external/public-domain/xz/dist/src/liblzma/check/crc64_fast.c

   1 ///////////////////////////////////////////////////////////////////////////////
   2 //
   3 /// \file       crc64.c
   4 /// \brief      CRC64 calculation
   5 ///
   6 /// Calculate the CRC64 using the slice-by-four algorithm. This is the same
   7 /// idea that is used in crc32_fast.c, but for CRC64 we use only four tables
   8 /// instead of eight to avoid increasing CPU cache usage.
   9 //
  10 //  Author:     Lasse Collin
  11 //
  12 //  This file has been put into the public domain.
  13 //  You can do whatever you want with this file.
  14 //
  15 ///////////////////////////////////////////////////////////////////////////////
  16
  17 #include "check.h"
  18 #include "crc_macros.h"
  19
  20
  21 #ifdef WORDS_BIGENDIAN
  22 #       define A1(x) ((x) >> 56)
  23 #else
  24 #       define A1 A
  25 #endif
  26
  27
  28 // See the comments in crc32_fast.c. They aren't duplicated here.
  29 extern LZMA_API(uint64_t)
  30 lzma_crc64(const uint8_t *buf, size_t size, uint64_t crc)
  31 {
  32         crc = ~crc;
  33
  34 #ifdef WORDS_BIGENDIAN
  35         crc = bswap64(crc);
  36 #endif
  37
  38         if (size > 4) {
  39                 while ((uintptr_t)(buf) & 3) {
  40                         crc = lzma_crc64_table[0][*buf++ ^ A1(crc)] ^ S8(crc);
  41                         --size;
  42                 }
  43
  44                 const uint8_t *const limit = buf + (size & ~(size_t)(3));
  45                 size &= (size_t)(3);
  46
  47                 while (buf < limit) {
  48 #ifdef WORDS_BIGENDIAN
  49                         const uint32_t tmp = (crc >> 32)
  50                                         ^ *(const uint32_t *)(buf);
  51 #else
  52                         const uint32_t tmp = crc ^ *(const uint32_t *)(buf);
  53 #endif
  54                         buf += 4;
  55
  56                         crc = lzma_crc64_table[3][A(tmp)]
  57                             ^ lzma_crc64_table[2][B(tmp)]
  58                             ^ S32(crc)
  59                             ^ lzma_crc64_table[1][C(tmp)]
  60                             ^ lzma_crc64_table[0][D(tmp)];
  61                 }
  62         }
  63
  64         while (size-- != 0)
  65                 crc = lzma_crc64_table[0][*buf++ ^ A1(crc)] ^ S8(crc);
  66
  67 #ifdef WORDS_BIGENDIAN
  68         crc = bswap64(crc);
  69 #endif
  70
  71         return ~crc;
  72 }