求crc算法程序！
/* c header file : crc16.h */
#ifndef _crc16_h
#define _crc16_h
#include <limits.h>
#if USHRT_MAX == 0xFFFF
typedef unsigned short int uint16;
#elif UINT_MAX == 0xFFFF
typedef unsigned int uint16;
#else
#error define a 16 bit type
#endif
/* 0 -- 使用字节算法,使用一个256单元的常量表,速度快,占用RAM大.
* 1 -- 采用半字节算法,使用一个16单元的常量表,是速度和空间的折中.
* 其它 -- 采用位算法,速度慢,不需要常量表.
*/
#define CRC_CALC_MODE 1
#ifdef _cplusplus
extern \"C\"
{
#endif
/*
* 函数名称: crc16
* 功能: CRC-CCITT crc16 校验算法, 多项式0x11021(欧洲CCITT 推荐).
* ptr -- 待crc的数据数组,每一个中放的是8位的一个无符号整型
* 输入参数不检查ptr中的数组是否有效,请调用前保证有效.
* len -- 数组的长度
* 返回值 -- crc的结果,16位无符号整型
*/
uint16 crc16(const uint16 *ptr, uint16 len);
#ifdef _cplusplus
};
#endif
#endif /* _crc16_h */
/*end of file : crc16.h */
/* c source file : crc16.c */
#include \"crc16.h\"
#if CRC_CALC_MODE == 0
/* 按字节crc16, 0x11021(欧洲CCITT 推荐) */
uint16 crc16(const uint16 *ptr, uint16 len)
{
uint16 crc;
uint16 da;
const uint16 crc_tbl[256] =
{
/* CRC 余式表, 根据0x11021计算得到*/
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)
{
/* 以8位二进制数的形式暂存CRC 的高8位 */
da=(uint16)(crc/256);
/* 左移8位，相当于CRC 的低8 位乘以8^2 */
crc <<= 8;
/* 高8位和当前字节相加后再查表求CRC，再加上以前的CRC */
crc ^= crc_tbl[da^*ptr];
ptr++;
}
return (crc);
}
#elif CRC_CALC_MODE == 1
/* 按半字节crc16, 0x11021(欧洲CCITT 推荐) */
uint16 crc16(const uint16 *ptr, uint16 len)
{
uint16 crc;
uint16 da;
/* CRC 余式表, 根据 0x11021 计算得到*/
const uint16 crc_tbl[16] =
{
0x0000,0x1021,0x2042,0x3063,0x4084,0x50a5,0x60c6,0x70e7,
0x8108,0x9129,0xa14a,0xb16b,0xc18c,0xd1ad,0xe1ce,0xf1ef,
};
crc = 0;
while(len-- != 0)
{
/* 暂存CRC 的高四位 */
da = (uint16)(crc/256)/16;
crc <<= 4; /* CRC 右移4 位，相当于取CRC 的低12 位）*/
/* 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 */
crc ^= crc_tbl[da^(*ptr/16)];
da = ((uint16)(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 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 */
crc ^= crc_tbl[da^(*ptr&0x0f)];
ptr++;
}
return (crc);
}
#else
/* 按位crc16, 0x11021(欧洲 CCITT 推荐) */
uint16 crc16(const uint16 *ptr, uint16 len)
{
uint16 i;
uint16 crc=0;
while(len-- != 0)
{
for(i=0x80; i!=0; i/=2)
{
if((crc&0x8000) != 0)
{
crc *= 2;
crc ^= 0x1021;
}
else
crc *= 2; /* 余式 CRC 乘以 2 再求 CRC */
if((*ptr&i) != 0)
crc ^= 0x1021; /* 再加上本位的 CRC */
}
ptr++;
}
return (crc);
}
#endif
/* end of file : crc16.c */
/**********************************************************************
*
* Filename: main.c
*
* Description: A simple test program for the CRC implementations.
*
* Notes: To test a different CRC standard, modify crc.h.
*
*
* Copyright (c) 2000 by Michael Barr. This software is placed into
* the public domain and may be used for any purpose. However, this
* notice must not be changed or removed and no warranty is either
* expressed or implied by its publication or distribution.
**********************************************************************/
#include <stdio.h>
#include <string.h>
#include \"crc16.h\"
#ifdef _MSC_VER
void main(void)
{
unsigned int i;
#else
void do_crc(void)
{
#endif
uint16 crc_val=0;
uint16 test[128] =
{
0x77,0xd1,0xe6,0x61,0xea,0x6d,0x72,0x56,0x4e,0x91,
0x89,0xc8,0x61,0x9a,0x7f,0x13,0x50,0x92,0x1d,0xcf,
0xa2,0x62,0x55,0x88,0x9d,0xa1,0x1e,0xbb,0xa6,0x1c,
0xd2,0x89,0x45,0xb5,0x73,0x71,0xc2,0xb6,0x9a,0x34,
0x67,0x4c,0x13,0x4e,0xd9,0xef,0xe4,0xf3,0xe8,0xe2,
0x83,0xbe,0xe4,0x6d,0xcf,0x8f,0x08,0xc3,0xcf,0x24,
0x85,0xc4,0x5f,0x94,0x66,0x76,0xf6,0x06,0xaa,0xa7,
0x7b,0xca,0xe1,0xbf,0x8c,0x5d,0x3c,0xde,0x26,0xf1,
0xb9,0xfb,0x4c,0xe8,0x20,0x67,0x9b,0x2e,0xc6,0xb1,
0xc9,0x63,0x63,0x06,0x0d,0x4f,0xb0,0x22,0x30,0x2a,
0xaa,0x95,0x21,0xba,0x38,0x12,0x55,0x2d,0x32,0x8c,
0x0d,0x81,0x2d,0x75,0x90,0x12,0xb1,0x64,0xbd,0x27,
0x8a,0xa5,0xe4,0x8f,0xc1,0x6a,0xab,0xf5 //,0x33,0x4c
};
crc_val = crc_val;
crc_val = crc16(test, sizeof(test)/sizeof(uint16));
#ifdef _MSC_VER
//printf(\"The crc16() of \\\"%s\\\" is 0x%04X\\n\", test, crc_val);
printf(\"\\n\\ndata
128 bytes)\\n\"
;
for(i=0; i<128; i++)
{
if(i!=0 && i%10==0)
printf(\"\\n\"
;
printf(\"%02X\", test);
}
printf(\"\\n\\ncrc16:%02X\\n\\n\",crc_val);
#endif
} /* main() */
首先ygl_bj的详细解答,我觉的用查表法,效率比较高,但是我用的是美国标准的CRC-16算法,不知道那里可以找到表格下载呢!!
