[已解决][ 摘要算法 ] CRC32原理, C实现 - 请路过的朋友帮助下！

purplenight

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康小泡

2016-1-14 13:46:51

http://www.360doc.com/content/14/0225/10/7775902_355489982.shtml

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康小泡

http://www.360doc.com/content/14/0225/10/7775902_355489982.shtml

purplenight

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。

purplenight

关键在于文件打开方式

1. if ((fd=fopen(argv[1], "r")) == NULL)

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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 .exe  CRC32均正确.

好郁闷的一个下午。

purplenight

1. #include    <stdio.h>
   
2. #include    <stdlib.h>
   
3. #include    "inttypes.h"
   
4. 
   
5. #define     Poly  0xEDB88320L
   
6. 
   
7. static      uint32_t    crc_tab32[256];
   
8. static      void  init_crc32_tab(void);
   
9. 
   
10. uint32_t    get_crc32(uint32_t crcinit, uint8_t * bs, uint32_t bssize);
    
11. uint32_t    GetFileCRC(FILE *fd);
    
12. 
    
13. static void init_crc32_tab( void )
    
14. {
    
15.       int   i, j;
    
16.       uint32_t    crc;
    
17. 
    
18.       for (i=0; i<256; i++)
    
19.       {
    
20.             crc = (unsigned long)i;
    
21.             for (j=0; j<8; j++)
    
22.             {
    
23.                   if ( crc & 0x00000001L )
    
24.                         crc = (crc >> 1) ^ Poly;
    
25.                   else
    
26.                         crc = crc >> 1;
    
27.             }
    
28.             crc_tab32[i] = crc;
    
29.       }
    
30. }
    
31. 
    
32. uint32_t    get_crc32(uint32_t crcinit, uint8_t * bs, uint32_t bssize)
    
33. {
    
34.       uint32_t    crc = crcinit ^ 0xffffffff;
    
35. 
    
36.       init_crc32_tab();
    
37.       while(bssize--)
    
38.             crc = (crc >> 8) ^ crc_tab32[ (crc & 0xff) ^ *bs++];
    
39. 
    
40.       return crc ^ 0xffffffff;
    
41. }
    
42. 
    
43. uint32_t GetFileCRC(FILE *fd)
    
44. {
    
45.       uint32_t size = 16 * 1024;
    
46.       uint8_t crcbuf[16*1024];
    
47.       uint32_t rdlen;
    
48.       uint32_t crc = 0;
    
49. 
    
50.       while ( (rdlen = fread(crcbuf, sizeof(uint8_t), size, fd)) > 0)
    
51.             crc = get_crc32(crc, crcbuf, rdlen);
    
52. 
    
53.       return crc;
    
54. }
    
55. 
    
56. int main(int argc, char **argv)
    
57. {
    
58.       FILE  *fd;
    
59.       unsigned int value = 0;
    
60.       char  drive[8];
    
61.       char  dir[32];
    
62.       char  filename[32];
    
63.       char  ext[8];
    
64. 
    
65.       if(argc<2)
    
66.       {
    
67. //     1.     https://social.msdn.microsoft.com/Forums/vstudio/en-US/e2033f13-5172-4f2b-a4e6-0099c12755ed/dirnamebasename-equivalent-on-windows?forum=vcgeneral
    
68. //            System::IO::Path::GetDirectoryName cannot be called from C.
    
69. //            The closest function that I can think of is _splitpath
    
70. 
    
71. //     2.     https://msdn.microsoft.com/en-us/library/e737s6tf.aspx
    
72. 
    
73. //          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，
    
74. //          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。
    
75. //    if *nix
    
76. //          printf("Usage: %s file", basename(argv[0]) );
    
77. 
    
78.             _splitpath(argv[0], drive, dir,  filename,ext );
    
79.             printf("Usage: %s file", filename );
    
80.             exit(1);
    
81.       }
    
82.       if ((fd=fopen(argv[1], "rb")) == NULL)
    
83.       {
    
84.             perror("Error:");
    
85.             exit(1);
    
86.       }
    
87. 
    
88.       value = GetFileCRC(fd);
    
89.       printf("CRC: %X\n", value);
    
90. 
    
91.       fclose(fd);
    
92.       return 0;
    
93. }

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辅助初学者

感谢分享！努力学习！

purplenight

1. crc32

1. /*-
   
2. *  COPYRIGHT (C) 1986 Gary S. Brown.  You may use this program, or
   
3. *  code or tables extracted from it, as desired without restriction.
   
