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      1 /* 7zCrc.c -- CRC32 init
      2 2017-06-06 : 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_LE
     12   #define CRC_NUM_TABLES 8
     13 #else
     14   #define CRC_NUM_TABLES 9
     15 
     16   #define CRC_UINT32_SWAP(v) ((v >> 24) | ((v >> 8) & 0xFF00) | ((v << 8) & 0xFF0000) | (v << 24))
     17 
     18   UInt32 MY_FAST_CALL CrcUpdateT1_BeT4(UInt32 v, const void *data, size_t size, const UInt32 *table);
     19   UInt32 MY_FAST_CALL CrcUpdateT1_BeT8(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   UInt32 MY_FAST_CALL CrcUpdateT8(UInt32 v, const void *data, size_t size, const UInt32 *table);
     25 #endif
     26 
     27 typedef UInt32 (MY_FAST_CALL *CRC_FUNC)(UInt32 v, const void *data, size_t size, const UInt32 *table);
     28 
     29 CRC_FUNC g_CrcUpdateT4;
     30 CRC_FUNC g_CrcUpdateT8;
     31 CRC_FUNC g_CrcUpdate;
     32 
     33 UInt32 g_CrcTable[256 * CRC_NUM_TABLES];
     34 
     35 UInt32 MY_FAST_CALL CrcUpdate(UInt32 v, const void *data, size_t size)
     36 {
     37   return g_CrcUpdate(v, data, size, g_CrcTable);
     38 }
     39 
     40 UInt32 MY_FAST_CALL CrcCalc(const void *data, size_t size)
     41 {
     42   return g_CrcUpdate(CRC_INIT_VAL, data, size, g_CrcTable) ^ CRC_INIT_VAL;
     43 }
     44 
     45 #define CRC_UPDATE_BYTE_2(crc, b) (table[((crc) ^ (b)) & 0xFF] ^ ((crc) >> 8))
     46 
     47 UInt32 MY_FAST_CALL CrcUpdateT1(UInt32 v, const void *data, size_t size, const UInt32 *table)
     48 {
     49   const Byte *p = (const Byte *)data;
     50   const Byte *pEnd = p + size;
     51   for (; p != pEnd; p++)
     52     v = CRC_UPDATE_BYTE_2(v, *p);
     53   return v;
     54 }
     55 
     56 void MY_FAST_CALL CrcGenerateTable()
     57 {
     58   UInt32 i;
     59   for (i = 0; i < 256; i++)
     60   {
     61     UInt32 r = i;
     62     unsigned j;
     63     for (j = 0; j < 8; j++)
     64       r = (r >> 1) ^ (kCrcPoly & ((UInt32)0 - (r & 1)));
     65     g_CrcTable[i] = r;
     66   }
     67   for (i = 256; i < 256 * CRC_NUM_TABLES; i++)
     68   {
     69     UInt32 r = g_CrcTable[(size_t)i - 256];
     70     g_CrcTable[i] = g_CrcTable[r & 0xFF] ^ (r >> 8);
     71   }
     72 
     73   #if CRC_NUM_TABLES < 4
     74 
     75   g_CrcUpdate = CrcUpdateT1;
     76 
     77   #else
     78 
     79   #ifdef MY_CPU_LE
     80 
     81     g_CrcUpdateT4 = CrcUpdateT4;
     82     g_CrcUpdate = CrcUpdateT4;
     83 
     84     #if CRC_NUM_TABLES >= 8
     85       g_CrcUpdateT8 = CrcUpdateT8;
     86 
     87       #ifdef MY_CPU_X86_OR_AMD64
     88       if (!CPU_Is_InOrder())
     89       #endif
     90         g_CrcUpdate = CrcUpdateT8;
     91     #endif
     92 
     93   #else
     94   {
     95     #ifndef MY_CPU_BE
     96     UInt32 k = 0x01020304;
     97     const Byte *p = (const Byte *)&k;
     98     if (p[0] == 4 && p[1] == 3)
     99     {
    100       g_CrcUpdateT4 = CrcUpdateT4;
    101       g_CrcUpdate = CrcUpdateT4;
    102       #if CRC_NUM_TABLES >= 8
    103       g_CrcUpdateT8 = CrcUpdateT8;
    104       g_CrcUpdate = CrcUpdateT8;
    105       #endif
    106     }
    107     else if (p[0] != 1 || p[1] != 2)
    108       g_CrcUpdate = CrcUpdateT1;
    109     else
    110     #endif
    111     {
    112       for (i = 256 * CRC_NUM_TABLES - 1; i >= 256; i--)
    113       {
    114         UInt32 x = g_CrcTable[(size_t)i - 256];
    115         g_CrcTable[i] = CRC_UINT32_SWAP(x);
    116       }
    117       g_CrcUpdateT4 = CrcUpdateT1_BeT4;
    118       g_CrcUpdate = CrcUpdateT1_BeT4;
    119       #if CRC_NUM_TABLES >= 8
    120       g_CrcUpdateT8 = CrcUpdateT1_BeT8;
    121       g_CrcUpdate = CrcUpdateT1_BeT8;
    122       #endif
    123     }
    124   }
    125   #endif
    126 
    127   #endif
    128 }
    129