CRC32 和 CRC16 校验算法是编程中最常用的哈希算法,他们的实现很简单,下面是以前封装的 CRC32 和 CRC16 算法。

头文件的实现如下:

/************************************************************************
*
*    File Name:        crc.h
*    Description:    crc checksum
*
*    Version:        V1.00
*    Author:            程建喜
*    Create Time:    2013-07-20
*
*************************************************************************/

#ifndef CRC_H
#define CRC_H

// This function group is a 16-bit cache conserving (16 entry table) implementation of the CRC-16-CCITT algorithm.

unsigned short crc16_init();

void crc16(const char* data, unsigned int len, unsigned short& crc);

void crc16_result(unsigned short& crc);


// CRC-32
unsigned long crc32_init();

void crc32(const char* data, unsigned int len, unsigned long& crc);

#ifdef Q_OS_WIN32
void crc32_assembly(const char* data, unsigned int len, unsigned long& crc);
#endif

void crc32_result(unsigned long& crc);

#endif // CRC_H

CPP 文件的实现如下:

/************************************************************************
*
*    File Name:        crc.cpp
*    Description:    crc checksum
*
*    Version:        V1.00
*    Author:            程建喜
*    Create Time:    2013-07-20
*
*************************************************************************/

#include "crc.h"

// Static CRC16 table
static const unsigned short crc16_tbl[16] = {
    0x0000, 0x1081, 0x2102, 0x3183,
    0x4204, 0x5285, 0x6306, 0x7387,
    0x8408, 0x9489, 0xa50a, 0xb58b,
    0xc60c, 0xd68d, 0xe70e, 0xf78f
};

// Static CRC32 table
static const unsigned long crc32_tbl[256] =
{
    0x00000000, 0x77073096, 0xEE0E612C, 0x990951BA,
    0x076DC419, 0x706AF48F, 0xE963A535, 0x9E6495A3,
    0x0EDB8832, 0x79DCB8A4, 0xE0D5E91E, 0x97D2D988,
    0x09B64C2B, 0x7EB17CBD, 0xE7B82D07, 0x90BF1D91,
    0x1DB71064, 0x6AB020F2, 0xF3B97148, 0x84BE41DE,
    0x1ADAD47D, 0x6DDDE4EB, 0xF4D4B551, 0x83D385C7,
    0x136C9856, 0x646BA8C0, 0xFD62F97A, 0x8A65C9EC,
    0x14015C4F, 0x63066CD9, 0xFA0F3D63, 0x8D080DF5,
    0x3B6E20C8, 0x4C69105E, 0xD56041E4, 0xA2677172,
    0x3C03E4D1, 0x4B04D447, 0xD20D85FD, 0xA50AB56B,
    0x35B5A8FA, 0x42B2986C, 0xDBBBC9D6, 0xACBCF940,
    0x32D86CE3, 0x45DF5C75, 0xDCD60DCF, 0xABD13D59,
    0x26D930AC, 0x51DE003A, 0xC8D75180, 0xBFD06116,
    0x21B4F4B5, 0x56B3C423, 0xCFBA9599, 0xB8BDA50F,
    0x2802B89E, 0x5F058808, 0xC60CD9B2, 0xB10BE924,
    0x2F6F7C87, 0x58684C11, 0xC1611DAB, 0xB6662D3D,

    0x76DC4190, 0x01DB7106, 0x98D220BC, 0xEFD5102A,
    0x71B18589, 0x06B6B51F, 0x9FBFE4A5, 0xE8B8D433,
    0x7807C9A2, 0x0F00F934, 0x9609A88E, 0xE10E9818,
    0x7F6A0DBB, 0x086D3D2D, 0x91646C97, 0xE6635C01,
    0x6B6B51F4, 0x1C6C6162, 0x856530D8, 0xF262004E,
    0x6C0695ED, 0x1B01A57B, 0x8208F4C1, 0xF50FC457,
    0x65B0D9C6, 0x12B7E950, 0x8BBEB8EA, 0xFCB9887C,
    0x62DD1DDF, 0x15DA2D49, 0x8CD37CF3, 0xFBD44C65,
    0x4DB26158, 0x3AB551CE, 0xA3BC0074, 0xD4BB30E2,
    0x4ADFA541, 0x3DD895D7, 0xA4D1C46D, 0xD3D6F4FB,
    0x4369E96A, 0x346ED9FC, 0xAD678846, 0xDA60B8D0,
    0x44042D73, 0x33031DE5, 0xAA0A4C5F, 0xDD0D7CC9,
    0x5005713C, 0x270241AA, 0xBE0B1010, 0xC90C2086,
    0x5768B525, 0x206F85B3, 0xB966D409, 0xCE61E49F,
    0x5EDEF90E, 0x29D9C998, 0xB0D09822, 0xC7D7A8B4,
    0x59B33D17, 0x2EB40D81, 0xB7BD5C3B, 0xC0BA6CAD,

