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/*
* Copyright (C) 2007-2012 Xagasoft, All rights reserved.
*
* This file is part of the libbu++ library and is released under the
* terms of the license contained in the file LICENSE.
*/
#ifndef BU_CIPHER_H
#define BU_CIPHER_H
#include "bu/filter.h"
#include "bu/util.h"
namespace Bu
{
/**
* Represents a nice base class for a stream filter block encryption scheme.
* This class handles efficient caching during reading and writing,
* encrypting and decrypting for block ciphers. For each individual cipher
* you only have to worry about the block encryption and decryption. Cipher
* modes are handled with seperate classes, see Bu::CipherModeCbc,
* Bu::CipherModeCfb, Bu::CipherModeEcb, and Bu::CipherModeOfb.
*
*
*/
template<int iBlockSize>
class Cipher : public Bu::Filter
{
public:
Cipher( Bu::Stream &rNext ) :
Bu::Filter( rNext ),
iReadBufFill( 0 ),
iReadBufPos( 0 ),
iWriteBufFill( 0 )
{
}
virtual ~Cipher()
{
}
virtual void start()
{
}
virtual Bu::size stop()
{
flush();
return 0;
}
virtual Bu::size read( void *pBuf, Bu::size iBytes )
{
Bu::size iRead = 0;
while( iRead < iBytes )
{
if( iReadBufFill < iBlockSize )
{
int iR = rNext.read(
aReadBuf+iReadBufFill,
iBlockSize-iReadBufFill
);
if( iR == 0 )
return iRead;
iReadBufFill += iR;
if( iReadBufFill == iBlockSize )
decipher( aReadBuf );
}
if( iReadBufFill == iBlockSize )
{
int iCpy = Bu::buMin( (int)(iBytes-iRead), iBlockSize-iReadBufPos );
memcpy( ((char *)pBuf)+iRead, aReadBuf+iReadBufPos, iCpy );
iRead += iCpy;
iReadBufPos += iCpy;
if( iReadBufPos == iBlockSize )
{
iReadBufPos = iReadBufFill = 0;
}
}
}
return iRead;
}
virtual Bu::size write( const void *pBuf, Bu::size iBytes )
{
Bu::size iPos = 0;
while( iPos < iBytes )
{
int iLeft = Bu::buMin((int)(iBytes-iPos),iBlockSize-iWriteBufFill);
memcpy( aWriteBuf+iWriteBufFill, (char *)pBuf+iPos, iLeft );
iPos += iLeft;
iWriteBufFill += iLeft;
if( iWriteBufFill == iBlockSize )
{
encipher( aWriteBuf );
rNext.write( aWriteBuf, iBlockSize );
iWriteBufFill = 0;
}
}
return iPos;
}
virtual void flush()
{
if( iWriteBufFill > 0 && iWriteBufFill < iBlockSize )
{
memset( aWriteBuf+iWriteBufFill, 0, iBlockSize-iWriteBufFill );
encipher( aWriteBuf );
rNext.write( aWriteBuf, iBlockSize );
iWriteBufFill = 0;
}
rNext.flush();
}
using Bu::Stream::read;
using Bu::Stream::write;
protected:
virtual void encipher( void *pData )=0;
virtual void decipher( void *pData )=0;
private:
char aReadBuf[iBlockSize];
char aWriteBuf[iBlockSize];
int iReadBufFill;
int iReadBufPos;
int iWriteBufFill;
};
};
#endif
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