third_party/lzma_sdk/7zCrcOpt.c

   1 /* 7zCrcOpt.c -- CRC32 calculation : optimized version
   2 2009-11-23 : Igor Pavlov : Public domain */
   3
   4 #include "CpuArch.h"
   5
   6 #ifdef MY_CPU_LE
   7
   8 #define CRC_UPDATE_BYTE_2(crc, b) (table[((crc) ^ (b)) & 0xFF] ^ ((crc) >> 8))
   9
  10 UInt32 MY_FAST_CALL CrcUpdateT4(UInt32 v, const void *data, size_t size, const UInt32 *table)
  11 {
  12   const Byte *p = (const Byte *)data;
  13   for (; size > 0 && ((unsigned)(ptrdiff_t)p & 3) != 0; size--, p++)
  14     v = CRC_UPDATE_BYTE_2(v, *p);
  15   for (; size >= 4; size -= 4, p += 4)
  16   {
  17     v ^= *(const UInt32 *)p;
  18     v =
  19       table[0x300 + (v & 0xFF)] ^
  20       table[0x200 + ((v >> 8) & 0xFF)] ^
  21       table[0x100 + ((v >> 16) & 0xFF)] ^
  22       table[0x000 + ((v >> 24))];
  23   }
  24   for (; size > 0; size--, p++)
  25     v = CRC_UPDATE_BYTE_2(v, *p);
  26   return v;
  27 }
  28
  29 UInt32 MY_FAST_CALL CrcUpdateT8(UInt32 v, const void *data, size_t size, const UInt32 *table)
  30 {
  31   return CrcUpdateT4(v, data, size, table);
  32 }
  33
  34 #endif