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/*
* copyright (c) 2006 Michael Niedermayer <michaelni@gmx.at>
*
* This file is part of FFmpeg.
*
* FFmpeg is free software; you can redistribute it and/or
* modify it under the terms of the GNU Lesser General Public
* License as published by the Free Software Foundation; either
* version 2.1 of the License, or (at your option) any later version.
*
* FFmpeg is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
* Lesser General Public License for more details.
*
* You should have received a copy of the GNU Lesser General Public
* License along with FFmpeg; if not, write to the Free Software
* Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
*/
#include "config.h"
#include "bswap.h"
#include "crc.h"
#if CONFIG_HARDCODED_TABLES
#include "crc_data.h"
#else
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
/**
* Initializes a CRC table.
* @param ctx must be an array of size sizeof(AVCRC)*257 or sizeof(AVCRC)*1024
* @param cts_size size of ctx in bytes
* @param le If 1, the lowest bit represents the coefficient for the highest
* exponent of the corresponding polynomial (both for poly and
* actual CRC).
* If 0, you must swap the CRC parameter and the result of av_crc
* if you need the standard representation (can be simplified in
* most cases to e.g. bswap16):
* bswap_32(crc << (32-bits))
* @param bits number of bits for the CRC
* @param poly generator polynomial without the x**bits coefficient, in the
* representation as specified by le
* @return <0 on failure
*/
int av_crc_init(AVCRC *ctx, int le, int bits, uint32_t poly, int ctx_size){
int i, j;
uint32_t c;
if (bits < 8 || bits > 32 || poly >= (1LL<<bits))
return -1;
if (ctx_size != sizeof(AVCRC)*257 && ctx_size != sizeof(AVCRC)*1024)
return -1;
for (i = 0; i < 256; i++) {
if (le) {
for (c = i, j = 0; j < 8; j++)
c = (c>>1)^(poly & (-(c&1)));
ctx[i] = c;
} else {
for (c = i << 24, j = 0; j < 8; j++)
c = (c<<1) ^ ((poly<<(32-bits)) & (((int32_t)c)>>31) );
ctx[i] = bswap_32(c);
}
}
ctx[256]=1;
#if !CONFIG_SMALL
if(ctx_size >= sizeof(AVCRC)*1024)
for (i = 0; i < 256; i++)
for(j=0; j<3; j++)
ctx[256*(j+1) + i]= (ctx[256*j + i]>>8) ^ ctx[ ctx[256*j + i]&0xFF ];
#endif
return 0;
}
/**
* Gets 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){
#if !CONFIG_HARDCODED_TABLES
if (!av_crc_table[crc_id][FF_ARRAY_ELEMS(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];
}
/**
* Calculates the CRC of a block.
* @param crc CRC of previous blocks if any or initial value for CRC
* @return CRC updated with the data from the given block
*
* @see av_crc_init() "le" parameter
*/
uint32_t av_crc(const AVCRC *ctx, uint32_t crc, const uint8_t *buffer, size_t length){
const uint8_t *end= buffer+length;
#if !CONFIG_SMALL
if(!ctx[256]) {
while(((intptr_t) buffer & 3) && buffer < end)
crc = ctx[((uint8_t)crc) ^ *buffer++] ^ (crc >> 8);
while(buffer<end-3){
crc ^= le2me_32(*(const uint32_t*)buffer); buffer+=4;
crc = ctx[3*256 + ( crc &0xFF)]
^ctx[2*256 + ((crc>>8 )&0xFF)]
^ctx[1*256 + ((crc>>16)&0xFF)]
^ctx[0*256 + ((crc>>24) )];
}
}
#endif
while(buffer<end)
crc = ctx[((uint8_t)crc) ^ *buffer++] ^ (crc >> 8);
return crc;
}
#ifdef TEST
#undef printf
int main(void){
uint8_t buf[1999];
int i;
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++){
ctx = av_crc_get_table(p[i][0]);
printf("crc %08X =%X\n", p[i][1], av_crc(ctx, 0, buf, sizeof(buf)));
}
return 0;
}
#endif
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