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90 lines
2.3 KiB
90 lines
2.3 KiB
// 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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