func Patch(old io.Reader, new io.Writer, patch io.Reader) error {
	var hdr header
	err := binary.Read(patch, signMagLittleEndian{}, &hdr)
	if err != nil {
		return err
	}
	if hdr.Magic != magic {
		return ErrCorrupt
	}
	if hdr.CtrlLen < 0 || hdr.DiffLen < 0 || hdr.NewSize < 0 {
		return ErrCorrupt
	}

	ctrlbuf := make([]byte, hdr.CtrlLen)
	_, err = io.ReadFull(patch, ctrlbuf)
	if err != nil {
		return err
	}
	cpfbz2 := bzip2.NewReader(bytes.NewReader(ctrlbuf))

	diffbuf := make([]byte, hdr.DiffLen)
	_, err = io.ReadFull(patch, diffbuf)
	if err != nil {
		return err
	}
	dpfbz2 := bzip2.NewReader(bytes.NewReader(diffbuf))

	// The entire rest of the file is the extra block.
	epfbz2 := bzip2.NewReader(patch)

	obuf, err := ioutil.ReadAll(old)
	if err != nil {
		return err
	}

	nbuf := make([]byte, hdr.NewSize)

	var oldpos, newpos int64
	for newpos < hdr.NewSize {
		var ctrl struct{ Add, Copy, Seek int64 }
		err = binary.Read(cpfbz2, signMagLittleEndian{}, &ctrl)
		if err != nil {
			return err
		}

		// Sanity-check
		if newpos+ctrl.Add > hdr.NewSize {
			return ErrCorrupt
		}

		// Read diff string
		_, err = io.ReadFull(dpfbz2, nbuf[newpos:newpos+ctrl.Add])
		if err != nil {
			return ErrCorrupt
		}

		// Add old data to diff string
		for i := int64(0); i < ctrl.Add; i++ {
			if oldpos+i >= 0 && oldpos+i < int64(len(obuf)) {
				nbuf[newpos+i] += obuf[oldpos+i]
			}
		}

		// Adjust pointers
		newpos += ctrl.Add
		oldpos += ctrl.Add

		// Sanity-check
		if newpos+ctrl.Copy > hdr.NewSize {
			return ErrCorrupt
		}

		// Read extra string
		_, err = io.ReadFull(epfbz2, nbuf[newpos:newpos+ctrl.Copy])
		if err != nil {
			return ErrCorrupt
		}

		// Adjust pointers
		newpos += ctrl.Copy
		oldpos += ctrl.Seek
	}

	// Write the new file
	for len(nbuf) > 0 {
		n, err := new.Write(nbuf)
		if err != nil {
			return err
		}
		nbuf = nbuf[n:]
	}

	return nil
}
func Patch(old io.Reader, new io.Writer, patch io.Reader) error {
	var hdr header
	err := binary.Read(patch, signMagLittleEndian{}, &hdr)
	if err != nil {
		return err
	}
	if hdr.Magic != magic {
		return ErrCorrupt
	}
	if hdr.CtrlLen < 0 || hdr.DiffLen < 0 || hdr.NewSize < 0 {
		return ErrCorrupt
	}

	ctrlbuf := make([]byte, hdr.CtrlLen)
	_, err = io.ReadFull(patch, ctrlbuf)
	if err != nil {
		return err
	}
	cpfbz2 := bzip2.NewReader(bytes.NewReader(ctrlbuf))

	diffbuf := make([]byte, hdr.DiffLen)
	_, err = io.ReadFull(patch, diffbuf)
	if err != nil {
		return err
	}
	dpfbz2 := bzip2.NewReader(bytes.NewReader(diffbuf))

	
	epfbz2 := bzip2.NewReader(patch)

	obuf, err := ioutil.ReadAll(old)
	if err != nil {
		return err
	}

	nbuf := make([]byte, hdr.NewSize)

