串口通讯中CRC32校验实现

也是在博客园看到的一篇文章，那里直接贴了代码，我载下来试验了，并做了小的修改

CRC校验试循环冗余的，每次都计算一个校验会消耗很多时间，因此这个方法中事先算好了一个CRC32table，存储256个CRC数据，需要用到的时候直接查表而不需要重新计算，节省不少时间，代码如下：

//#include "stdafx.h"
#include <stdio.h>
#include <windows.h>
#include <string.h>

const unsigned long globe_Crc32Table[256]={
        0x00000000,0x04c11db7,0x09823b6e,0x0d4326d9,0x130476dc,0x17c56b6b,0x1a864db2,0x1e475005,
        0x2608edb8,0x22c9f00f,0x2f8ad6d6,0x2b4bcb61,0x350c9b64,0x31cd86d3,0x3c8ea00a,0x384fbdbd,
        0x4c11db70,0x48d0c6c7,0x4593e01e,0x4152fda9,0x5f15adac,0x5bd4b01b,0x569796c2,0x52568b75,
        0x6a1936c8,0x6ed82b7f,0x639b0da6,0x675a1011,0x791d4014,0x7ddc5da3,0x709f7b7a,0x745e66cd,
        0x9823b6e0,0x9ce2ab57,0x91a18d8e,0x95609039,0x8b27c03c,0x8fe6dd8b,0x82a5fb52,0x8664e6e5,
        0xbe2b5b58,0xbaea46ef,0xb7a96036,0xb3687d81,0xad2f2d84,0xa9ee3033,0xa4ad16ea,0xa06c0b5d,
        0xd4326d90,0xd0f37027,0xddb056fe,0xd9714b49,0xc7361b4c,0xc3f706fb,0xceb42022,0xca753d95,
        0xf23a8028,0xf6fb9d9f,0xfbb8bb46,0xff79a6f1,0xe13ef6f4,0xe5ffeb43,0xe8bccd9a,0xec7dd02d,
        0x34867077,0x30476dc0,0x3d044b19,0x39c556ae,0x278206ab,0x23431b1c,0x2e003dc5,0x2ac12072,
        0x128e9dcf,0x164f8078,0x1b0ca6a1,0x1fcdbb16,0x018aeb13,0x054bf6a4,0x0808d07d,0x0cc9cdca,
        0x7897ab07,0x7c56b6b0,0x71159069,0x75d48dde,0x6b93dddb,0x6f52c06c,0x6211e6b5,0x66d0fb02,
        0x5e9f46bf,0x5a5e5b08,0x571d7dd1,0x53dc6066,0x4d9b3063,0x495a2dd4,0x44190b0d,0x40d816ba,
        0xaca5c697,0xa864db20,0xa527fdf9,0xa1e6e04e,0xbfa1b04b,0xbb60adfc,0xb6238b25,0xb2e29692,
        0x8aad2b2f,0x8e6c3698,0x832f1041,0x87ee0df6,0x99a95df3,0x9d684044,0x902b669d,0x94ea7b2a,
        0xe0b41de7,0xe4750050,0xe9362689,0xedf73b3e,0xf3b06b3b,0xf771768c,0xfa325055,0xfef34de2,
        0xc6bcf05f,0xc27dede8,0xcf3ecb31,0xcbffd686,0xd5b88683,0xd1799b34,0xdc3abded,0xd8fba05a,
        0x690ce0ee,0x6dcdfd59,0x608edb80,0x644fc637,0x7a089632,0x7ec98b85,0x738aad5c,0x774bb0eb,
        0x4f040d56,0x4bc510e1,0x46863638,0x42472b8f,0x5c007b8a,0x58c1663d,0x558240e4,0x51435d53,
        0x251d3b9e,0x21dc2629,0x2c9f00f0,0x285e1d47,0x36194d42,0x32d850f5,0x3f9b762c,0x3b5a6b9b,
        0x0315d626,0x07d4cb91,0x0a97ed48,0x0e56f0ff,0x1011a0fa,0x14d0bd4d,0x19939b94,0x1d528623,
        0xf12f560e,0xf5ee4bb9,0xf8ad6d60,0xfc6c70d7,0xe22b20d2,0xe6ea3d65,0xeba91bbc,0xef68060b,
        0xd727bbb6,0xd3e6a601,0xdea580d8,0xda649d6f,0xc423cd6a,0xc0e2d0dd,0xcda1f604,0xc960ebb3,
        0xbd3e8d7e,0xb9ff90c9,0xb4bcb610,0xb07daba7,0xae3afba2,0xaafbe615,0xa7b8c0cc,0xa379dd7b,
        0x9b3660c6,0x9ff77d71,0x92b45ba8,0x9675461f,0x8832161a,0x8cf30bad,0x81b02d74,0x857130c3,
        0x5d8a9099,0x594b8d2e,0x5408abf7,0x50c9b640,0x4e8ee645,0x4a4ffbf2,0x470cdd2b,0x43cdc09c,
        0x7b827d21,0x7f436096,0x7200464f,0x76c15bf8,0x68860bfd,0x6c47164a,0x61043093,0x65c52d24,
        0x119b4be9,0x155a565e,0x18197087,0x1cd86d30,0x029f3d35,0x065e2082,0x0b1d065b,0x0fdc1bec,
        0x3793a651,0x3352bbe6,0x3e119d3f,0x3ad08088,0x2497d08d,0x2056cd3a,0x2d15ebe3,0x29d4f654,
        0xc5a92679,0xc1683bce,0xcc2b1d17,0xc8ea00a0,0xd6ad50a5,0xd26c4d12,0xdf2f6bcb,0xdbee767c,
        0xe3a1cbc1,0xe760d676,0xea23f0af,0xeee2ed18,0xf0a5bd1d,0xf464a0aa,0xf9278673,0xfde69bc4,
        0x89b8fd09,0x8d79e0be,0x803ac667,0x84fbdbd0,0x9abc8bd5,0x9e7d9662,0x933eb0bb,0x97ffad0c,
        0xafb010b1,0xab710d06,0xa6322bdf,0xa2f33668,0xbcb4666d,0xb8757bda,0xb5365d03,0xb1f740b4
};

DWORD Crc32(LPBYTE pData, int length)
{
    UINT unResult;
    
    if( 0 == length-- ) 
        return (DWORD)-1;
    unResult = *pData++ << 24;
    if( length-- )
    {
        unResult |= *pData++ << 16;
        if( length-- )
        {
            unResult |= *pData++ << 8;
            if( length-- ) unResult |= *pData++;
        }
    }
    unResult = ~ unResult;
    
    while( length-- )
    {
        unResult = (unResult << 8 | *pData) ^ globe_Crc32Table[unResult >> 24];
        pData++;
    }
    
    return ~unResult;
}

int main()
{
    char *aa = "1234567afwerqwerasdfwe";
    char *bb = "123457afwerqwerasdfwe";
    
    DWORD dw_aa = Crc32((LPBYTE)aa,strlen(aa));
    DWORD dw_bb = Crc32((LPBYTE)bb,strlen(bb));
    
    return 0;
}

试验结果成功，原本的Crc32函数是只传第一个参数的，没有length，根据字符是否为'\0'确定是否结束计算，但是小人认为，由于在用于文件传输时不可避免会出现'\0'现象，增加一个DATAlength参数可以使Crc32用于文件传输。

原文地址：http://www.cnblogs.com/lancidie/archive/2012/01/01/2309309.html