4. *
   
5. *  First, the polynomial itself and its table of feedback terms.  The
   
6. *  polynomial is
   
7. *  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
   
8. *
   
9. *  Note that we take it "backwards" and put the highest-order term in
   
10. *  the lowest-order bit.  The X^32 term is "implied"; the LSB is the
    
11. *  X^31 term, etc.  The X^0 term (usually shown as "+1") results in
    
12. *  the MSB being 1
    
13. *
    
14. *  Note that the usual hardware shift register implementation, which
    
15. *  is what we're using (we're merely optimizing it by doing eight-bit
    
16. *  chunks at a time) shifts bits into the lowest-order term.  In our
    
17. *  implementation, that means shifting towards the right.  Why do we
    
18. *  do it this way?  Because the calculated CRC must be transmitted in
    
19. *  order from highest-order term to lowest-order term.  UARTs transmit
    
20. *  characters in order from LSB to MSB.  By storing the CRC this way
    
21. *  we hand it to the UART in the order low-byte to high-byte; the UART
    
22. *  sends each low-bit to hight-bit; and the result is transmission bit
    
23. *  by bit from highest- to lowest-order term without requiring any bit
    
24. *  shuffling on our part.  Reception works similarly
    
25. *
    
26. *  The feedback terms table consists of 256, 32-bit entries.  Notes
    
27. *
    
28. *      The table can be generated at runtime if desired; code to do so
    
29. *      is shown later.  It might not be obvious, but the feedback
    
30. *      terms simply represent the results of eight shift/xor opera
    
31. *      tions for all combinations of data and CRC register values
    
32. *
    
33. *      The values must be right-shifted by eight bits by the "updcrc
    
34. *      logic; the shift must be unsigned (bring in zeroes).  On some
    
35. *      hardware you could probably optimize the shift in assembler by
    
36. *      using byte-swap instructions
    
37. *      polynomial $edb88320
    
38. *
    
39. *
    
40. * CRC32 code derived from work by Gary S. Brown.
    
41. */
    
42. 
    
43. #include <sys/param.h>
    
44. #include <sys/systm.h>
    
45. 
    
46. static uint32_t crc32_tab[] = {
    
47.         0x00000000, 0x77073096, 0xee0e612c, 0x990951ba, 0x076dc419, 0x706af48f,
    
48.         0xe963a535, 0x9e6495a3,        0x0edb8832, 0x79dcb8a4, 0xe0d5e91e, 0x97d2d988,
    
49.         0x09b64c2b, 0x7eb17cbd, 0xe7b82d07, 0x90bf1d91, 0x1db71064, 0x6ab020f2,
    
50.         0xf3b97148, 0x84be41de,        0x1adad47d, 0x6ddde4eb, 0xf4d4b551, 0x83d385c7,
    
51.         0x136c9856, 0x646ba8c0, 0xfd62f97a, 0x8a65c9ec,        0x14015c4f, 0x63066cd9,
    
52.         0xfa0f3d63, 0x8d080df5,        0x3b6e20c8, 0x4c69105e, 0xd56041e4, 0xa2677172,
    
53.         0x3c03e4d1, 0x4b04d447, 0xd20d85fd, 0xa50ab56b,        0x35b5a8fa, 0x42b2986c,
    
54.         0xdbbbc9d6, 0xacbcf940,        0x32d86ce3, 0x45df5c75, 0xdcd60dcf, 0xabd13d59,
    
55.         0x26d930ac, 0x51de003a, 0xc8d75180, 0xbfd06116, 0x21b4f4b5, 0x56b3c423,
    
56.         0xcfba9599, 0xb8bda50f, 0x2802b89e, 0x5f058808, 0xc60cd9b2, 0xb10be924,
    
57.         0x2f6f7c87, 0x58684c11, 0xc1611dab, 0xb6662d3d,        0x76dc4190, 0x01db7106,
    
58.         0x98d220bc, 0xefd5102a, 0x71b18589, 0x06b6b51f, 0x9fbfe4a5, 0xe8b8d433,
    
59.         0x7807c9a2, 0x0f00f934, 0x9609a88e, 0xe10e9818, 0x7f6a0dbb, 0x086d3d2d,
    
60.         0x91646c97, 0xe6635c01, 0x6b6b51f4, 0x1c6c6162, 0x856530d8, 0xf262004e,
    
61.         0x6c0695ed, 0x1b01a57b, 0x8208f4c1, 0xf50fc457, 0x65b0d9c6, 0x12b7e950,
    
62.         0x8bbeb8ea, 0xfcb9887c, 0x62dd1ddf, 0x15da2d49, 0x8cd37cf3, 0xfbd44c65,
    
63.         0x4db26158, 0x3ab551ce, 0xa3bc0074, 0xd4bb30e2, 0x4adfa541, 0x3dd895d7,
    
