//  File name:          $Workfile: str_base.h $
//  Last modified:      $Modtime: 9/20/00 11:42a $
//  Last modified by:   $Author: Bill $
//  
//  VCS archive path:   $Archive: /Hank/DMM/FirmWare/Level3/ObDatMgr/str_base.h $
//  VCS revision:       $Revision: 6 $ 

//  External interfaces
class CPQDIF_StreamProcessor;

class CPQDIF_StreamIO
    {
    public:
	    CPQDIF_StreamIO();
        virtual ~CPQDIF_StreamIO();

    // Attributes
    public:

    // Operations
    public:
        virtual bool SeekPos( int pos ) = 0;
        virtual bool GetPos( int& pos ) = 0;
        virtual bool SeekEnd( void ) = 0;

        virtual BYTE * ReadBlock( long size, int& actualSize ) = 0;

		virtual bool CanWriteFull( void ) const { return m_canWriteFull; }
        virtual bool CanWriteIncremental( void ) const { return m_canWriteInc; }

        virtual bool BeginBlock( void );
        virtual bool AppendBlock( BYTE * buffer, long size );
        virtual bool WriteBlock( int &sizeActual ) = 0;

        virtual void Flush( void ) {}   //  Optional (default behavior: nothing)

        virtual bool ConnectProcessor( CPQDIF_StreamProcessor * proc );
        virtual long GetChecksum( void );
        virtual void ResetChecksum( void );

        //  Called by the processor
        //  =======================
        //  Dereferences data buffered in the stream for the processor to read.
        //  The number of bytes available is returned in sizeActual. If max is 0,
        //  the total remaining length of the input buffer is returned.
        //  Returns FALSE when at end of buffer, TRUE otherwise.
        virtual bool ProcessRead ( const BYTE * &buffer, long max, long& sizeActual );

        //  Reserves storage in the stream for the processor to write
        //  data into. 
        virtual bool ProcessWriteReserve( BYTE * &buffer, long size );

        //  This function is set the actual size of the buffer reserved
        //  by preceeding ProceWriteReserve call.
        virtual bool ProcessWriteRelease( long sizeActual );

    // Implementation
    protected:
        virtual bool ExecuteProcessorEncode( void );
        virtual bool ExecuteProcessorDecode( void );

    //  Member data
    protected:
        //  This is connected to the object, but not owned by it.
	    CPQDIF_StreamProcessor * m_processor;

        //  These are owned by the stream object
		bool		    m_canWriteFull;
		bool		    m_canWriteInc;

        CPQByteArray    m_buffRead;
        long            m_sizeRead;
        long            m_posRead;

        CPQByteArray    m_buffWrite;
        long            m_sizeWrite;
        long            m_posWrite;
    };