73 lines
1.8 KiB
C++
Executable File
73 lines
1.8 KiB
C++
Executable File
//-----------------------------------------------------------------------------
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// Torque Game Engine
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// Copyright (C) GarageGames.com, Inc.
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//-----------------------------------------------------------------------------
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#include "platform/platform.h"
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#include "core/stream.h"
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//-----------------------------------------------------------------------------
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// simple crc function - generates lookup table on first call
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static U32 crcTable[256];
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static bool crcTableValid;
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static void calculateCRCTable()
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{
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U32 val;
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for(S32 i = 0; i < 256; i++)
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{
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val = i;
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for(S32 j = 0; j < 8; j++)
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{
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if(val & 0x01)
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val = 0xedb88320 ^ (val >> 1);
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else
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val = val >> 1;
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}
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crcTable[i] = val;
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}
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crcTableValid = true;
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}
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//-----------------------------------------------------------------------------
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U32 calculateCRC(const void * buffer, S32 len, U32 crcVal )
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{
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// check if need to generate the crc table
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if(!crcTableValid)
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calculateCRCTable();
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// now calculate the crc
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char * buf = (char*)buffer;
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for(S32 i = 0; i < len; i++)
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crcVal = crcTable[(crcVal ^ buf[i]) & 0xff] ^ (crcVal >> 8);
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return(crcVal);
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}
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U32 calculateCRCStream(Stream *stream, U32 crcVal )
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{
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// check if need to generate the crc table
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if(!crcTableValid)
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calculateCRCTable();
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// now calculate the crc
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stream->setPosition(0);
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S32 len = stream->getStreamSize();
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U8 buf[4096];
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S32 segCount = (len + 4095) / 4096;
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for(S32 j = 0; j < segCount; j++)
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{
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S32 slen = getMin(4096, len - (j * 4096));
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stream->read(slen, buf);
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crcVal = calculateCRC(buf, slen, crcVal);
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}
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stream->setPosition(0);
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return(crcVal);
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}
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