	var oldpos, newpos int64
	for newpos < hdr.NewSize {
		var ctrl struct{ Add, Copy, Seek int64 }
		err = binary.Read(cpfbz2, signMagLittleEndian{}, &ctrl)
		if err != nil {
			return err
		}

		
		if newpos+ctrl.Add > hdr.NewSize {
			return ErrCorrupt
		}

		
		_, err = io.ReadFull(dpfbz2, nbuf[newpos:newpos+ctrl.Add])
		if err != nil {
			return ErrCorrupt
		}

		
		for i := int64(0); i < ctrl.Add; i++ {
			if oldpos+i >= 0 && oldpos+i < int64(len(obuf)) {
				nbuf[newpos+i] += obuf[oldpos+i]
			}
		}

		
		newpos += ctrl.Add
		oldpos += ctrl.Add

		
		if newpos+ctrl.Copy > hdr.NewSize {
			return ErrCorrupt
		}

		
		_, err = io.ReadFull(epfbz2, nbuf[newpos:newpos+ctrl.Copy])
		if err != nil {
			return ErrCorrupt
		}

		
		newpos += ctrl.Copy
		oldpos += ctrl.Seek
	}

	
	for len(nbuf) > 0 {
		n, err := new.Write(nbuf)
		if err != nil {
			return err
		}
		nbuf = nbuf[n:]
	}

	return nil
}
func Patch ( old io . Reader , new io . Writer , patch io . Reader ) error { var hdr header err := binary . Read ( patch , signMagLittleEndian { } , & hdr ) if err != nil { return err } if hdr . Magic != magic { return ErrCorrupt } if hdr . CtrlLen < 0 || hdr . DiffLen < 0 || hdr . NewSize < 0 { return ErrCorrupt } ctrlbuf := make ( [ ] byte , hdr . CtrlLen ) _ , err = io . ReadFull ( patch , ctrlbuf ) if err != nil { return err } cpfbz2 := bzip2 . NewReader ( bytes . NewReader ( ctrlbuf ) ) diffbuf := make ( [ ] byte , hdr . DiffLen ) _ , err = io . ReadFull ( patch , diffbuf ) if err != nil { return err } dpfbz2 := bzip2 . NewReader ( bytes . NewReader ( diffbuf ) ) // The entire rest of the file is the extra block. epfbz2 := bzip2 . NewReader ( patch ) obuf , err := ioutil . ReadAll ( old ) if err != nil { return err } nbuf := make ( [ ] byte , hdr . NewSize ) var oldpos , newpos int64 for newpos < hdr . NewSize { var ctrl struct { Add , Copy , Seek int64 } err = binary . Read ( cpfbz2 , signMagLittleEndian { } , & ctrl ) if err != nil { return err } // Sanity-check if newpos + ctrl . Add > hdr . NewSize { return ErrCorrupt } // Read diff string _ , err = io . ReadFull ( dpfbz2 , nbuf [ newpos : newpos + ctrl . Add ] ) if err != nil { return ErrCorrupt } // Add old data to diff string for i := int64 ( 0 ) ; i < ctrl . Add ; i ++ { if oldpos + i >= 0 && oldpos + i < int64 ( len ( obuf ) ) { nbuf [ newpos + i ] += obuf [ oldpos + i ] } } // Adjust pointers newpos += ctrl . Add oldpos += ctrl . Add // Sanity-check if newpos + ctrl . Copy > hdr . NewSize { return ErrCorrupt } // Read extra string _ , err = io . ReadFull ( epfbz2 , nbuf [ newpos : newpos + ctrl . Copy ] ) if err != nil { return ErrCorrupt } // Adjust pointers newpos += ctrl . Copy oldpos += ctrl . Seek } // Write the new file for len ( nbuf ) > 0 { n , err := new . Write ( nbuf ) if err != nil { return err } nbuf = nbuf [ n : ] } return nil }
// Patch applies patch to old, according to the bspatch algorithm,
// and writes the result to new.
Patch applies patch to old according to the bspatch algorithm and writes the result to new .