    0xEDB88320, 0x9ABFB3B6, 0x03B6E20C, 0x74B1D29A,
    0xEAD54739, 0x9DD277AF, 0x04DB2615, 0x73DC1683,
    0xE3630B12, 0x94643B84, 0x0D6D6A3E, 0x7A6A5AA8,
    0xE40ECF0B, 0x9309FF9D, 0x0A00AE27, 0x7D079EB1,
    0xF00F9344, 0x8708A3D2, 0x1E01F268, 0x6906C2FE,
    0xF762575D, 0x806567CB, 0x196C3671, 0x6E6B06E7,
    0xFED41B76, 0x89D32BE0, 0x10DA7A5A, 0x67DD4ACC,
    0xF9B9DF6F, 0x8EBEEFF9, 0x17B7BE43, 0x60B08ED5,
    0xD6D6A3E8, 0xA1D1937E, 0x38D8C2C4, 0x4FDFF252,
    0xD1BB67F1, 0xA6BC5767, 0x3FB506DD, 0x48B2364B,
    0xD80D2BDA, 0xAF0A1B4C, 0x36034AF6, 0x41047A60,
    0xDF60EFC3, 0xA867DF55, 0x316E8EEF, 0x4669BE79,
    0xCB61B38C, 0xBC66831A, 0x256FD2A0, 0x5268E236,
    0xCC0C7795, 0xBB0B4703, 0x220216B9, 0x5505262F,
    0xC5BA3BBE, 0xB2BD0B28, 0x2BB45A92, 0x5CB36A04,
    0xC2D7FFA7, 0xB5D0CF31, 0x2CD99E8B, 0x5BDEAE1D,

    0x9B64C2B0, 0xEC63F226, 0x756AA39C, 0x026D930A,
    0x9C0906A9, 0xEB0E363F, 0x72076785, 0x05005713,
    0x95BF4A82, 0xE2B87A14, 0x7BB12BAE, 0x0CB61B38,
    0x92D28E9B, 0xE5D5BE0D, 0x7CDCEFB7, 0x0BDBDF21,
    0x86D3D2D4, 0xF1D4E242, 0x68DDB3F8, 0x1FDA836E,
    0x81BE16CD, 0xF6B9265B, 0x6FB077E1, 0x18B74777,
    0x88085AE6, 0xFF0F6A70, 0x66063BCA, 0x11010B5C,
    0x8F659EFF, 0xF862AE69, 0x616BFFD3, 0x166CCF45,
    0xA00AE278, 0xD70DD2EE, 0x4E048354, 0x3903B3C2,
    0xA7672661, 0xD06016F7, 0x4969474D, 0x3E6E77DB,
    0xAED16A4A, 0xD9D65ADC, 0x40DF0B66, 0x37D83BF0,
    0xA9BCAE53, 0xDEBB9EC5, 0x47B2CF7F, 0x30B5FFE9,
    0xBDBDF21C, 0xCABAC28A, 0x53B39330, 0x24B4A3A6,
    0xBAD03605, 0xCDD70693, 0x54DE5729, 0x23D967BF,
    0xB3667A2E, 0xC4614AB8, 0x5D681B02, 0x2A6F2B94,
    0xB40BBE37, 0xC30C8EA1, 0x5A05DF1B, 0x2D02EF8D,
};

unsigned short crc16_init()
{
    return 0xffff;
}

void crc16(const char *data, unsigned int len, unsigned short& crc)
{
    unsigned char c;
    const unsigned char *p = reinterpret_cast<const unsigned char *>(data);
    while (len--)
    {
        c = *p++;
        crc = ((crc >> 4) & 0x0fff) ^ crc16_tbl[((crc ^ c) & 15)];
        c >>= 4;
        crc = ((crc >> 4) & 0x0fff) ^ crc16_tbl[((crc ^ c) & 15)];
    }

}

void crc16_result(unsigned short& crc)
{
    crc = ~crc & 0xffff;
}


unsigned long crc32_init()
{
    return 0xFFFFFFFF;
}


void crc32(const char *data, unsigned int len, unsigned long &crc)
{
    unsigned char c;
    const unsigned char *p = reinterpret_cast<const unsigned char *>(data);
    while (len--)
    {
        c = *p++;
        crc = (crc >> 8) ^ crc32_tbl[c ^ (crc & 0xFF)];
    }
}

#ifdef Q_OS_WIN32
void crc32_assembly(const char *data, unsigned int len, unsigned long &crc)
{
    if (len > 0 && len <= 65536*2)
    {
        // There is a bug in the Microsoft compilers where inline assembly
        // code cannot access static member variables.  This is a work around
        // for that bug.
        const void* ptrCrc32Table = reinterpret_cast<const void*>(&crc32_tbl);

        // Register use:
        //        eax - CRC32 value
        //        ebx - a lot of things
        //        ecx - CRC32 value
        //        edx - address of end of buffer
        //        esi - address of start of buffer
        //        edi - CRC32 table
        __asm
        {
            // Save the esi and edi registers
            push esi
            push edi

            mov eax, crc                // Load the pointer to dwCrc32
            mov ecx, [eax]                // Dereference the pointer to load dwCrc32

            mov edi, ptrCrc32Table        // Load the CRC32 table

            mov esi, data                // Load buffer(此处 mov 源代码为 lea)
            mov ebx, len                // Load dwBytesRead
            lea edx, [esi + ebx]        // Calculate the end of the buffer

            crc32loop:
            xor eax, eax                // Clear the eax register
            mov bl, byte ptr [esi]        // Load the current source byte

            mov al, cl                    // Copy crc value into eax
            inc esi                        // Advance the source pointer

            xor al, bl                    // Create the index into the CRC32 table
            shr ecx, 8

            mov ebx, [edi + eax * 4]    // Get the value out of the table
            xor ecx, ebx                // xor with the current byte

            cmp edx, esi                // Have we reached the end of the buffer?
            jne crc32loop

            // Restore the edi and esi registers
            pop edi
            pop esi

            mov eax, crc                // Load the pointer to dwCrc32
            mov [eax], ecx                // Write the resul
        }
    }
}
#endif

void crc32_result(unsigned long &crc)
{
    crc = ~crc;
}

标签: CRC32, CRC16, CRC

添加新评论