sys/libkern/crc32.c

   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  * CRC32 code derived from work by Gary S. Brown.
  40  *
  41  * $FreeBSD: src/sys/libkern/crc32.c,v 1.1.2.1 2002/07/31 09:08:34 imp Exp $
  42  * $DragonFly: src/sys/libkern/crc32.c,v 1.7 2008/11/03 08:41:31 swildner Exp $
  43  */
  44
  45 /*
  46  * WARNING: This code is used by various subsystems including the HAMMER
  47  * filesystem.  This code may be directly compiled in userland or kernel
  48  * builds.
  49  */
  50
  51 #ifdef _KERNEL
  52 #include <sys/param.h>
  53 #include <sys/systm.h>
  54 #else
  55 #include <sys/types.h>
  56 #endif
  57
  58 #ifndef _KERNEL
  59 /* prototypes for the kernel are in <sys/systm.h> */
  60 extern const uint32_t crc32_tab[];
  61 uint32_t crc32(const void *buf, size_t size);
  62 uint32_t crc32_ext(const void *buf, size_t size, uint32_t ocrc);
  63 #endif
  64
  65 #if 0
  66 /* see icrc32.c */
  67 const uint32_t crc32_tab[] = {
  68         0x00000000, 0x77073096, 0xee0e612c, 0x990951ba, 0x076dc419, 0x706af48f,
  69         0xe963a535, 0x9e6495a3, 0x0edb8832, 0x79dcb8a4, 0xe0d5e91e, 0x97d2d988,
  70         0x09b64c2b, 0x7eb17cbd, 0xe7b82d07, 0x90bf1d91, 0x1db71064, 0x6ab020f2,
  71         0xf3b97148, 0x84be41de, 0x1adad47d, 0x6ddde4eb, 0xf4d4b551, 0x83d385c7,
  72         0x136c9856, 0x646ba8c0, 0xfd62f97a, 0x8a65c9ec, 0x14015c4f, 0x63066cd9,
  73         0xfa0f3d63, 0x8d080df5, 0x3b6e20c8, 0x4c69105e, 0xd56041e4, 0xa2677172,
  74         0x3c03e4d1, 0x4b04d447, 0xd20d85fd, 0xa50ab56b, 0x35b5a8fa, 0x42b2986c,
  75         0xdbbbc9d6, 0xacbcf940, 0x32d86ce3, 0x45df5c75, 0xdcd60dcf, 0xabd13d59,
  76         0x26d930ac, 0x51de003a, 0xc8d75180, 0xbfd06116, 0x21b4f4b5, 0x56b3c423,
  77         0xcfba9599, 0xb8bda50f, 0x2802b89e, 0x5f058808, 0xc60cd9b2, 0xb10be924,
  78         0x2f6f7c87, 0x58684c11, 0xc1611dab, 0xb6662d3d, 0x76dc4190, 0x01db7106,
  79         0x98d220bc, 0xefd5102a, 0x71b18589, 0x06b6b51f, 0x9fbfe4a5, 0xe8b8d433,
  80         0x7807c9a2, 0x0f00f934, 0x9609a88e, 0xe10e9818, 0x7f6a0dbb, 0x086d3d2d,
  81         0x91646c97, 0xe6635c01, 0x6b6b51f4, 0x1c6c6162, 0x856530d8, 0xf262004e,
  82         0x6c0695ed, 0x1b01a57b, 0x8208f4c1, 0xf50fc457, 0x65b0d9c6, 0x12b7e950,
  83         0x8bbeb8ea, 0xfcb9887c, 0x62dd1ddf, 0x15da2d49, 0x8cd37cf3, 0xfbd44c65,
  84         0x4db26158, 0x3ab551ce, 0xa3bc0074, 0xd4bb30e2, 0x4adfa541, 0x3dd895d7,
  85         0xa4d1c46d, 0xd3d6f4fb, 0x4369e96a, 0x346ed9fc, 0xad678846, 0xda60b8d0,
  86         0x44042d73, 0x33031de5, 0xaa0a4c5f, 0xdd0d7cc9, 0x5005713c, 0x270241aa,
  87         0xbe0b1010, 0xc90c2086, 0x5768b525, 0x206f85b3, 0xb966d409, 0xce61e49f,
