third_party/lzma_sdk/7zCrc.c

   1 /* 7zCrc.c -- CRC32 calculation
   2 2009-11-23 : Igor Pavlov : Public domain */
   3
   4 #include "7zCrc.h"
   5 #include "CpuArch.h"
   6
   7 #define kCrcPoly 0xEDB88320
   8
   9 #ifdef MY_CPU_LE
  10 #define CRC_NUM_TABLES 8
  11 #else
  12 #define CRC_NUM_TABLES 1
  13 #endif
  14
  15 typedef UInt32 (MY_FAST_CALL *CRC_FUNC)(UInt32 v, const void *data, size_t size, const UInt32 *table);
  16
  17 static CRC_FUNC g_CrcUpdate;
  18 UInt32 g_CrcTable[256 * CRC_NUM_TABLES];
  19
  20 #if CRC_NUM_TABLES == 1
  21
  22 #define CRC_UPDATE_BYTE_2(crc, b) (table[((crc) ^ (b)) & 0xFF] ^ ((crc) >> 8))
  23
  24 static UInt32 MY_FAST_CALL CrcUpdateT1(UInt32 v, const void *data, size_t size, const UInt32 *table)
  25 {
  26   const Byte *p = (const Byte *)data;
  27   for (; size > 0; size--, p++)
  28     v = CRC_UPDATE_BYTE_2(v, *p);
  29   return v;
  30 }
  31
  32 #else
  33
  34 UInt32 MY_FAST_CALL CrcUpdateT4(UInt32 v, const void *data, size_t size, const UInt32 *table);
  35 UInt32 MY_FAST_CALL CrcUpdateT8(UInt32 v, const void *data, size_t size, const UInt32 *table);
  36
  37 #endif
  38
  39 UInt32 MY_FAST_CALL CrcUpdate(UInt32 v, const void *data, size_t size)
  40 {
  41   return g_CrcUpdate(v, data, size, g_CrcTable);
  42 }
  43
  44 UInt32 MY_FAST_CALL CrcCalc(const void *data, size_t size)
  45 {
  46   return g_CrcUpdate(CRC_INIT_VAL, data, size, g_CrcTable) ^ CRC_INIT_VAL;
  47 }
  48
  49 void MY_FAST_CALL CrcGenerateTable()
  50 {
  51   UInt32 i;
  52   for (i = 0; i < 256; i++)
  53   {
  54     UInt32 r = i;
  55     unsigned j;
  56     for (j = 0; j < 8; j++)
  57       r = (r >> 1) ^ (kCrcPoly & ~((r & 1) - 1));
  58     g_CrcTable[i] = r;
  59   }
  60   #if CRC_NUM_TABLES == 1
  61   g_CrcUpdate = CrcUpdateT1;
  62   #else
  63   for (; i < 256 * CRC_NUM_TABLES; i++)
  64   {
  65     UInt32 r = g_CrcTable[i - 256];
  66     g_CrcTable[i] = g_CrcTable[r & 0xFF] ^ (r >> 8);
  67   }
  68   g_CrcUpdate = CrcUpdateT4;
  69   #ifdef MY_CPU_X86_OR_AMD64
  70   if (!CPU_Is_InOrder())
  71     g_CrcUpdate = CrcUpdateT8;
  72   #endif
  73   #endif
  74 }