crc.rar_CRC 半字节_半字节查表

/****************************************/ /* Copyright (c) 2004, 通信工程学院戴佳 */ /* All rights reserved. */ /* 作 者：戴佳 */ /****************************************/ #include "CRC.h" /* 按位求CRC */ uint bit_crc(uchar *ptr, uchar len) { uchar i; uint crc = 0; while (len--!=0) { for (i=0x80; i!=0; i/=2) { if ((crc&0x8000)!=0) { crc*=2; // 余式CRC乘以2 crc^=0x11021; // 再求CRC } else crc*=2; if ((*ptr&i)!=0) crc^=0x11021; // 再加上本位的CRC } ptr++; } return(crc); } /* 按字节查表求CRC */ uint byte_crc(uchar *ptr, uchar len) { uint crc; uchar da; /* CRC 余式表 */ uint xdata crc_ta[256]= { 0x0000, 0x1021, 0x2042, 0x3063, 0x4084, 0x50a5, 0x60c6, 0x70e7, 0x8108, 0x9129, 0xa14a, 0xb16b, 0xc18c, 0xd1ad, 0xe1ce, 0xf1ef, 0x1231, 0x0210, 0x3273, 0x2252, 0x52b5, 0x4294, 0x72f7, 0x62d6, 0x9339, 0x8318, 0xb37b, 0xa35a, 0xd3bd, 0xc39c, 0xf3ff, 0xe3de, 0x2462, 0x3443, 0x0420, 0x1401, 0x64e6, 0x74c7, 0x44a4, 0x5485, 0xa56a, 0xb54b, 0x8528, 0x9509, 0xe5ee, 0xf5cf, 0xc5ac, 0xd58d, 0x3653, 0x2672, 0x1611, 0x0630, 0x76d7, 0x66f6, 0x5695, 0x46b4, 0xb75b, 0xa77a, 0x9719, 0x8738, 0xf7df, 0xe7fe, 0xd79d, 0xc7bc, 0x48c4, 0x58e5, 0x6886, 0x78a7, 0x0840, 0x1861, 0x2802, 0x3823, 0xc9cc, 0xd9ed, 0xe98e, 0xf9af, 0x8948, 0x9969, 0xa90a, 0xb92b, 0x5af5, 0x4ad4, 0x7ab7, 0x6a96, 0x1a71, 0x0a50, 0x3a33, 0x2a12, 0xdbfd, 0xcbdc, 0xfbbf, 0xeb9e, 0x9b79, 0x8b58, 0xbb3b, 0xab1a, 0x6ca6, 0x7c87, 0x4ce4, 0x5cc5, 0x2c22, 0x3c03, 0x0c60, 0x1c41, 0xedae, 0xfd8f, 0xcdec, 0xddcd, 0xad2a, 0xbd0b, 0x8d68, 0x9d49, 0x7e97, 0x6eb6, 0x5ed5, 0x4ef4, 0x3e13, 0x2e32, 0x1e51, 0x0e70, 0xff9f, 0xefbe, 0xdfdd, 0xcffc, 0xbf1b, 0xaf3a, 0x9f59, 0x8f78, 0x9188, 0x81a9, 0xb1ca, 0xa1eb, 0xd10c, 0xc12d, 0xf14e, 0xe16f, 0x1080, 0x00a1, 0x30c2, 0x20e3, 0x5004, 0x4025, 0x7046, 0x6067, 0x83b9, 0x9398, 0xa3fb, 0xb3da, 0xc33d, 0xd31c, 0xe37f, 0xf35e, 0x02b1, 0x1290, 0x22f3, 0x32d2, 0x4235, 0x5214, 0x6277, 0x7256, 0xb5ea, 0xa5cb, 0x95a8, 0x8589, 0xf56e, 0xe54f, 0xd52c, 0xc50d, 0x34e2, 0x24c3, 0x14a0, 0x0481, 0x7466, 0x6447, 0x5424, 0x4405, 0xa7db, 0xb7fa, 0x8799, 0x97b8, 0xe75f, 0xf77e, 0xc71d, 0xd73c, 0x26d3, 0x36f2, 0x0691, 0x16b0, 0x6657, 0x7676, 0x4615, 0x5634, 0xd94c, 0xc96d, 0xf90e, 0xe92f, 0x99c8, 0x89e9, 0xb98a, 0xa9ab, 0x5844, 0x4865, 0x7806, 0x6827, 0x18c0, 0x08e1, 0x3882, 0x28a3, 0xcb7d, 0xdb5c, 0xeb3f, 0xfb1e, 0x8bf9, 0x9bd8, 0xabbb, 0xbb9a, 0x4a75, 0x5a54, 0x6a37, 0x7a16, 0x0af1, 0x1ad0, 0x2ab3, 0x3a92, 0xfd2e, 0xed0f, 0xdd6c, 0xcd4d, 0xbdaa, 0xad8b, 0x9de8, 0x8dc9, 0x7c26, 0x6c07, 0x5c64, 0x4c45, 0x3ca2, 0x2c83, 0x1ce0, 0x0cc1, 0xef1f, 0xff3e, 0xcf5d, 0xdf7c, 0xaf9b, 0xbfba, 0x8fd9, 0x9ff8, 0x6e17, 0x7e36, 0x4e55, 0x5e74, 0x2e93, 0x3eb2, 0x0ed1, 0x1ef0 }; crc = 0; while(len--!=0) { da=(uchar) (crc/256); // 以8位二进制数的形式暂存CRC的高8位 crc<<=8; // 左移8位，相当于CRC的低8位乘以2的8次方 crc^=crc_ta[da^*ptr]; // 高8位和当前字节相加后再查表求CRC，再加上以前的CRC ptr++; } return(crc); } /* 按半字节查表求CRC */ uint halfbyte_crc(uchar *ptr, uchar len) { uint crc; uchar da; /* CRC余式表 */ uint xdata crc_ta[16]= { 0x0000,0x1021,0x2042,0x3063,0x4084,0x50a5,0x60c6,0x70e7, 0x8108,0x9129,0xa14a,0xb16b,0xc18c,0xd1ad,0xe1ce,0xf1ef }; crc = 0; while(len--!=0) { da=((uchar)(crc/256))/16; // 暂存CRC的高四位 crc<<=4; // CRC右移4位，相当于取CRC的低12位 crc^=crc_ta[da^(*ptr/16)]; // CRC的高4位和本字节的前半字节相加后查表 计算CRC，然后加上上一次CRC的余数 */ da=((uchar)(crc/256))/16; // 暂存CRC的高4位 crc<<=4; // CRC右移4位，相当于CRC的低12位 crc^=crc_ta[da^(*ptr&0x0f)]; /* CRC的高4位和本字节的后半字节相加后查表 计算CRC，然后再加上上一次CRC的余数 */ ptr++; } return(crc); } /* 主程序 */ void main() { uchar len; uint crc_bit; uint crc_byte; uint crc_halfbyte; len = 8; crc_bit = bit_crc(testdata,len); // 调用按位求CRC子函数 crc_byte = byte_crc(testdata,len); // 调用按字节查表求CRC子函数 crc_halfbyte = halfbyte_crc(testdata,len); // 调用按半字节查表求CRC子函数 while(1); }