64.         0xa4d1c46d, 0xd3d6f4fb, 0x4369e96a, 0x346ed9fc, 0xad678846, 0xda60b8d0,
    
65.         0x44042d73, 0x33031de5, 0xaa0a4c5f, 0xdd0d7cc9, 0x5005713c, 0x270241aa,
    
66.         0xbe0b1010, 0xc90c2086, 0x5768b525, 0x206f85b3, 0xb966d409, 0xce61e49f,
    
67.         0x5edef90e, 0x29d9c998, 0xb0d09822, 0xc7d7a8b4, 0x59b33d17, 0x2eb40d81,
    
68.         0xb7bd5c3b, 0xc0ba6cad, 0xedb88320, 0x9abfb3b6, 0x03b6e20c, 0x74b1d29a,
    
69.         0xead54739, 0x9dd277af, 0x04db2615, 0x73dc1683, 0xe3630b12, 0x94643b84,
    
70.         0x0d6d6a3e, 0x7a6a5aa8, 0xe40ecf0b, 0x9309ff9d, 0x0a00ae27, 0x7d079eb1,
    
71.         0xf00f9344, 0x8708a3d2, 0x1e01f268, 0x6906c2fe, 0xf762575d, 0x806567cb,
    
72.         0x196c3671, 0x6e6b06e7, 0xfed41b76, 0x89d32be0, 0x10da7a5a, 0x67dd4acc,
    
73.         0xf9b9df6f, 0x8ebeeff9, 0x17b7be43, 0x60b08ed5, 0xd6d6a3e8, 0xa1d1937e,
    
74.         0x38d8c2c4, 0x4fdff252, 0xd1bb67f1, 0xa6bc5767, 0x3fb506dd, 0x48b2364b,
    
75.         0xd80d2bda, 0xaf0a1b4c, 0x36034af6, 0x41047a60, 0xdf60efc3, 0xa867df55,
    
76.         0x316e8eef, 0x4669be79, 0xcb61b38c, 0xbc66831a, 0x256fd2a0, 0x5268e236,
    
77.         0xcc0c7795, 0xbb0b4703, 0x220216b9, 0x5505262f, 0xc5ba3bbe, 0xb2bd0b28,
    
78.         0x2bb45a92, 0x5cb36a04, 0xc2d7ffa7, 0xb5d0cf31, 0x2cd99e8b, 0x5bdeae1d,
    
79.         0x9b64c2b0, 0xec63f226, 0x756aa39c, 0x026d930a, 0x9c0906a9, 0xeb0e363f,
    
80.         0x72076785, 0x05005713, 0x95bf4a82, 0xe2b87a14, 0x7bb12bae, 0x0cb61b38,
    
81.         0x92d28e9b, 0xe5d5be0d, 0x7cdcefb7, 0x0bdbdf21, 0x86d3d2d4, 0xf1d4e242,
    
82.         0x68ddb3f8, 0x1fda836e, 0x81be16cd, 0xf6b9265b, 0x6fb077e1, 0x18b74777,
    
83.         0x88085ae6, 0xff0f6a70, 0x66063bca, 0x11010b5c, 0x8f659eff, 0xf862ae69,
    
84.         0x616bffd3, 0x166ccf45, 0xa00ae278, 0xd70dd2ee, 0x4e048354, 0x3903b3c2,
    
85.         0xa7672661, 0xd06016f7, 0x4969474d, 0x3e6e77db, 0xaed16a4a, 0xd9d65adc,
    
86.         0x40df0b66, 0x37d83bf0, 0xa9bcae53, 0xdebb9ec5, 0x47b2cf7f, 0x30b5ffe9,
    
87.         0xbdbdf21c, 0xcabac28a, 0x53b39330, 0x24b4a3a6, 0xbad03605, 0xcdd70693,
    
88.         0x54de5729, 0x23d967bf, 0xb3667a2e, 0xc4614ab8, 0x5d681b02, 0x2a6f2b94,
    
89.         0xb40bbe37, 0xc30c8ea1, 0x5a05df1b, 0x2d02ef8d
    
90. };
    
91. 
    
92. uint32_t
    
93. crc32(uint32_t crc, const void *buf, size_t size)
    
94. {
    
95.         const uint8_t *p;
    
96. 
    
97.         p = buf;
    
98.         crc = crc ^ ~0U;
    
99. 
    
100.         while (size--)
     
101.                 crc = crc32_tab[(crc ^ *p++) & 0xFF] ^ (crc >> 8);
     
102. 
     
103.         return crc ^ ~0U;
     
104. }

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link http://opensource.apple.com//source/xnu/xnu-1456.1.26/bsd/libkern/crc32.c