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

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*==LICENSE==*/
//////////////////////////////////////////////////////////////////////////////
//
//  plBSDiffBuffer - A utility class for writing and applying a difference
//                  buffer--i.e. a buffer containing a series of modifications
//                  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 copied in structure (not substance) from
//                  plDiffBuffer. It is based on bsdiff-4.1 from BSD
//                  Linux (http://www.daemonology.org/bsdiff). It's *extremely*
//                  hard to read code (written by a PhD), but it works well. The
//                  original BSD code has been modified to have the bzip2 pipes 
//                  it used to compress data removed. It has also been converted
//                  to work a C++ utility class.
//
//                  There isn't really an Add or Copy command in bsdiff. It just
//                  uses three control numbers and two diff/data buffers.
//
//////////////////////////////////////////////////////////////////////////////

#ifndef _plBSDiffBuffer_h
#define _plBSDiffBuffer_h

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

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

class hsRAMStream;
class plBSDiffBuffer
{
    protected:

        hsBool          fWriting;
        uint32_t          fNewLength, fPatchLength;
        unsigned char*  fPatchBuffer;

    public:

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


        /// Creation/write functions

        //  Diff() creates the diff buffer from the new and old. 
        uint32_t  Diff( uint32_t oldLength, void *oldBuffer, uint32_t newLength, void *newBuffer );

        // 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() is another way to call Patch().
        uint32_t  Apply( uint32_t oldLength, void *oldBuffer, uint32_t &newLength, void *&newBuffer )
        { return Patch(oldLength, oldBuffer, newLength, newBuffer); };

        // Patch() 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.
        uint32_t  Patch( uint32_t oldLength, void *oldBuffer, uint32_t &newLength, void *&newBuffer );

    private:
        
        uint32_t  IReadUnsignedint8_t(unsigned char *buf);
        void    IWriteUnsignedint8_t(uint32_t x,unsigned char *buf);
        void    ISafeMemcpy(unsigned char *dest, unsigned char *src, size_t nBytes,
                            unsigned char *destend, unsigned char *srcend);
        void    ISplit(int32_t *I,int32_t *V,uint32_t start,uint32_t len,uint32_t h);
        void    IQSuffixSort(int32_t *I,int32_t *V,unsigned char *old,uint32_t oldsize);
        uint32_t  IMatchLen( unsigned char *oldBuffer, uint32_t oldLength,
                           unsigned char *newBuffer, uint32_t newLength);
        uint32_t  ISearch( int32_t *I,
                         unsigned char *oldBuffer, uint32_t oldLength,
                         unsigned char *newBuffer, uint32_t newLength,
                         uint32_t st, uint32_t en, int32_t *pos);


};

#endif // _plBSDiffBuffer_h