user-0 提问: crc32算法求指点一二

回复:
user: user-1
content: 引用 12 楼 u011845833 的回复:引用 11 楼 ForestDB 的回复:如果不是练习，建议使用库函数。windows下有何crc32库函数么? 这个应该问Google。

user: user-0
content: 引用 10 楼 zhao4zhong1 的回复:这个挺好,感谢...

user: user-0
content: 引用 11 楼 ForestDB 的回复:如果不是练习，建议使用库函数。windows下有何crc32库函数么?

user: user-2
content: zlib难道不是windows下和linux下通用的？

user: user-1
content: 如果不是练习，建议使用库函数。

user: user-2
content: 引用 9 楼 u011845833 的回复:引用 8 楼 zhao4zhong1 的回复:zlib难道不是windows下和linux下通用的？这还真不知道耶,还没到你那个境界... http://blog.csdn.net/htttw/article/details/7616124

user: user-0
content: 引用 8 楼 zhao4zhong1 的回复:zlib难道不是windows下和linux下通用的？这还真不知道耶,还没到你那个境界...

user: user-0
content: 引用 1 楼 zhao4zhong1 的回复:参考zlib\crc32.h和zlib\crc32.c好的，正在安装vm...

user: user-2
content: 参考zlib\crc32.h和zlib\crc32.c

user: user-0
content: 引用 4 楼 my_live_123 的回复:提供两个曾经用过的，一个直接计算，一个查表法非常感谢你的回答，很有帮助．

user: user-0
content: 引用 3 楼 zhao4zhong1 的回复:我喜欢听话的孩纸。额，我想说，那个太复杂了，有木有简单点的，最好是windows下和linux下通用的...

