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Diffstat (limited to 'contrib/ffmpeg/libavutil/crc.c')
| -rw-r--r-- | contrib/ffmpeg/libavutil/crc.c | 151 |
1 files changed, 151 insertions, 0 deletions
diff --git a/contrib/ffmpeg/libavutil/crc.c b/contrib/ffmpeg/libavutil/crc.c new file mode 100644 index 000000000..743a64038 --- /dev/null +++ b/contrib/ffmpeg/libavutil/crc.c @@ -0,0 +1,151 @@ +/* + * 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 "common.h" +#include "crc.h" + +#ifdef 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 + +/** + * Inits a crc table. + * @param ctx must be an array of sizeof(AVCRC)*257 or sizeof(AVCRC)*1024 + * @param cts_size size of ctx in bytes + * @param le if 1, lowest bit represents coefficient for highest exponent + * of 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; +#ifndef 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; +} + +/** + * 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])/sizeof(av_crc_table[crc_id][0])-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. + * @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; + +#ifndef CONFIG_SMALL + if(!ctx[256]) + 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 |