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