DataFlex Requires Chilkat v11.0.0+

Transition from Compression.BeginCompressBytes to FirstChunk/LastChunk

Provides instructions for replacing deprecated BeginCompressBytes method calls with using FirstChunk and LastChunk properties. DataFlex

Use ChilkatAx-win32.pkg

Procedure Test
    Boolean iSuccess
    Handle hoFacSrc
    Handle hoFacDest
    Integer iBlockSize
    Integer iNumBlocks
    Handle hoCompress
    Variant hoFileBytes
    Variant hoCompressedBytes
    Integer i
    String sTemp1

    Move False To iSuccess

    Get Create (RefClass(cComCkFileAccess)) To hoFacSrc
    If (Not(IsComObjectCreated(hoFacSrc))) Begin
        Send CreateComObject of hoFacSrc
    End
    Get Create (RefClass(cComCkFileAccess)) To hoFacDest
    If (Not(IsComObjectCreated(hoFacDest))) Begin
        Send CreateComObject of hoFacDest
    End

    //  Open a large binary file for reading.
    Get ComOpenForRead Of hoFacSrc "qa_data/bmp/big.bmp" To iSuccess
    If (iSuccess = False) Begin
        Get ComLastErrorText Of hoFacSrc To sTemp1
        Showln sTemp1
        Procedure_Return
    End

    //  If we compress in 64K chunks, find out how many blocks there will be.
    Move 65536 To iBlockSize
    Get ComGetNumBlocks Of hoFacSrc iBlockSize To iNumBlocks

    //  Open an output file for the compressed data.
    Get ComOpenForWrite Of hoFacDest "c:/temp/qa_output/compressedBmp.dat" To iSuccess
    If (iSuccess = False) Begin
        Get ComLastErrorText Of hoFacDest To sTemp1
        Showln sTemp1
        Procedure_Return
    End

    Get Create (RefClass(cComChilkatCompression)) To hoCompress
    If (Not(IsComObjectCreated(hoCompress))) Begin
        Send CreateComObject of hoCompress
    End
    Set ComAlgorithm Of hoCompress To "deflate"

    //  ----------------------------------------------------------------------------------
    //  This is the deprecated way of compressing in chunks using Begin/More/End methods..
    //  ----------------------------------------------------------------------------------
    Move 0 To i
    While (i < iNumBlocks)
        Get ComReadBlock Of hoFacSrc i iBlockSize To hoFileBytes
        If (i = 0) Begin
            Get ComBeginCompressBytes Of hoCompress vFileBytes To hoCompressedBytes
        End
        Else Begin
            Get ComMoreCompressBytes Of hoCompress vFileBytes To hoCompressedBytes
        End

        Get ComFileWrite Of hoFacDest vCompressedBytes To iSuccess

        Move (i + 1) To i
    Loop

    //  At the very end, flush any remaining compressed bytes, if any.
    Get ComEndCompressBytes Of hoCompress To hoCompressedBytes
    Get ComFileWrite Of hoFacDest vCompressedBytes To iSuccess

    Send ComFileClose To hoFacSrc
    Send ComFileClose To hoFacDest

    Showln "Finished compressing file."

    //  ----------------------------------------------------------------------------------
    //  This is new way of compressing in chunks using FirstChunk and LastChunk properties
    //  ----------------------------------------------------------------------------------

    Get ComOpenForRead Of hoFacSrc "qa_data/bmp/big.bmp" To iSuccess
    If (iSuccess = False) Begin
        Get ComLastErrorText Of hoFacSrc To sTemp1
        Showln sTemp1
        Procedure_Return
    End

    Get ComOpenForWrite Of hoFacDest "c:/temp/qa_output/compressedBmp2.dat" To iSuccess
    If (iSuccess = False) Begin
        Get ComLastErrorText Of hoFacDest To sTemp1
        Showln sTemp1
        Procedure_Return
    End

    //  Assuming numBlocks > 1
    Set ComFirstChunk Of hoCompress To True
    Set ComLastChunk Of hoCompress To False

    Move 0 To i
    While (i < iNumBlocks)
        Get ComReadBlock Of hoFacSrc i iBlockSize To hoFileBytes
        Get ComCompressBytes Of hoCompress vFileBytes To hoCompressedBytes

        Get ComFileWrite Of hoFacDest vCompressedBytes To iSuccess

        Move (i + 1) To i

        Set ComFirstChunk Of hoCompress To False
        If (i = (iNumBlocks - 1)) Begin
            Set ComLastChunk Of hoCompress To True
        End

    Loop

    Send ComFileClose To hoFacSrc
    Send ComFileClose To hoFacDest

    Showln "Finished compressing file 2."


End_Procedure