以下是CRC-16的查表算法,测试没有问题,提供给大家参考!!
unsigned int crc_tab[256]=
{ /* CRC-16余式表 根据0xa001得到的*/
0x0000,0xc0c1,0xc181,0x0140,0xc301,0x03c0,0x0280,0xc241,
0xc601,0x06c0,0x0780,0xc741,0x0500,0xc5c1,0xc481,0x0440,
0xcc01,0x0cc0,0x0d80,0xcd41,0x0f00,0xcfc1,0xce81,0x0e40,
0x0a00,0xcac1,0xcb81,0x0b40,0xc901,0x09c0,0x0880,0xc841,
0xd801,0x18c0,0x1980,0xd941,0x1b00,0xdbc1,0xda81,0x1a40,
0x1e00,0xdec1,0xdf81,0x1f40,0xdd01,0x1dc0,0x1c80,0xdc41,
0x1400,0xd4c1,0xd581,0x1540,0xd701,0x17c0,0x1680,0xd641,
0xd201,0x12c0,0x1380,0xd341,0x1100,0xd1c1,0xd081,0x1040,
0xf001,0x30c0,0x3180,0xf141,0x3300,0xf3c1,0xf281,0x3240,
0x3600,0xf6c1,0xf781,0x3740,0xf501,0x35c0,0x3480,0xf441,
0x3c00,0xfcc1,0xfd81,0x3d40,0xff01,0x3fc0,0x3e80,0xfe41,
0xfa01,0x3ac0,0x3b80,0xfb41,0x3900,0xf9c1,0xf881,0x3840,
0x2800,0xe8c1,0xe981,0x2940,0xeb01,0x2bc0,0x2a80,0xea41,
0xee01,0x2ec0,0x2f80,0xef41,0x2d00,0xedc1,0xec81,0x2c40,
0xe401,0x24c0,0x2580,0xe541,0x2700,0xe7c1,0xe681,0x2640,
0x2200,0xe2c1,0xe381,0x2340,0xe101,0x21c0,0x2080,0xe041,
0xa001,0x60c0,0x6180,0xa141,0x6300,0xa3c1,0xa281,0x6240,
0x6600,0xa6c1,0xa781,0x6740,0xa501,0x65c0,0x6480,0xa441,
0x6c00,0xacc1,0xad81,0x6d40,0xaf01,0x6fc0,0x6e80,0xae41,
0xaa01,0x6ac0,0x6b80,0xab41,0x6900,0xa9c1,0xa881,0x6840,
0x7800,0xb8c1,0xb981,0x7940,0xbb01,0x7bc0,0x7a80,0xba41,
0xbe01,0x7ec0,0x7f80,0xbf41,0x7d00,0xbdc1,0xbc81,0x7c40,
0xb401,0x74c0,0x7580,0xb541,0x7700,0xb7c1,0xb681,0x7640,
0x7200,0xb2c1,0xb381,0x7340,0xb101,0x71c0,0x7080,0xb041,
0x5000,0x90c1,0x9181,0x5140,0x9301,0x53c0,0x5280,0x9241,
0x9601,0x56c0,0x5780,0x9741,0x5500,0x95c1,0x9481,0x5440,
0x9c01,0x5cc0,0x5d80,0x9d41,0x5f00,0x9fc1,0x9e81,0x5e40,
0x5a00,0x9ac1,0x9b81,0x5b40,0x9901,0x59c0,0x5880,0x9841,
0x8801,0x48c0,0x4980,0x8941,0x4b00,0x8bc1,0x8a81,0x4a40,
0x4e00,0x8ec1,0x8f81,0x4f40,0x8d01,0x4dc0,0x4c80,0x8c41,
0x4400,0x84c1,0x8581,0x4540,0x8701,0x47c0,0x4680,0x8641,
0x8201,0x42c0,0x4380,0x8341,0x4100,0x81c1,0x8081,0x4040
};
//********************************************************************
unsigned int cal_crc(unsigned int ptr, unsigned int len)
{
unsigned int crc;
unsigned int da;
crc=0xffff;
while(len--)
{
da= (crc & 0xff); /* 以8 位二进制数的形式暂存CRC 的低8 位*/
crc>>=8; /* 右移8 位，相当于CRC 的高8 位*/
crc^=crc_tab[da^(Sci_VarRx[ptr])]; /* 低8位和当前字节异或后再查表求CRC ，再异或以前CRC */
ptr++;
}
return(crc);
}
我刚接触这一行,完全自学,希望各位不要笑我的问题弱智哦!谢谢!
我想问一下CRC余式表式自己做出来的吗?怎么做的 啊?我大概原理好像明白了,但是具体细节不太明白.还有做余式表的多项式式怎么规定的?不是有16和32的吗?不是固定的标准吗?
希望好心人尽快帮我解答这个疑问,谢谢了!