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104 lines
3.0 KiB
104 lines
3.0 KiB
/* |
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* copyright (c) 2006 Michael Niedermayer <michaelni@gmx.at> |
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* |
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* This file is part of FFmpeg. |
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* |
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* FFmpeg is free software; you can redistribute it and/or |
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* modify it under the terms of the GNU Lesser General Public |
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* License as published by the Free Software Foundation; either |
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* version 2.1 of the License, or (at your option) any later version. |
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* |
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* FFmpeg is distributed in the hope that it will be useful, |
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* but WITHOUT ANY WARRANTY; without even the implied warranty of |
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU |
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* Lesser General Public License for more details. |
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* |
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* You should have received a copy of the GNU Lesser General Public |
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* License along with FFmpeg; if not, write to the Free Software |
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* Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA |
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*/ |
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#include "common.h" |
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#include "crc.h" |
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AVCRC *av_crcEDB88320; |
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AVCRC *av_crc04C11DB7; |
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AVCRC *av_crc8005 ; |
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AVCRC *av_crc07 ; |
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/** |
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* Inits a crc table. |
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* @param ctx must be an array of sizeof(AVCRC)*257 or sizeof(AVCRC)*1024 |
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* @param cts_size size of ctx in bytes |
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* @return <0 on failure |
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*/ |
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int av_crc_init(AVCRC *ctx, int le, int bits, uint32_t poly, int ctx_size){ |
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int i, j; |
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uint32_t c; |
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if (bits < 8 || bits > 32 || poly >= (1LL<<bits)) |
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return -1; |
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if (ctx_size != sizeof(AVCRC)*257 && ctx_size != sizeof(AVCRC)*1024) |
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return -1; |
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for (i = 0; i < 256; i++) { |
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if (le) { |
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for (c = i, j = 0; j < 8; j++) |
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c = (c>>1)^(poly & (-(c&1))); |
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ctx[i] = c; |
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} else { |
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for (c = i << 24, j = 0; j < 8; j++) |
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c = (c<<1) ^ ((poly<<(32-bits)) & (((int32_t)c)>>31) ); |
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ctx[i] = bswap_32(c); |
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} |
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} |
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ctx[256]=1; |
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#ifndef CONFIG_SMALL |
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if(ctx_size >= sizeof(AVCRC)*1024) |
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for (i = 0; i < 256; i++) |
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for(j=0; j<3; j++) |
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ctx[256*(j+1) + i]= (ctx[256*j + i]>>8) ^ ctx[ ctx[256*j + i]&0xFF ]; |
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#endif |
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return 0; |
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} |
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uint32_t av_crc(const AVCRC *ctx, uint32_t crc, const uint8_t *buffer, size_t length){ |
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const uint8_t *end= buffer+length; |
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#ifndef CONFIG_SMALL |
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if(!ctx[256]) |
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while(buffer<end-3){ |
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crc ^= le2me_32(*(uint32_t*)buffer); buffer+=4; |
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crc = ctx[3*256 + ( crc &0xFF)] |
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^ctx[2*256 + ((crc>>8 )&0xFF)] |
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^ctx[1*256 + ((crc>>16)&0xFF)] |
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^ctx[0*256 + ((crc>>24) )]; |
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} |
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#endif |
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while(buffer<end) |
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crc = ctx[((uint8_t)crc) ^ *buffer++] ^ (crc >> 8); |
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return crc; |
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} |
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#ifdef TEST |
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#undef printf |
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main(){ |
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uint8_t buf[1999]; |
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int i; |
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int p[4][4]={{1, 32, 0xedb88320L, 0x3D5CDD04}, |
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{0, 32, 0x04c11db7L, 0xC0F5BAE0}, |
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{0, 16, 0x8005 , 0x1FBB }, |
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{0, 8, 0x07 , 0xE3 },}; |
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AVCRC ctx[1 ? 1024:257]; |
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for(i=0; i<sizeof(buf); i++) |
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buf[i]= i+i*i; |
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for(i=0; i<4; i++){ |
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av_crc_init(ctx, p[i][0], p[i][1], p[i][2], sizeof(ctx)); |
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printf("crc %08X =%X\n", p[i][2], av_crc(ctx, 0, buf, sizeof(buf))); |
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} |
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} |
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#endif
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