user: user-3

user: user-4
content: 提供两个曾经用过的，一个直接计算，一个查表法  #include <stdio.h>  #define CRC_G 	0x04C11DB7  int crc32(unsigned int m) { 	unsigned int reg = 0; 	unsigned char tmp; 	int i; 	for(i = 0; i < 32; ++i) 	{ 		tmp = (m >> (31 - i) & 1) ^ ((reg >> 31) & 1); 		reg <<= 1; 		reg ^=  tmp * CRC_G; 		reg >>= 1; 		reg <<= 1; 		reg |= tmp; 	} 	printf("0x%x, ", reg);  	return 0; }  int gen_crc() { 	unsigned int i; 	printf("unsigned int crc32_table[65536 * 65536] = {\n"); 	for(i = 0; i < 65536; ++i) 	{ 		crc32(i); 		if((i + 1) % 8 == 0) 		printf("\n"); 		getchar(); 	} 	printf("};\n"); 	return 0; }  int main() { 	gen_crc(); 	return 0; }   差表法  /*  * $Id: crc32.c,v 1.1.1.1 1996/02/18 21:38:12 ylo Exp $  * $Log: crc32.c,v $  * Revision 1.1.1.1  1996/02/18 21:38:12  ylo  * 	Imported ssh-1.2.13.  *  * Revision 1.2  1995/07/13  01:21:34  ylo  * 	Added cvs log.  *  * $Endlog$  */  /* The implementation here was originally done by Gary S. Brown.  I have    borrowed the tables directly, and made some minor changes to the    crc32-function (including changing the interface). //ylo */    /* ============================================================= */   /*  COPYRIGHT (C) 1986 Gary S. Brown.  You may use this program, or       */   /*  code or tables extracted from it, as desired without restriction.     */   /*                                                                        */   /*  First, the polynomial itself and its table of feedback terms.  The    */   /*  polynomial is                                                         */   /*  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+X^0   */   /*                                                                        */   /*  Note that we take it "backwards" and put the highest-order term in    */   /*  the lowest-order bit.  The X^32 term is "implied"; the LSB is the     */   /*  X^31 term, etc.  The X^0 term (usually shown as "+1") results in      */   /*  the MSB being 1.                                                      */   /*                                                                        */   /*  Note that the usual hardware shift register implementation, which     */   /*  is what we're using (we're merely optimizing it by doing eight-bit    */   /*  chunks at a time) shifts bits into the lowest-order term.  In our     */   /*  implementation, that means shifting towards the right.  Why do we     */   /*  do it this way?  Because the calculated CRC must be transmitted in    */   /*  order from highest-order term to lowest-order term.  UARTs transmit   */   /*  characters in order from LSB to MSB.  By storing the CRC this way,    */   /*  we hand it to the UART in the order low-byte to high-byte; the UART   */   /*  sends each low-bit to hight-bit; and the result is transmission bit   */   /*  by bit from highest- to lowest-order term without requiring any bit   */   /*  shuffling on our part.  Reception works similarly.                    */   /*                                                                        */   /*  The feedback terms table consists of 256, 32-bit entries.  Notes:     */   /*                                                                        */   /*      The table can be generated at runtime if desired; code to do so   */   /*      is shown later.  It might not be obvious, but the feedback        */   /*      terms simply represent the results of eight shift/xor opera-      */   /*      tions for all combinations of data and CRC register values.       */   /*                                                                        */   /*      The values must be right-shifted by eight bits by the "updcrc"    */   /*      logic; the shift must be unsigned (bring in zeroes).  On some     */   /*      hardware you could probably optimize the shift in assembler by    */   /*      using byte-swap instructions.                                     */   /*      polynomial $edb88320                                              */   /*                                                                        */   /*  --------------------------------------------------------------------  */  static unsigned long crc32_tab[] = {       0x00000000L, 0x77073096L, 0xee0e612cL, 0x990951baL, 0x076dc419L,       0x706af48fL, 0xe963a535L, 0x9e6495a3L, 0x0edb8832L, 0x79dcb8a4L,       0xe0d5e91eL, 0x97d2d988L, 0x09b64c2bL, 0x7eb17cbdL, 0xe7b82d07L,       0x90bf1d91L, 0x1db71064L, 0x6ab020f2L, 0xf3b97148L, 0x84be41deL,       0x1adad47dL, 0x6ddde4ebL, 0xf4d4b551L, 0x83d385c7L, 0x136c9856L,       0x646ba8c0L, 0xfd62f97aL, 0x8a65c9ecL, 0x14015c4fL, 0x63066cd9L,       0xfa0f3d63L, 0x8d080df5L, 0x3b6e20c8L, 0x4c69105eL, 0xd56041e4L,       0xa2677172L, 0x3c03e4d1L, 0x4b04d447L, 0xd20d85fdL, 0xa50ab56bL,       0x35b5a8faL, 0x42b2986cL, 0xdbbbc9d6L, 0xacbcf940L, 0x32d86ce3L,       0x45df5c75L, 0xdcd60dcfL, 0xabd13d59L, 0x26d930acL, 0x51de003aL,       0xc8d75180L, 0xbfd06116L, 0x21b4f4b5L, 0x56b3c423L, 0xcfba9599L,       0xb8bda50fL, 0x2802b89eL, 0x5f058808L, 0xc60cd9b2L, 0xb10be924L,       0x2f6f7c87L, 0x58684c11L, 0xc1611dabL, 0xb6662d3dL, 0x76dc4190L,       0x01db7106L, 0x98d220bcL, 0xefd5102aL, 0x71b18589L, 0x06b6b51fL,       0x9fbfe4a5L, 0xe8b8d433L, 0x7807c9a2L, 0x0f00f934L, 0x9609a88eL,       0xe10e9818L, 0x7f6a0dbbL, 0x086d3d2dL, 0x91646c97L, 0xe6635c01L,       0x6b6b51f4L, 0x1c6c6162L, 0x856530d8L, 0xf262004eL, 0x6c0695edL,       0x1b01a57bL, 0x8208f4c1L, 0xf50fc457L, 0x65b0d9c6L, 0x12b7e950L,       0x8bbeb8eaL, 0xfcb9887cL, 0x62dd1ddfL, 0x15da2d49L, 0x8cd37cf3L,       0xfbd44c65L, 0x4db26158L, 0x3ab551ceL, 0xa3bc0074L, 0xd4bb30e2L,       0x4adfa541L, 0x3dd895d7L, 0xa4d1c46dL, 0xd3d6f4fbL, 0x4369e96aL,       0x346ed9fcL, 0xad678846L, 0xda60b8d0L, 0x44042d73L, 0x33031de5L,       0xaa0a4c5fL, 0xdd0d7cc9L, 0x5005713cL, 0x270241aaL, 0xbe0b1010L,       0xc90c2086L, 0x5768b525L, 0x206f85b3L, 0xb966d409L, 0xce61e49fL,       0x5edef90eL, 0x29d9c998L, 0xb0d09822L, 0xc7d7a8b4L, 0x59b33d17L,       0x2eb40d81L, 0xb7bd5c3bL, 0xc0ba6cadL, 0xedb88320L, 0x9abfb3b6L,       0x03b6e20cL, 0x74b1d29aL, 0xead54739L, 0x9dd277afL, 0x04db2615L,       0x73dc1683L, 0xe3630b12L, 0x94643b84L, 0x0d6d6a3eL, 0x7a6a5aa8L,       0xe40ecf0bL, 0x9309ff9dL, 0x0a00ae27L, 0x7d079eb1L, 0xf00f9344L,       0x8708a3d2L, 0x1e01f268L, 0x6906c2feL, 0xf762575dL, 0x806567cbL,       0x196c3671L, 0x6e6b06e7L, 0xfed41b76L, 0x89d32be0L, 0x10da7a5aL,       0x67dd4accL, 0xf9b9df6fL, 0x8ebeeff9L, 0x17b7be43L, 0x60b08ed5L,       0xd6d6a3e8L, 0xa1d1937eL, 0x38d8c2c4L, 0x4fdff252L, 0xd1bb67f1L,       0xa6bc5767L, 0x3fb506ddL, 0x48b2364bL, 0xd80d2bdaL, 0xaf0a1b4cL,       0x36034af6L, 0x41047a60L, 0xdf60efc3L, 0xa867df55L, 0x316e8eefL,       0x4669be79L, 0xcb61b38cL, 0xbc66831aL, 0x256fd2a0L, 0x5268e236L,       0xcc0c7795L, 0xbb0b4703L, 0x220216b9L, 0x5505262fL, 0xc5ba3bbeL,       0xb2bd0b28L, 0x2bb45a92L, 0x5cb36a04L, 0xc2d7ffa7L, 0xb5d0cf31L,       0x2cd99e8bL, 0x5bdeae1dL, 0x9b64c2b0L, 0xec63f226L, 0x756aa39cL,       0x026d930aL, 0x9c0906a9L, 0xeb0e363fL, 0x72076785L, 0x05005713L,       0x95bf4a82L, 0xe2b87a14L, 0x7bb12baeL, 0x0cb61b38L, 0x92d28e9bL,       0xe5d5be0dL, 0x7cdcefb7L, 0x0bdbdf21L, 0x86d3d2d4L, 0xf1d4e242L,       0x68ddb3f8L, 0x1fda836eL, 0x81be16cdL, 0xf6b9265bL, 0x6fb077e1L,       0x18b74777L, 0x88085ae6L, 0xff0f6a70L, 0x66063bcaL, 0x11010b5cL,       0x8f659effL, 0xf862ae69L, 0x616bffd3L, 0x166ccf45L, 0xa00ae278L,       0xd70dd2eeL, 0x4e048354L, 0x3903b3c2L, 0xa7672661L, 0xd06016f7L,       0x4969474dL, 0x3e6e77dbL, 0xaed16a4aL, 0xd9d65adcL, 0x40df0b66L,       0x37d83bf0L, 0xa9bcae53L, 0xdebb9ec5L, 0x47b2cf7fL, 0x30b5ffe9L,       0xbdbdf21cL, 0xcabac28aL, 0x53b39330L, 0x24b4a3a6L, 0xbad03605L,       0xcdd70693L, 0x54de5729L, 0x23d967bfL, 0xb3667a2eL, 0xc4614ab8L,       0x5d681b02L, 0x2a6f2b94L, 0xb40bbe37L, 0xc30c8ea1L, 0x5a05df1bL,       0x2d02ef8dL    };  /* Return a 32-bit CRC of the contents of the buffer. */  unsigned long crc32(const unsigned char *s, unsigned int len) {   unsigned int i;   unsigned long crc32val;      crc32val = 0;   for (i = 0;  i < len;  i ++)     {       crc32val = 	crc32_tab[(crc32val ^ s[i]) & 0xff] ^ 	  (crc32val >> 8);     }   return crc32val; }

user: user-2
content: 引用 2 楼 u011845833 的回复:引用 1 楼 zhao4zhong1 的回复:参考zlib\crc32.h和zlib\crc32.c好的，正在安装vm... 我喜欢听话的孩纸。