crc32c.c

   1 /*
   2  * Oct 28, 2015 Song Liu simplified the code and port it to mdadm
   3  *
   4  * Aug 8, 2011 Bob Pearson with help from Joakim Tjernlund and George Spelvin
   5  * cleaned up code to current version of sparse and added the slicing-by-8
   6  * algorithm to the closely similar existing slicing-by-4 algorithm.
   7  *
   8  * Oct 15, 2000 Matt Domsch <Matt_Domsch@dell.com>
   9  * Nicer crc32 functions/docs submitted by linux@horizon.com.  Thanks!
  10  * Code was from the public domain, copyright abandoned.  Code was
  11  * subsequently included in the kernel, thus was re-licensed under the
  12  * GNU GPL v2.
  13  *
  14  * Oct 12, 2000 Matt Domsch <Matt_Domsch@dell.com>
  15  * Same crc32 function was used in 5 other places in the kernel.
  16  * I made one version, and deleted the others.
  17  * There are various incantations of crc32().  Some use a seed of 0 or ~0.
  18  * Some xor at the end with ~0.  The generic crc32() function takes
  19  * seed as an argument, and doesn't xor at the end.  Then individual
  20  * users can do whatever they need.
  21  *   drivers/net/smc9194.c uses seed ~0, doesn't xor with ~0.
  22  *   fs/jffs2 uses seed 0, doesn't xor with ~0.
  23  *   fs/partitions/efi.c uses seed ~0, xor's with ~0.
  24  *
  25  * This source code is licensed under the GNU General Public License,
  26  * Version 2.  See the file COPYING for more details.
  27  */
  28
  29 #include <sys/types.h>
  30 #include <asm/types.h>
  31 #include <stdlib.h>
  32
  33 /*
  34  * There are multiple 16-bit CRC polynomials in common use, but this is
  35  * *the* standard CRC-32 polynomial, first popularized by Ethernet.
  36  * 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
  37  */
  38 #define CRCPOLY_LE 0xedb88320
  39 #define CRCPOLY_BE 0x04c11db7
  40
  41 /*
  42  * This is the CRC32c polynomial, as outlined by Castagnoli.
  43  * x^32+x^28+x^27+x^26+x^25+x^23+x^22+x^20+x^19+x^18+x^14+x^13+x^11+x^10+x^9+
  44  * x^8+x^6+x^0
  45  */
  46 #define CRC32C_POLY_LE 0x82F63B78
  47
  48 /**
  49  * crc32_le_generic() - Calculate bitwise little-endian Ethernet AUTODIN II
  50  *                      CRC32/CRC32C
  51  * @crc: seed value for computation.  ~0 for Ethernet, sometimes 0 for other
  52  *       uses, or the previous crc32/crc32c value if computing incrementally.
  53  * @p: pointer to buffer over which CRC32/CRC32C is run
  54  * @len: length of buffer @p
  55  * @polynomial: CRC32/CRC32c LE polynomial
  56  */
  57 static inline __u32 crc32_le_generic(__u32 crc, unsigned char const *p,
  58                                      size_t len, __u32 polynomial)
  59 {
  60         int i;
  61         while (len--) {
  62                 crc ^= *p++;
  63                 for (i = 0; i < 8; i++)
  64                         crc = (crc >> 1) ^ ((crc & 1) ? polynomial : 0);
  65         }
  66         return crc;
  67 }
  68
  69 __u32 crc32_le(__u32 crc, unsigned char const *p, size_t len)
  70 {
  71         return crc32_le_generic(crc, p, len, CRCPOLY_LE);
  72 }
  73
  74 __u32 crc32c_le(__u32 crc, unsigned char const *p, size_t len)
  75 {
  76         return crc32_le_generic(crc, p, len, CRC32C_POLY_LE);
  77 }
  78
  79 /**
  80  * crc32_be_generic() - Calculate bitwise big-endian Ethernet AUTODIN II CRC32
  81  * @crc: seed value for computation.  ~0 for Ethernet, sometimes 0 for
  82  *      other uses, or the previous crc32 value if computing incrementally.
  83  * @p: pointer to buffer over which CRC32 is run
  84  * @len: length of buffer @p
  85  * @polynomial: CRC32 BE polynomial
  86  */
  87 static inline __u32 crc32_be_generic(__u32 crc, unsigned char const *p,
  88                                      size_t len, __u32 polynomial)
  89 {
  90         int i;
  91         while (len--) {
  92                 crc ^= *p++ << 24;
  93                 for (i = 0; i < 8; i++)
  94                         crc =
  95                             (crc << 1) ^ ((crc & 0x80000000) ? polynomial :
  96                                           0);
  97         }
  98         return crc;
  99 }
 100
 101 __u32 crc32_be(__u32 crc, unsigned char const *p, size_t len)
 102 {
 103         return crc32_be_generic(crc, p, len, CRCPOLY_BE);
 104 }