1/* 7zCrc.c -- CRC32 calculation
22009-11-23 : 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
15typedef UInt32 (MY_FAST_CALL *CRC_FUNC)(UInt32 v, const void *data, size_t size, const UInt32 *table);
16
17static CRC_FUNC g_CrcUpdate;
18UInt32 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
24static 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
34UInt32 MY_FAST_CALL CrcUpdateT4(UInt32 v, const void *data, size_t size, const UInt32 *table);
35UInt32 MY_FAST_CALL CrcUpdateT8(UInt32 v, const void *data, size_t size, const UInt32 *table);
36
37#endif
38
39UInt32 MY_FAST_CALL CrcUpdate(UInt32 v, const void *data, size_t size)
40{
41  return g_CrcUpdate(v, data, size, g_CrcTable);
42}
43
44UInt32 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
49void 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}
75