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91 lines
2.3 KiB
91 lines
2.3 KiB
5 years ago
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// zlib.cpp - written and placed in the public domain by Wei Dai
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// "zlib" is the name of a well known C language compression library
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// (http://www.zlib.org) and also the name of a compression format
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// (RFC 1950) that the library implements. This file is part of a
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// complete reimplementation of the zlib compression format.
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#include "pch.h"
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#include "zlib.h"
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#include "zdeflate.h"
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#include "zinflate.h"
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NAMESPACE_BEGIN(CryptoPP)
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static const byte DEFLATE_METHOD = 8;
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static const byte FDICT_FLAG = 1 << 5;
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// *************************************************************
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void ZlibCompressor::WritePrestreamHeader()
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{
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m_adler32.Restart();
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byte cmf = DEFLATE_METHOD | ((GetLog2WindowSize()-8) << 4);
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byte flags = GetCompressionLevel() << 6;
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AttachedTransformation()->PutWord16(RoundUpToMultipleOf(cmf*256+flags, 31));
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}
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void ZlibCompressor::ProcessUncompressedData(const byte *inString, size_t length)
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{
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m_adler32.Update(inString, length);
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}
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void ZlibCompressor::WritePoststreamTail()
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{
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FixedSizeSecBlock<byte, 4> adler32;
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m_adler32.Final(adler32);
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AttachedTransformation()->Put(adler32, 4);
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}
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unsigned int ZlibCompressor::GetCompressionLevel() const
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{
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static const unsigned int deflateToCompressionLevel[] = {0, 1, 1, 1, 2, 2, 2, 2, 2, 3};
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return deflateToCompressionLevel[GetDeflateLevel()];
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}
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// *************************************************************
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ZlibDecompressor::ZlibDecompressor(BufferedTransformation *attachment, bool repeat, int propagation)
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: Inflator(attachment, repeat, propagation)
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{
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}
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void ZlibDecompressor::ProcessPrestreamHeader()
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{
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m_adler32.Restart();
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byte cmf;
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byte flags;
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if (!m_inQueue.Get(cmf) || !m_inQueue.Get(flags))
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throw HeaderErr();
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if ((cmf*256+flags) % 31 != 0)
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throw HeaderErr(); // if you hit this exception, you're probably trying to decompress invalid data
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if ((cmf & 0xf) != DEFLATE_METHOD)
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throw UnsupportedAlgorithm();
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if (flags & FDICT_FLAG)
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throw UnsupportedPresetDictionary();
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m_log2WindowSize = 8 + (cmf >> 4);
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}
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void ZlibDecompressor::ProcessDecompressedData(const byte *inString, size_t length)
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{
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AttachedTransformation()->Put(inString, length);
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m_adler32.Update(inString, length);
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}
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void ZlibDecompressor::ProcessPoststreamTail()
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{
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FixedSizeSecBlock<byte, 4> adler32;
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if (m_inQueue.Get(adler32, 4) != 4)
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throw Adler32Err();
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if (!m_adler32.Verify(adler32))
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throw Adler32Err();
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}
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NAMESPACE_END
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