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00021 #include "common.h"
00022 #include "crc.h"
00023
00024 #ifdef CONFIG_HARDCODED_TABLES
00025 #include "crc_data.h"
00026 #else
00027 static struct {
00028 uint8_t le;
00029 uint8_t bits;
00030 uint32_t poly;
00031 } av_crc_table_params[AV_CRC_MAX] = {
00032 [AV_CRC_8_ATM] = { 0, 8, 0x07 },
00033 [AV_CRC_16_ANSI] = { 0, 16, 0x8005 },
00034 [AV_CRC_16_CCITT] = { 0, 16, 0x1021 },
00035 [AV_CRC_32_IEEE] = { 0, 32, 0x04C11DB7 },
00036 [AV_CRC_32_IEEE_LE] = { 1, 32, 0xEDB88320 },
00037 };
00038 static AVCRC av_crc_table[AV_CRC_MAX][257];
00039 #endif
00040
00056 int av_crc_init(AVCRC *ctx, int le, int bits, uint32_t poly, int ctx_size){
00057 int i, j;
00058 uint32_t c;
00059
00060 if (bits < 8 || bits > 32 || poly >= (1LL<<bits))
00061 return -1;
00062 if (ctx_size != sizeof(AVCRC)*257 && ctx_size != sizeof(AVCRC)*1024)
00063 return -1;
00064
00065 for (i = 0; i < 256; i++) {
00066 if (le) {
00067 for (c = i, j = 0; j < 8; j++)
00068 c = (c>>1)^(poly & (-(c&1)));
00069 ctx[i] = c;
00070 } else {
00071 for (c = i << 24, j = 0; j < 8; j++)
00072 c = (c<<1) ^ ((poly<<(32-bits)) & (((int32_t)c)>>31) );
00073 ctx[i] = bswap_32(c);
00074 }
00075 }
00076 ctx[256]=1;
00077 #ifndef CONFIG_SMALL
00078 if(ctx_size >= sizeof(AVCRC)*1024)
00079 for (i = 0; i < 256; i++)
00080 for(j=0; j<3; j++)
00081 ctx[256*(j+1) + i]= (ctx[256*j + i]>>8) ^ ctx[ ctx[256*j + i]&0xFF ];
00082 #endif
00083
00084 return 0;
00085 }
00086
00092 const AVCRC *av_crc_get_table(AVCRCId crc_id){
00093 #ifndef CONFIG_HARDCODED_TABLES
00094 if (!av_crc_table[crc_id][sizeof(av_crc_table[crc_id])/sizeof(av_crc_table[crc_id][0])-1])
00095 if (av_crc_init(av_crc_table[crc_id],
00096 av_crc_table_params[crc_id].le,
00097 av_crc_table_params[crc_id].bits,
00098 av_crc_table_params[crc_id].poly,
00099 sizeof(av_crc_table[crc_id])) < 0)
00100 return NULL;
00101 #endif
00102 return av_crc_table[crc_id];
00103 }
00104
00112 uint32_t av_crc(const AVCRC *ctx, uint32_t crc, const uint8_t *buffer, size_t length){
00113 const uint8_t *end= buffer+length;
00114
00115 #ifndef CONFIG_SMALL
00116 if(!ctx[256])
00117 while(buffer<end-3){
00118 crc ^= le2me_32(*(const uint32_t*)buffer); buffer+=4;
00119 crc = ctx[3*256 + ( crc &0xFF)]
00120 ^ctx[2*256 + ((crc>>8 )&0xFF)]
00121 ^ctx[1*256 + ((crc>>16)&0xFF)]
00122 ^ctx[0*256 + ((crc>>24) )];
00123 }
00124 #endif
00125 while(buffer<end)
00126 crc = ctx[((uint8_t)crc) ^ *buffer++] ^ (crc >> 8);
00127
00128 return crc;
00129 }
00130
00131 #ifdef TEST
00132 #undef printf
00133 int main(void){
00134 uint8_t buf[1999];
00135 int i;
00136 int p[4][3]={{AV_CRC_32_IEEE_LE, 0xEDB88320, 0x3D5CDD04},
00137 {AV_CRC_32_IEEE , 0x04C11DB7, 0xC0F5BAE0},
00138 {AV_CRC_16_ANSI , 0x8005, 0x1FBB },
00139 {AV_CRC_8_ATM , 0x07, 0xE3 },};
00140 const AVCRC *ctx;
00141
00142 for(i=0; i<sizeof(buf); i++)
00143 buf[i]= i+i*i;
00144
00145 for(i=0; i<4; i++){
00146 ctx = av_crc_get_table(p[i][0]);
00147 printf("crc %08X =%X\n", p[i][1], av_crc(ctx, 0, buf, sizeof(buf)));
00148 }
00149 return 0;
00150 }
00151 #endif