The Tor Browser: other-licenses/7zstub/src/Common/CRC.cpp@925c144e1f1f

     1 // Common/CRC.cpp

     3 #include "StdAfx.h"

     5 #include "CRC.h"

     7 static const UInt32 kCRCPoly = 0xEDB88320;

     9 UInt32 CCRC::Table[256];

    11 void CCRC::InitTable()

    12 {

    13   for (UInt32 i = 0; i < 256; i++)

    14   {

    15     UInt32 r = i;

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

    17       if (r & 1)

    18         r = (r >> 1) ^ kCRCPoly;

    19       else

    20         r >>= 1;

    21     CCRC::Table[i] = r;

    22   }

    23 }

    25 class CCRCTableInit

    26 {

    27 public:

    28   CCRCTableInit() { CCRC::InitTable(); }

    29 } g_CRCTableInit;

    31 void CCRC::UpdateByte(Byte b)

    32 {

    33   _value = Table[((Byte)(_value)) ^ b] ^ (_value >> 8);

    34 }

    36 void CCRC::UpdateUInt16(UInt16 v)

    37 {

    38   UpdateByte(Byte(v));

    39   UpdateByte(Byte(v >> 8));

    40 }

    42 void CCRC::UpdateUInt32(UInt32 v)

    43 {

    44   for (int i = 0; i < 4; i++)

    45     UpdateByte((Byte)(v >> (8 * i)));

    46 }

    48 void CCRC::UpdateUInt64(UInt64 v)

    49 {

    50   for (int i = 0; i < 8; i++)

    51     UpdateByte((Byte)(v >> (8 * i)));

    52 }

    54 void CCRC::Update(const void *data, size_t size)

    55 {

    56   UInt32 v = _value;

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

    58   for (; size > 0 ; size--, p++)

    59     v = Table[((Byte)(v)) ^ *p] ^ (v >> 8);

    60   _value = v;

    61 }

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