_IEEE_LE] = { 1, 32, 0xEDB88320 },
};
static AVCRC av_crc_table[AV_CRC_MAX][257];
#endif
/**
@@ -79,6 +84,24 @@ int av_crc_init(AVCRC *ctx, int le, int bits, uint32_t poly, int ctx_size){
return 0;
}
/**
* Get an initialized standard CRC table.
* @param crc_id ID of a standard CRC
* @return a pointer to the CRC table or NULL on failure
*/
const AVCRC *av_crc_get_table(AVCRCId crc_id){
#ifndef CONFIG_HARDCODED_TABLES
if (!av_crc_table[crc_id][sizeof(av_crc_table[crc_id])-1])
if (av_crc_init(av_crc_table[crc_id],
av_crc_table_params[crc_id].le,
av_crc_table_params[crc_id].bits,
av_crc_table_params[crc_id].poly,
sizeof(av_crc_table[crc_id])) < 0)
return NULL;
#endif
return av_crc_table[crc_id];
}
/**
* Calculate the CRC of a block
* @param crc CRC of previous blocks if any or initial value for CRC.
@@ -110,18 +133,18 @@ uint32_t av_crc(const AVCRC *ctx, uint32_t crc, const uint8_t *buffer, size_t le
main(void){
uint8_t buf[1999];
int i;
int p[4][4]={{1, 32, AV_CRC_32_IEEE_LE, 0x3D5CDD04},
{0, 32, AV_CRC_32_IEEE , 0xC0F5BAE0},
{0, 16, AV_CRC_16 , 0x1FBB },
{0, 8, AV_CRC_8_ATM , 0xE3 },};
AVCRC ctx[1 ? 1024:257];
int p[4][3]={{AV_CRC_32_IEEE_LE, 0xEDB88320, 0x3D5CDD04},
{AV_CRC_32_IEEE , 0x04C11DB7, 0xC0F5BAE0},
{AV_CRC_16_ANSI , 0x8005, 0x1FBB },
{AV_CRC_8_ATM , 0x07, 0xE3 },};
const AVCRC *ctx;
for(i=0; i<sizeof(buf); i++)
buf[i]= i+i*i;
for(i=0; i<4; i++){
av_crc_init(ctx, p[i][0], p[i][1], p[i][2], sizeof(ctx));
printf("crc %08X =%X\n", p[i][2], av_crc(ctx, 0, buf, sizeof(buf)));
ctx = av_crc_get_table(p[i][0]);
printf("crc %08X =%X\n", p[i][1], av_crc(ctx, 0, buf, sizeof(buf)));
}
}
#endif