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
CrcUpdateT1(UInt32 v,const void * data,size_t size,const UInt32 * table)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
CrcUpdate(UInt32 v,const void * data,size_t size)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
CrcCalc(const void * data,size_t size)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
CrcGenerateTable()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 }
75