/* 7zCrc.c -- CRC32 init

2017-06-06 : Igor Pavlov : Public domain */

#include "Precomp.h"

#include "7zCrc.h"

#include "CpuArch.h"

#define kCrcPoly 0xEDB88320

#ifdef MY_CPU_LE

  #define CRC_NUM_TABLES 8

#else

  #define CRC_NUM_TABLES 9

  #define CRC_UINT32_SWAP(v) ((v >> 24) | ((v >> 8) & 0xFF00) | ((v << 8) & 0xFF0000) | (v << 24))

  UInt32 MY_FAST_CALL CrcUpdateT1_BeT4(UInt32 v, const void *data, size_t size, const UInt32 *table);

  UInt32 MY_FAST_CALL CrcUpdateT1_BeT8(UInt32 v, const void *data, size_t size, const UInt32 *table);

#endif

#ifndef MY_CPU_BE

  UInt32 MY_FAST_CALL CrcUpdateT4(UInt32 v, const void *data, size_t size, const UInt32 *table);

  UInt32 MY_FAST_CALL CrcUpdateT8(UInt32 v, const void *data, size_t size, const UInt32 *table);

#endif

typedef UInt32 (MY_FAST_CALL *CRC_FUNC)(UInt32 v, const void *data, size_t size, const UInt32 *table);

CRC_FUNC g_CrcUpdateT4;

CRC_FUNC g_CrcUpdateT8;

CRC_FUNC g_CrcUpdate;

UInt32 g_CrcTable[256 * CRC_NUM_TABLES];

UInt32 MY_FAST_CALL CrcUpdate(UInt32 v, const void *data, size_t size)

{

  return g_CrcUpdate(v, data, size, g_CrcTable);

}

UInt32 MY_FAST_CALL CrcCalc(const void *data, size_t size)

{

  return g_CrcUpdate(CRC_INIT_VAL, data, size, g_CrcTable) ^ CRC_INIT_VAL;

}

#define CRC_UPDATE_BYTE_2(crc, b) (table[((crc) ^ (b)) & 0xFF] ^ ((crc) >> 8))

UInt32 MY_FAST_CALL CrcUpdateT1(UInt32 v, const void *data, size_t size, const UInt32 *table)

{

  const Byte *p = (const Byte *)data;

  const Byte *pEnd = p + size;

  for (; p != pEnd; p++)

    v = CRC_UPDATE_BYTE_2(v, *p);

  return v;

}

void MY_FAST_CALL CrcGenerateTable()

{

  UInt32 i;

  for (i = 0; i < 256; i++)

  {

    UInt32 r = i;

    unsigned j;

    for (j = 0; j < 8; j++)

      r = (r >> 1) ^ (kCrcPoly & ((UInt32)0 - (r & 1)));

    g_CrcTable[i] = r;

  }

  for (i = 256; i < 256 * CRC_NUM_TABLES; i++)

  {

    UInt32 r = g_CrcTable[(size_t)i - 256];

    g_CrcTable[i] = g_CrcTable[r & 0xFF] ^ (r >> 8);

  }

  #if CRC_NUM_TABLES < 4

  g_CrcUpdate = CrcUpdateT1;

  #else

  #ifdef MY_CPU_LE

    g_CrcUpdateT4 = CrcUpdateT4;

    g_CrcUpdate = CrcUpdateT4;

    #if CRC_NUM_TABLES >= 8

      g_CrcUpdateT8 = CrcUpdateT8;

      #ifdef MY_CPU_X86_OR_AMD64

      if (!CPU_Is_InOrder())

      #endif

        g_CrcUpdate = CrcUpdateT8;

    #endif

  #else

  {

    #ifndef MY_CPU_BE

    UInt32 k = 0x01020304;

    const Byte *p = (const Byte *)&k;

    if (p[0] == 4 && p[1] == 3)

    {

      g_CrcUpdateT4 = CrcUpdateT4;

      g_CrcUpdate = CrcUpdateT4;

      #if CRC_NUM_TABLES >= 8

      g_CrcUpdateT8 = CrcUpdateT8;

      g_CrcUpdate = CrcUpdateT8;

      #endif

    }

    else if (p[0] != 1 || p[1] != 2)

      g_CrcUpdate = CrcUpdateT1;

    else

    #endif

    {

      for (i = 256 * CRC_NUM_TABLES - 1; i >= 256; i--)

      {

        UInt32 x = g_CrcTable[(size_t)i - 256];

        g_CrcTable[i] = CRC_UINT32_SWAP(x);

      }

      g_CrcUpdateT4 = CrcUpdateT1_BeT4;

      g_CrcUpdate = CrcUpdateT1_BeT4;

      #if CRC_NUM_TABLES >= 8

      g_CrcUpdateT8 = CrcUpdateT1_BeT8;

      g_CrcUpdate = CrcUpdateT1_BeT8;

      #endif

    }

  }

  #endif

  #endif

}