Libav 0.7.1
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00001 /* 00002 * copyright (c) 2006 Michael Niedermayer <michaelni@gmx.at> 00003 * 00004 * This file is part of Libav. 00005 * 00006 * Libav is free software; you can redistribute it and/or 00007 * modify it under the terms of the GNU Lesser General Public 00008 * License as published by the Free Software Foundation; either 00009 * version 2.1 of the License, or (at your option) any later version. 00010 * 00011 * Libav is distributed in the hope that it will be useful, 00012 * but WITHOUT ANY WARRANTY; without even the implied warranty of 00013 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU 00014 * Lesser General Public License for more details. 00015 * 00016 * You should have received a copy of the GNU Lesser General Public 00017 * License along with Libav; if not, write to the Free Software 00018 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA 00019 */ 00020 00021 #include "config.h" 00022 #include "common.h" 00023 #include "bswap.h" 00024 #include "crc.h" 00025 00026 #if CONFIG_HARDCODED_TABLES 00027 #include "crc_data.h" 00028 #else 00029 static struct { 00030 uint8_t le; 00031 uint8_t bits; 00032 uint32_t poly; 00033 } av_crc_table_params[AV_CRC_MAX] = { 00034 [AV_CRC_8_ATM] = { 0, 8, 0x07 }, 00035 [AV_CRC_16_ANSI] = { 0, 16, 0x8005 }, 00036 [AV_CRC_16_CCITT] = { 0, 16, 0x1021 }, 00037 [AV_CRC_32_IEEE] = { 0, 32, 0x04C11DB7 }, 00038 [AV_CRC_32_IEEE_LE] = { 1, 32, 0xEDB88320 }, 00039 }; 00040 static AVCRC av_crc_table[AV_CRC_MAX][257]; 00041 #endif 00042 00059 int av_crc_init(AVCRC *ctx, int le, int bits, uint32_t poly, int ctx_size){ 00060 unsigned i, j; 00061 uint32_t c; 00062 00063 if (bits < 8 || bits > 32 || poly >= (1LL<<bits)) 00064 return -1; 00065 if (ctx_size != sizeof(AVCRC)*257 && ctx_size != sizeof(AVCRC)*1024) 00066 return -1; 00067 00068 for (i = 0; i < 256; i++) { 00069 if (le) { 00070 for (c = i, j = 0; j < 8; j++) 00071 c = (c>>1)^(poly & (-(c&1))); 00072 ctx[i] = c; 00073 } else { 00074 for (c = i << 24, j = 0; j < 8; j++) 00075 c = (c<<1) ^ ((poly<<(32-bits)) & (((int32_t)c)>>31) ); 00076 ctx[i] = av_bswap32(c); 00077 } 00078 } 00079 ctx[256]=1; 00080 #if !CONFIG_SMALL 00081 if(ctx_size >= sizeof(AVCRC)*1024) 00082 for (i = 0; i < 256; i++) 00083 for(j=0; j<3; j++) 00084 ctx[256*(j+1) + i]= (ctx[256*j + i]>>8) ^ ctx[ ctx[256*j + i]&0xFF ]; 00085 #endif 00086 00087 return 0; 00088 } 00089 00095 const AVCRC *av_crc_get_table(AVCRCId crc_id){ 00096 #if !CONFIG_HARDCODED_TABLES 00097 if (!av_crc_table[crc_id][FF_ARRAY_ELEMS(av_crc_table[crc_id])-1]) 00098 if (av_crc_init(av_crc_table[crc_id], 00099 av_crc_table_params[crc_id].le, 00100 av_crc_table_params[crc_id].bits, 00101 av_crc_table_params[crc_id].poly, 00102 sizeof(av_crc_table[crc_id])) < 0) 00103 return NULL; 00104 #endif 00105 return av_crc_table[crc_id]; 00106 } 00107 00115 uint32_t av_crc(const AVCRC *ctx, uint32_t crc, const uint8_t *buffer, size_t length){ 00116 const uint8_t *end= buffer+length; 00117 00118 #if !CONFIG_SMALL 00119 if(!ctx[256]) { 00120 while(((intptr_t) buffer & 3) && buffer < end) 00121 crc = ctx[((uint8_t)crc) ^ *buffer++] ^ (crc >> 8); 00122 00123 while(buffer<end-3){ 00124 crc ^= av_le2ne32(*(const uint32_t*)buffer); buffer+=4; 00125 crc = ctx[3*256 + ( crc &0xFF)] 00126 ^ctx[2*256 + ((crc>>8 )&0xFF)] 00127 ^ctx[1*256 + ((crc>>16)&0xFF)] 00128 ^ctx[0*256 + ((crc>>24) )]; 00129 } 00130 } 00131 #endif 00132 while(buffer<end) 00133 crc = ctx[((uint8_t)crc) ^ *buffer++] ^ (crc >> 8); 00134 00135 return crc; 00136 } 00137 00138 #ifdef TEST 00139 #undef printf 00140 int main(void){ 00141 uint8_t buf[1999]; 00142 int i; 00143 int p[4][3]={{AV_CRC_32_IEEE_LE, 0xEDB88320, 0x3D5CDD04}, 00144 {AV_CRC_32_IEEE , 0x04C11DB7, 0xC0F5BAE0}, 00145 {AV_CRC_16_ANSI , 0x8005, 0x1FBB }, 00146 {AV_CRC_8_ATM , 0x07, 0xE3 },}; 00147 const AVCRC *ctx; 00148 00149 for(i=0; i<sizeof(buf); i++) 00150 buf[i]= i+i*i; 00151 00152 for(i=0; i<4; i++){ 00153 ctx = av_crc_get_table(p[i][0]); 00154 printf("crc %08X =%X\n", p[i][1], av_crc(ctx, 0, buf, sizeof(buf))); 00155 } 00156 return 0; 00157 } 00158 #endif