  88         0x5edef90e, 0x29d9c998, 0xb0d09822, 0xc7d7a8b4, 0x59b33d17, 0x2eb40d81,
  89         0xb7bd5c3b, 0xc0ba6cad, 0xedb88320, 0x9abfb3b6, 0x03b6e20c, 0x74b1d29a,
  90         0xead54739, 0x9dd277af, 0x04db2615, 0x73dc1683, 0xe3630b12, 0x94643b84,
  91         0x0d6d6a3e, 0x7a6a5aa8, 0xe40ecf0b, 0x9309ff9d, 0x0a00ae27, 0x7d079eb1,
  92         0xf00f9344, 0x8708a3d2, 0x1e01f268, 0x6906c2fe, 0xf762575d, 0x806567cb,
  93         0x196c3671, 0x6e6b06e7, 0xfed41b76, 0x89d32be0, 0x10da7a5a, 0x67dd4acc,
  94         0xf9b9df6f, 0x8ebeeff9, 0x17b7be43, 0x60b08ed5, 0xd6d6a3e8, 0xa1d1937e,
  95         0x38d8c2c4, 0x4fdff252, 0xd1bb67f1, 0xa6bc5767, 0x3fb506dd, 0x48b2364b,
  96         0xd80d2bda, 0xaf0a1b4c, 0x36034af6, 0x41047a60, 0xdf60efc3, 0xa867df55,
  97         0x316e8eef, 0x4669be79, 0xcb61b38c, 0xbc66831a, 0x256fd2a0, 0x5268e236,
  98         0xcc0c7795, 0xbb0b4703, 0x220216b9, 0x5505262f, 0xc5ba3bbe, 0xb2bd0b28,
  99         0x2bb45a92, 0x5cb36a04, 0xc2d7ffa7, 0xb5d0cf31, 0x2cd99e8b, 0x5bdeae1d,
 100         0x9b64c2b0, 0xec63f226, 0x756aa39c, 0x026d930a, 0x9c0906a9, 0xeb0e363f,
 101         0x72076785, 0x05005713, 0x95bf4a82, 0xe2b87a14, 0x7bb12bae, 0x0cb61b38,
 102         0x92d28e9b, 0xe5d5be0d, 0x7cdcefb7, 0x0bdbdf21, 0x86d3d2d4, 0xf1d4e242,
 103         0x68ddb3f8, 0x1fda836e, 0x81be16cd, 0xf6b9265b, 0x6fb077e1, 0x18b74777,
 104         0x88085ae6, 0xff0f6a70, 0x66063bca, 0x11010b5c, 0x8f659eff, 0xf862ae69,
 105         0x616bffd3, 0x166ccf45, 0xa00ae278, 0xd70dd2ee, 0x4e048354, 0x3903b3c2,
 106         0xa7672661, 0xd06016f7, 0x4969474d, 0x3e6e77db, 0xaed16a4a, 0xd9d65adc,
 107         0x40df0b66, 0x37d83bf0, 0xa9bcae53, 0xdebb9ec5, 0x47b2cf7f, 0x30b5ffe9,
 108         0xbdbdf21c, 0xcabac28a, 0x53b39330, 0x24b4a3a6, 0xbad03605, 0xcdd70693,
 109         0x54de5729, 0x23d967bf, 0xb3667a2e, 0xc4614ab8, 0x5d681b02, 0x2a6f2b94,
 110         0xb40bbe37, 0xc30c8ea1, 0x5a05df1b, 0x2d02ef8d
 111 };
 112 #endif
 113
 114 uint32_t
 115 crc32(const void *buf, size_t size)
 116 {
 117         const uint8_t *p;
 118         uint32_t crc;
 119
 120         p = buf;
 121         crc = ~0U;
 122
 123         while (size--)
 124                 crc = crc32_tab[(crc ^ *p++) & 0xFF] ^ (crc >> 8);
 125
 126         return crc ^ ~0U;
 127 }
 128
 129 uint32_t
 130 crc32_ext(const void *buf, size_t size, uint32_t ocrc)
 131 {
 132         const uint8_t *p;
 133         uint32_t crc;
 134
 135         p = buf;
 136         crc = ~ocrc;
 137
 138         while (size--)
 139                 crc = crc32_tab[(crc ^ *p++) & 0xFF] ^ (crc >> 8);
 140
 141         return crc ^ ~0U;
 142 }
 143