1/* 7zCrc.c -- CRC32 init
 22013-11-12 : Igor Pavlov : Public domain */
 3
 4#include "Precomp.h"
 5
 6#include "7zCrc.h"
 7#include "CpuArch.h"
 8
 9#define kCrcPoly 0xEDB88320
10
11#ifdef MY_CPU_X86_OR_AMD64
12  #define CRC_NUM_TABLES 8
13  UInt32 MY_FAST_CALL CrcUpdateT8(UInt32 v, const void *data, size_t size, const UInt32 *table);
14#elif defined(MY_CPU_LE)
15  #define CRC_NUM_TABLES 4
16#else
17  #define CRC_NUM_TABLES 5
18  #define CRC_UINT32_SWAP(v) ((v >> 24) | ((v >> 8) & 0xFF00) | ((v << 8) & 0xFF0000) | (v << 24))
19  UInt32 MY_FAST_CALL CrcUpdateT1_BeT4(UInt32 v, const void *data, size_t size, const UInt32 *table);
20#endif
21
22#ifndef MY_CPU_BE
23  UInt32 MY_FAST_CALL CrcUpdateT4(UInt32 v, const void *data, size_t size, const UInt32 *table);
24#endif
25
26typedef UInt32 (MY_FAST_CALL *CRC_FUNC)(UInt32 v, const void *data, size_t size, const UInt32 *table);
27
28CRC_FUNC g_CrcUpdate;
29UInt32 g_CrcTable[256 * CRC_NUM_TABLES];
30
31UInt32 MY_FAST_CALL CrcUpdate(UInt32 v, const void *data, size_t size)
32{
33  return g_CrcUpdate(v, data, size, g_CrcTable);
34}
35
36UInt32 MY_FAST_CALL CrcCalc(const void *data, size_t size)
37{
38  return g_CrcUpdate(CRC_INIT_VAL, data, size, g_CrcTable) ^ CRC_INIT_VAL;
39}
40
41void MY_FAST_CALL CrcGenerateTable()
42{
43  UInt32 i;
44  for (i = 0; i < 256; i++)
45  {
46    UInt32 r = i;
47    unsigned j;
48    for (j = 0; j < 8; j++)
49      r = (r >> 1) ^ (kCrcPoly & ~((r & 1) - 1));
50    g_CrcTable[i] = r;
51  }
52  for (; i < 256 * CRC_NUM_TABLES; i++)
53  {
54    UInt32 r = g_CrcTable[i - 256];
55    g_CrcTable[i] = g_CrcTable[r & 0xFF] ^ (r >> 8);
56  }
57  
58  #ifdef MY_CPU_LE
59
60  g_CrcUpdate = CrcUpdateT4;
61  
62  #if CRC_NUM_TABLES == 8
63  if (!CPU_Is_InOrder())
64    g_CrcUpdate = CrcUpdateT8;
65  #endif
66
67  #else
68  {
69    #ifndef MY_CPU_BE
70    UInt32 k = 1;
71    if (*(const Byte *)&k == 1)
72      g_CrcUpdate = CrcUpdateT4;
73    else
74    #endif
75    {
76      for (i = 256 * CRC_NUM_TABLES - 1; i >= 256; i--)
77      {
78        UInt32 x = g_CrcTable[i - 256];
79        g_CrcTable[i] = CRC_UINT32_SWAP(x);
80      }
81      g_CrcUpdate = CrcUpdateT1_BeT4;
82    }
83  }
84  #endif
85}