CRC 简介

CRC wiki，历史发展，各个版本的用途 等
https://en.wikipedia.org/wiki/Cyclic_redundancy_check

(apple)crc32.c

/*
 * This code implements the AUTODIN II polynomial used by Ethernet,
 * and can be used to calculate multicast address hash indices.
 * It assumes that the low order bits will be transmitted first,
 * and consequently the low byte should be sent first when
 * the crc computation is finished.  The crc should be complemented
 * before transmission.
 * The variable corresponding to the macro argument "crc" should
 * be an unsigned long and should be preset to all ones for Ethernet
 * use.  An error-free packet will leave 0xDEBB20E3 in the crc.
 *			Spencer Garrett <srg@quick.com>
 */

#include <sys/cdefs.h>
__FBSDID("$FreeBSD: src/usr.bin/cksum/crc32.c,v 1.9 2003/03/13 23:32:28 robert Exp $");

#include <sys/types.h>

#include <stdio.h>
#include <stdint.h>
#include <unistd.h>

#include "extern.h"

#define CRC(crc, ch)	 (crc = (crc >> 8) ^ crctab[(crc ^ (ch)) & 0xff])

/* generated using the AUTODIN II polynomial
 *	x^32 + x^26 + x^23 + x^22 + x^16 +
 *	x^12 + x^11 + x^10 + x^8 + x^7 + x^5 + x^4 + x^2 + x^1 + 1
 */
static const uint32_t crctab[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,
};

uint32_t crc32_total = 0;

int
crc32(int fd, uint32_t *cval, off_t *clen)
{
    uint32_t lcrc = ~0;
    int nr ;
    off_t len ;
    char buf[BUFSIZ], *p ;
	
    len = 0 ;
    crc32_total = ~crc32_total ;
    while ((nr = read(fd, buf, sizeof(buf))) > 0)
        for (len += nr, p = buf; nr--; ++p) {
	    CRC(lcrc, *p) ;
	    CRC(crc32_total, *p) ;
	}
    if (nr < 0)
        return 1 ;

    *clen = len ;
    *cval = ~lcrc ;
    crc32_total = ~crc32_total ;
    return 0 ;
}

crc16

        //c# 
        public static byte[] CRC16(string sInputString)
        {
            byte[] data = System.Text.ASCIIEncoding.ASCII.GetBytes(sInputString);
            int len = data.Length;
            if (len > 0)
            {
                ushort crc = 0xFFFF;

                for (int i = 0; i < len; i++)
                {
                    crc = (ushort)(crc ^ (data[i]));
                    for (int j = 0; j < 8; j++)
                    {
                        crc = (crc & 1) != 0 ? (ushort)((crc >> 1) ^ 0xA001) : (ushort)(crc >> 1);
                    }
                }
                byte hi = (byte)((crc & 0xFF00) >> 8);  //高位置
                byte lo = (byte)(crc & 0x00FF);         //低位置

                return new byte[] { hi, lo };
            }
            return new byte[] { 0, 0 };
        }

crc32 c#

//生成CRC32码表
        protected static UInt64[] Crc32Table;
        public static void GetCRC32Table()
        {
            UInt64 Crc;
            Crc32Table = new UInt64[256];
            int i, j;
            for (i = 0; i < 256; i++)
            {
                Crc = (ulong)i;
                for (j = 8; j > 0; j--)
                {
                    if ((Crc & 1) == 1)
                        Crc = (Crc >> 1) ^ 0xEDB88320;
                    else
                        Crc >>= 1;
                }
                Crc32Table[i] = Crc;
            }
        }
       

        //获取字符串的CRC32校验值
        public static UInt64 GetCRC32Str(string sInputString)
        {
            //生成码表
            //GetCRC32Table();
            byte[] buffer = System.Text.ASCIIEncoding.ASCII.GetBytes(sInputString);
            UInt64 value = 0xffffffff;
            int len = buffer.Length;
            for (int i = 0; i < len; i++)
            {
                value = (value >> 8) ^ Crc32Table[(value & 0xFF) ^ buffer[i]];
            }
            return value ^ 0xffffffff;
        }

        public static UInt32 GetCRC32ByteArray(Byte[] buffer, Int32 bufLen)
        {
            //生成码表
            //GetCRC32Table();
            //byte[] buffer = System.Text.ASCIIEncoding.ASCII.GetBytes(sInputString);

            UInt64 value = 0xffffffff;
            int len = bufLen;
            for (int i = 0; i < len; i++)
            {
                value = (value >> 8) ^ Crc32Table[(value & 0xFF) ^ buffer[i]];
            }
            UInt64 ret= value ^ 0xffffffff;

            /*
            Byte[] Buf64 = BitConverter.GetBytes(ret);//16
            Byte[] Buf32 = new Byte[4];

            UInt64 crc32 = BitConverter.ToUInt32(Buf32);
           */

            return (UInt32)ret;
        }