2 * copyright (c) 2006 Michael Niedermayer <michaelni@gmx.at>
4 * This file is part of FFmpeg.
6 * FFmpeg is free software; you can redistribute it and/or
7 * modify it under the terms of the GNU Lesser General Public
8 * License as published by the Free Software Foundation; either
9 * version 2.1 of the License, or (at your option) any later version.
11 * FFmpeg is distributed in the hope that it will be useful,
12 * but WITHOUT ANY WARRANTY; without even the implied warranty of
13 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
14 * Lesser General Public License for more details.
16 * You should have received a copy of the GNU Lesser General Public
17 * License along with FFmpeg; if not, write to the Free Software
18 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
24 #if LIBAVUTIL_VERSION_INT < (50<<16)
25 AVCRC *av_crcEDB88320;
26 AVCRC *av_crc04C11DB7;
30 AVCRC av_crcEDB88320[257];
31 AVCRC av_crc04C11DB7[257];
32 AVCRC av_crc8005 [257];
38 * @param ctx must be an array of sizeof(AVCRC)*257 or sizeof(AVCRC)*1024
39 * @param cts_size size of ctx in bytes
40 * @param le if 1, lowest bit represents coefficient for highest exponent
41 * of corresponding polynomial (both for poly and actual CRC).
42 * If 0, you must swap the crc parameter and the result of av_crc
43 * if you need the standard representation (can be simplified in
44 * most cases to e.g. bswap16):
45 * bswap_32(crc << (32-bits))
46 * @param bits number of bits for the CRC
47 * @param poly generator polynomial without the x**bits coefficient, in the
48 * representation as specified by le
49 * @return <0 on failure
51 int av_crc_init(AVCRC *ctx, int le, int bits, uint32_t poly, int ctx_size){
55 if (bits < 8 || bits > 32 || poly >= (1LL<<bits))
57 if (ctx_size != sizeof(AVCRC)*257 && ctx_size != sizeof(AVCRC)*1024)
60 for (i = 0; i < 256; i++) {
62 for (c = i, j = 0; j < 8; j++)
63 c = (c>>1)^(poly & (-(c&1)));
66 for (c = i << 24, j = 0; j < 8; j++)
67 c = (c<<1) ^ ((poly<<(32-bits)) & (((int32_t)c)>>31) );
73 if(ctx_size >= sizeof(AVCRC)*1024)
74 for (i = 0; i < 256; i++)
76 ctx[256*(j+1) + i]= (ctx[256*j + i]>>8) ^ ctx[ ctx[256*j + i]&0xFF ];
83 * Calculate the CRC of a block
84 * @param crc CRC of previous blocks if any or initial value for CRC.
85 * @return CRC updated with the data from the given block
87 * @see av_crc_init() "le" parameter
89 uint32_t av_crc(const AVCRC *ctx, uint32_t crc, const uint8_t *buffer, size_t length){
90 const uint8_t *end= buffer+length;
95 crc ^= le2me_32(*(uint32_t*)buffer); buffer+=4;
96 crc = ctx[3*256 + ( crc &0xFF)]
97 ^ctx[2*256 + ((crc>>8 )&0xFF)]
98 ^ctx[1*256 + ((crc>>16)&0xFF)]
99 ^ctx[0*256 + ((crc>>24) )];
103 crc = ctx[((uint8_t)crc) ^ *buffer++] ^ (crc >> 8);
113 int p[4][4]={{1, 32, AV_CRC_32_IEEE_LE, 0x3D5CDD04},
114 {0, 32, AV_CRC_32_IEEE , 0xC0F5BAE0},
115 {0, 16, AV_CRC_16 , 0x1FBB },
116 {0, 8, AV_CRC_8_ATM , 0xE3 },};
117 AVCRC ctx[1 ? 1024:257];
119 for(i=0; i<sizeof(buf); i++)
123 av_crc_init(ctx, p[i][0], p[i][1], p[i][2], sizeof(ctx));
124 printf("crc %08X =%X\n", p[i][2], av_crc(ctx, 0, buf, sizeof(buf)));