125 lines
3.6 KiB
C++
125 lines
3.6 KiB
C++
/****************************************************************************
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Copyright (c) 2006, Radon Labs GmbH
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Copyright (c) 2011-2013,WebJet Business Division,CYOU
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http://www.genesis-3d.com.cn
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Permission is hereby granted, free of charge, to any person obtaining a copy
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of this software and associated documentation files (the "Software"), to deal
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in the Software without restriction, including without limitation the rights
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to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
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copies of the Software, and to permit persons to whom the Software is
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furnished to do so, subject to the following conditions:
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The above copyright notice and this permission notice shall be included in
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all copies or substantial portions of the Software.
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THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
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IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
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FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
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AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
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LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
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OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
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THE SOFTWARE.
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****************************************************************************/
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#include "stdneb.h"
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#include "util/crc.h"
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namespace Util
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{
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unsigned int Crc::Table[NumByteValues] = { 0 };
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bool Crc::TableInitialized = false;
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//------------------------------------------------------------------------------
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/**
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*/
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Crc::Crc() :
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inBegin(false),
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resultValid(false),
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checksum(0)
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{
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// first-time byte table initialization
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if (!TableInitialized)
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{
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unsigned int i;
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for (i = 0; i < NumByteValues; ++i)
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{
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unsigned int reg = i << 24;
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int j;
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for (j = 0; j < 8; ++j)
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{
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bool topBit = (reg & 0x80000000) != 0;
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reg <<= 1;
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if (topBit)
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{
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reg ^= Key;
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}
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}
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Table[i] = reg;
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}
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TableInitialized = true;
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}
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}
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//------------------------------------------------------------------------------
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/**
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Begin computing a CRC checksum over several chunks of data. This can be
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done in multiple runs, which is the only useful way to compute
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checksum for large files.
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*/
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void
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Crc::Begin()
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{
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n_assert(!this->inBegin);
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this->resultValid = false;
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this->inBegin = true;
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this->checksum = 0;
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}
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//------------------------------------------------------------------------------
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/**
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Do one run of checksum computation for a chunk of data. Must be
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executed inside Begin()/End().
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*/
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void
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Crc::Compute(unsigned char* buf, unsigned int numBytes)
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{
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n_assert(this->inBegin);
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unsigned int i;
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for (i = 0; i < numBytes; i++)
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{
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uint top = this->checksum >> 24;
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top ^= buf[i];
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this->checksum = (this->checksum << 8) ^ Table[top];
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}
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}
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//------------------------------------------------------------------------------
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/**
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End checksum computation. This validates the result, so that
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it can be accessed with GetResult().
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*/
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void
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Crc::End()
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{
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n_assert(this->inBegin);
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this->inBegin = false;
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this->resultValid = true;
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}
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//------------------------------------------------------------------------------
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/**
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Get the result of the checksum computation. Must be executed
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after End().
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*/
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unsigned int
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Crc::GetResult() const
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{
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n_assert(!this->inBegin);
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n_assert(this->resultValid);
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return this->checksum;
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}
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} // namespace Util
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