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// --------------------------------------------------------------------------
//
// File
// Name: Compress.h
// Purpose: Interface to zlib compression
// Created: 5/12/03
//
// --------------------------------------------------------------------------
#ifndef COMPRESSCONTEXT__H
#define COMPRESSCONTEXT__H
#include <zlib.h>
#include "CompressException.h"
// --------------------------------------------------------------------------
//
// Class
// Name: Compress
// Purpose: Interface to zlib compression, only very slight wrapper.
// (Use CompressStream for a more friendly interface.)
// Created: 5/12/03
//
// --------------------------------------------------------------------------
template<bool Compressing>
class Compress
{
public:
Compress()
: mFinished(false),
mFlush(Z_NO_FLUSH)
{
// initialise stream
mStream.zalloc = Z_NULL;
mStream.zfree = Z_NULL;
mStream.opaque = Z_NULL;
mStream.data_type = Z_BINARY;
if((Compressing)?(deflateInit(&mStream, Z_DEFAULT_COMPRESSION))
:(inflateInit(&mStream)) != Z_OK)
{
THROW_EXCEPTION(CompressException, InitFailed)
}
mStream.avail_in = 0;
}
~Compress()
{
int r = 0;
if((r = ((Compressing)?(deflateEnd(&mStream))
:(inflateEnd(&mStream)))) != Z_OK)
{
BOX_WARNING("zlib error code = " << r);
if(r == Z_DATA_ERROR)
{
BOX_WARNING("End of compress/decompress "
"without all input being consumed, "
"possible corruption?");
}
else
{
THROW_EXCEPTION(CompressException, EndFailed)
}
}
}
// --------------------------------------------------------------------------
//
// Function
// Name: Compress<Function>::InputRequired()
// Purpose: Input required yet?
// Created: 5/12/03
//
// --------------------------------------------------------------------------
bool InputRequired()
{
return mStream.avail_in <= 0;
}
// --------------------------------------------------------------------------
//
// Function
// Name: Compress<Function>::Input(const void *, int)
// Purpose: Set the input buffer ready for next output call.
// Created: 5/12/03
//
// --------------------------------------------------------------------------
void Input(const void *pInBuffer, int InLength)
{
// Check usage
if(mStream.avail_in != 0)
{
THROW_EXCEPTION(CompressException, BadUsageInputNotRequired)
}
// Store info
mStream.next_in = (unsigned char *)pInBuffer;
mStream.avail_in = InLength;
}
// --------------------------------------------------------------------------
//
// Function
// Name: Compress<Function>::FinishInput()
// Purpose: When compressing, no more input will be given.
// Created: 5/12/03
//
// --------------------------------------------------------------------------
void FinishInput()
{
mFlush = Z_FINISH;
}
// --------------------------------------------------------------------------
//
// Function
// Name: Compress<Function>::Output(void *, int)
// Purpose: Get some output data
// Created: 5/12/03
//
// --------------------------------------------------------------------------
int Output(void *pOutBuffer, int OutLength, bool SyncFlush = false)
{
// need more input?
if(mStream.avail_in == 0 && mFlush != Z_FINISH && !SyncFlush)
{
return 0;
}
// Buffers
mStream.next_out = (unsigned char *)pOutBuffer;
mStream.avail_out = OutLength;
// Call one of the functions
int flush = mFlush;
if(SyncFlush && mFlush != Z_FINISH)
{
flush = Z_SYNC_FLUSH;
}
int ret = (Compressing)?(deflate(&mStream, flush)):(inflate(&mStream, flush));
if(SyncFlush && ret == Z_BUF_ERROR)
{
// No progress possible. Just return 0.
return 0;
}
// Check errors
if(ret < 0)
{
BOX_WARNING("zlib error code = " << ret);
THROW_EXCEPTION(CompressException, TransformFailed)
}
// Parse result
if(ret == Z_STREAM_END)
{
mFinished = true;
}
// Return how much data was output
return OutLength - mStream.avail_out;
}
// --------------------------------------------------------------------------
//
// Function
// Name: Compress<Function>::OutputHasFinished()
// Purpose: No more output to be recieved
// Created: 5/12/03
//
// --------------------------------------------------------------------------
bool OutputHasFinished()
{
return mFinished;
}
private:
z_stream mStream;
bool mFinished;
int mFlush;
};
template<typename Integer>
Integer Compress_MaxSizeForCompressedData(Integer InLen)
{
// Conservative rendition of the info found here: http://www.gzip.org/zlib/zlib_tech.html
int blocks = (InLen + 32*1024 - 1) / (32*1024);
return InLen + (blocks * 6) + 8;
}
#endif // COMPRESSCONTEXT__H
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