CWE-ou-minkata/Sources/Plasma/PubUtilLib/plResMgr/plDiffBuffer.h

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*==LICENSE==*/
//////////////////////////////////////////////////////////////////////////////
//
//  plDiffBuffer - A utility class for writing and applying a difference
//                 buffer--i.e. a buffer containing a series of modifications
//                 (specifically, adds and copys) that will modify an old
//                 data buffer to match a new one. It's a useful utility
//                 class when doing binary file patching, for example, as you
//                 can write out the changes to this class, get back a data
//                 buffer suitable for writing, then use this class again
//                 later to reconstruct the new buffer.
//
//                  This class is meant to construct diff buffers using two
//                  ops: add and copy. Basically, the syntax is defined so
//                  that to reconstruct the new buffer, you run through the 
//                  list of ops sequentially, each one defining the next
//                  chunk of data in the new buffer. Add ops will add new data
//                  to the buffer that didn't exist in the old buffer, and 
//                  copy ops will copy data that existed in the old buffer
//                  (from an arbitrary offset, to facilitate encoding data
//                  shuffling). Delete ops are implicit, as they simply aren't
//                  defined in the stream of ops.
//
//// History /////////////////////////////////////////////////////////////////
//
//  7.24.2002 mcn   - Created (Happy late b-day to me!)
//
//////////////////////////////////////////////////////////////////////////////

#ifndef _plDiffBuffer_h
#define _plDiffBuffer_h

#include "HeadSpin.h"
#include "hsStream.h"

//// Class Definition ////////////////////////////////////////////////////////

class hsRAMStream;
class plBSDiffBuffer;
class plDiffBuffer
{
    protected:

        hsBool      fWriting, f16BitMode;
        uint32_t      fNewLength;
        hsRAMStream *fStream;
        
        // Support for BSDiff patch buffers (Patching only)
        plBSDiffBuffer  *fBSDiffBuffer;
        hsBool          fIsBSDiff;

    public:

        plDiffBuffer( uint32_t newLength, uint32_t oldLength = 0 );     // Constructor for writing new buffers. oldLength isn't required but helpful for optimizations
        plDiffBuffer( void *buffer, uint32_t length );    // Constructor for applying a given diff set
                                                        // to an old buffer
        virtual ~plDiffBuffer();


        /// Creation/write functions

        // Add() appends an Add-New-Data operation to the diff buffer. The data supplied will be copied internally.
        void    Add( int32_t length, void *newData );

        // Copy() appends a Copy-Data-From-Old operation to the diff buffer
        void    Copy( int32_t length, uint32_t oldOffset );

        // GetBuffer() will copy the diff stream into a new buffer and return it. You are responsible for freeing the buffer.
        void    GetBuffer( uint32_t &length, void *&bufferPtr );


        /// Apply functions

        // Apply() will take this diff buffer and apply it to the given old buffer, allocating and producing a new buffer. You are responsible for freeing the new buffer.
        void    Apply( uint32_t oldLength, void *oldBuffer, uint32_t &newLength, void *&newBuffer );

};

#endif // _plDiffBuffer_h