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// **************************************************************************
// * This file is part of the FreeFileSync project. It is distributed under *
// * GNU General Public License: http://www.gnu.org/licenses/gpl-3.0 *
// * Copyright (C) Zenju (zenju AT gmx DOT de) - All Rights Reserved *
// **************************************************************************
#ifndef ZLIB_H_INCLUDED_428597064566
#define ZLIB_H_INCLUDED_428597064566
#include <zen/serialize.h>
namespace zen
{
class ZlibInternalError {};
// compression level must be between 0 and 9:
// 0: no compression
// 9: best compression
template <class BinContainer> //as specified in serialize.h
BinContainer compress(const BinContainer& stream, int level); //throw ZlibInternalError
//caveat: output stream is physically larger than input! => strip additional reserved space if needed: "BinContainer(output.begin(), output.end())"
template <class BinContainer>
BinContainer decompress(const BinContainer& stream); //throw ZlibInternalError
//######################## implementation ##########################
namespace impl
{
size_t zlib_compressBound(size_t len);
size_t zlib_compress (const void* src, size_t srcLen, void* trg, size_t trgLen, int level); //throw ZlibInternalError
size_t zlib_decompress(const void* src, size_t srcLen, void* trg, size_t trgLen); //throw ZlibInternalError
}
template <class BinContainer>
BinContainer compress(const BinContainer& stream, int level) //throw ZlibInternalError
{
BinContainer contOut;
if (!stream.empty()) //don't dereference iterator into empty container!
{
//save uncompressed stream size for decompression
const std::uint64_t uncompressedSize = stream.size(); //use portable number type!
contOut.resize(sizeof(uncompressedSize));
std::copy(reinterpret_cast<const char*>(&uncompressedSize),
reinterpret_cast<const char*>(&uncompressedSize) + sizeof(uncompressedSize),
&*contOut.begin());
const size_t bufferEstimate = impl::zlib_compressBound(stream.size()); //upper limit for buffer size, larger than input size!!!
contOut.resize(contOut.size() + bufferEstimate);
const size_t bytesWritten = impl::zlib_compress(&*stream.begin(),
stream.size(),
&*contOut.begin() + contOut.size() - bufferEstimate,
bufferEstimate,
level); //throw ZlibInternalError
if (bytesWritten < bufferEstimate)
contOut.resize(contOut.size() - (bufferEstimate - bytesWritten)); //caveat: unsigned arithmetics
//caveat: physical memory consumption still *unchanged*!
}
return contOut;
}
template <class BinContainer>
BinContainer decompress(const BinContainer& stream) //throw ZlibInternalError
{
BinContainer contOut;
if (!stream.empty()) //don't dereference iterator into empty container!
{
//retrieve size of uncompressed data
std::uint64_t uncompressedSize = 0; //use portable number type!
if (stream.size() < sizeof(uncompressedSize))
throw ZlibInternalError();
std::copy(&*stream.begin(),
&*stream.begin() + sizeof(uncompressedSize),
reinterpret_cast<char*>(&uncompressedSize));
//attention: contOut MUST NOT be empty! Else it will pass a nullptr to zlib_decompress() => Z_STREAM_ERROR although "uncompressedSize == 0"!!!
//secondary bug: don't dereference iterator into empty container!
if (uncompressedSize == 0) //cannot be 0: compress() directly maps empty -> empty container skipping zlib!
throw ZlibInternalError();
try
{
contOut.resize(static_cast<size_t>(uncompressedSize)); //throw std::bad_alloc
}
catch (std::bad_alloc&) //most likely due to data corruption!
{
throw ZlibInternalError();
}
const size_t bytesWritten = impl::zlib_decompress(&*stream.begin() + sizeof(uncompressedSize),
stream.size() - sizeof(uncompressedSize),
&*contOut.begin(),
static_cast<size_t>(uncompressedSize)); //throw ZlibInternalError
if (bytesWritten != static_cast<size_t>(uncompressedSize))
throw ZlibInternalError();
}
return contOut;
}
}
#endif //ZLIB_H_INCLUDED_428597064566
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