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# zlib.cpp

    00001 // zlib.cpp - written and placed in the public domain by Wei Dai
    00002
    00003 // "zlib" is the name of a well known C language compression library
    00004 // (http://www.zlib.org) and also the name of a compression format
    00005 // (RFC 1950) that the library implements. This file is part of a
    00006 // complete reimplementation of the zlib compression format.
    00007
    00008 #include "pch.h"
    00009 #include "zlib.h"
    00010 #include "zdeflate.h"
    00011 #include "zinflate.h"
    00012
    00013 NAMESPACE_BEGIN(CryptoPP)
    00014
    00015 static const byte DEFLATE_METHOD = 8;
    00016 static const byte FDICT_FLAG = 1 << 5;
    00017
    00018 // *************************************************************
    00019
    00020 void ZlibCompressor::WritePrestreamHeader()
    00021 {
    00022         m_adler32.Restart();
    00023         byte cmf = DEFLATE_METHOD | ((GetLog2WindowSize()-8) << 4);
    00024         byte flags = GetCompressionLevel() << 6;
    00025         AttachedTransformation()->PutWord16(RoundUpToMultipleOf(cmf*256+flags, 31));
    00026 }
    00027
    00028 void ZlibCompressor::ProcessUncompressedData(const byte *inString, size_t length)
    00029 {
    00030         m_adler32.Update(inString, length);
    00031 }
    00032
    00033 void ZlibCompressor::WritePoststreamTail()
    00034 {
    00035         FixedSizeSecBlock<byte, 4> adler32;
    00036         m_adler32.Final(adler32);
    00037         AttachedTransformation()->Put(adler32, 4);
    00038 }
    00039
    00040 unsigned int ZlibCompressor::GetCompressionLevel() const
    00041 {
    00042         static const unsigned int deflateToCompressionLevel[] = {0, 1, 1, 1, 2, 2, 2, 2, 2, 3};
    00043         return deflateToCompressionLevel[GetDeflateLevel()];
    00044 }
    00045
    00046 // *************************************************************
    00047
    00048 ZlibDecompressor::ZlibDecompressor(BufferedTransformation *attachment, bool repeat, int propagation)
    00049         : Inflator(attachment, repeat, propagation)
    00050 {
    00051 }
    00052
    00053 void ZlibDecompressor::ProcessPrestreamHeader()
    00054 {
    00055         m_adler32.Restart();
    00056
    00057         byte cmf;
    00058         byte flags;
    00059
    00060         if (!m_inQueue.Get(cmf) || !m_inQueue.Get(flags))
    00061                 throw HeaderErr();
    00062
    00063         if ((cmf*256+flags) % 31 != 0)
    00064                 throw HeaderErr();      // if you hit this exception, you're probably trying to decompress invalid data
    00065
    00066         if ((cmf & 0xf) != DEFLATE_METHOD)
    00067                 throw UnsupportedAlgorithm();
    00068
    00069         if (flags & FDICT_FLAG)
    00070                 throw UnsupportedPresetDictionary();
    00071
    00072         m_log2WindowSize = 8 + (cmf >> 4);
    00073 }
    00074
    00075 void ZlibDecompressor::ProcessDecompressedData(const byte *inString, size_t length)
    00076 {
    00077         AttachedTransformation()->Put(inString, length);
    00078         m_adler32.Update(inString, length);
    00079 }
    00080
    00081 void ZlibDecompressor::ProcessPoststreamTail()
    00082 {
    00083         FixedSizeSecBlock<byte, 4> adler32;
    00084         if (m_inQueue.Get(adler32, 4) != 4)
    00085                 throw Adler32Err();
    00086         if (!m_adler32.Verify(adler32))
    00087                 throw Adler32Err();
    00088 }
    00089
    00090 NAMESPACE_END