[ 摘要算法 ] CRC32原理, C实现 - 请路过的朋友帮助下！
本帖最后由 purplenight 于 2016-9-9 09:02 编辑感激不尽 http://www.360doc.com/content/14/0225/10/7775902_355489982.shtml 康小泡 发表于 2016-1-14 13:46
http://www.360doc.com/content/14/0225/10/7775902_355489982.shtml
找不到原因， 程序计算的CRC是错误的。 本帖最后由 purplenight 于 2016-7-16 11:21 编辑
关键在于文件打开方式
if ((fd=fopen(argv, "r")) == NULL)
r 计算 .txt CRC32正确, .c .exe均出错, 其他的文件格式未做测试。
rb计算 .txt .c .exeCRC32均正确.
好郁闷的一个下午。 #include <stdio.h>
#include <stdlib.h>
#include "inttypes.h"
#define Poly0xEDB88320L
static uint32_t crc_tab32;
static voidinit_crc32_tab(void);
uint32_t get_crc32(uint32_t crcinit, uint8_t * bs, uint32_t bssize);
uint32_t GetFileCRC(FILE *fd);
static void init_crc32_tab( void )
{
int i, j;
uint32_t crc;
for (i=0; i<256; i++)
{
crc = (unsigned long)i;
for (j=0; j<8; j++)
{
if ( crc & 0x00000001L )
crc = (crc >> 1) ^ Poly;
else
crc = crc >> 1;
}
crc_tab32 = crc;
}
}
uint32_t get_crc32(uint32_t crcinit, uint8_t * bs, uint32_t bssize)
{
uint32_t crc = crcinit ^ 0xffffffff;
init_crc32_tab();
while(bssize--)
crc = (crc >> 8) ^ crc_tab32[ (crc & 0xff) ^ *bs++];
return crc ^ 0xffffffff;
}
uint32_t GetFileCRC(FILE *fd)
{
uint32_t size = 16 * 1024;
uint8_t crcbuf;
uint32_t rdlen;
uint32_t crc = 0;
while ( (rdlen = fread(crcbuf, sizeof(uint8_t), size, fd)) > 0)
crc = get_crc32(crc, crcbuf, rdlen);
return crc;
}
int main(int argc, char **argv)
{
FILE*fd;
unsigned int value = 0;
chardrive;
chardir;
charfilename;
charext;
if(argc<2)
{
// 1. https://social.msdn.microsoft.com/Forums/vstudio/en-US/e2033f13-5172-4f2b-a4e6-0099c12755ed/dirnamebasename-equivalent-on-windows?forum=vcgeneral
// System::IO::Path::GetDirectoryName cannot be called from C.
// The closest function that I can think of is _splitpath
// 2. https://msdn.microsoft.com/en-us/library/e737s6tf.aspx
// 在编程过程中，常常需要获取程序的路径，并对路径进行分解和合并，
// 这时就使用到了_splitpath。同时与之相反的功能函数有：_makepath。与之相关的函数有：FindFirstFile等。
// if *nix
// printf("Usage: %s file", basename(argv) );
_splitpath(argv, drive, dir,filename,ext );
printf("Usage: %s file", filename );
exit(1);
}
if ((fd=fopen(argv, "rb")) == NULL)
{
perror("Error:");
exit(1);
}
value = GetFileCRC(fd);
printf("CRC: %X\n", value);
fclose(fd);
return 0;
} 感谢分享！努力学习！ 1. crc32
/*-
*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
*
*
* CRC32 code derived from work by Gary S. Brown.
*/
#include <sys/param.h>
#include <sys/systm.h>
static uint32_t crc32_tab[] = {
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(uint32_t crc, const void *buf, size_t size)
{
const uint8_t *p;
p = buf;
crc = crc ^ ~0U;
while (size--)
crc = crc32_tab[(crc ^ *p++) & 0xFF] ^ (crc >> 8);
return crc ^ ~0U;
}
link http://opensource.apple.com//source/xnu/xnu-1456.1.26/bsd/libkern/crc32.c
页:
[1]