DataFlex Requires Chilkat v11.0.0+

Decompress Large Binary File in Blocks

See more Compression Examples

Decompresses a large binary file in blocks. DataFlex

Use ChilkatAx-win32.pkg

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

    Move False To iSuccess

    //  This example requires the Chilkat API to have been previously unlocked.
    //  See Global Unlock Sample for sample code.

    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 previously compressed file for decompressing.
    //  See Compress Large File in Blocks

    Get ComOpenForRead Of hoFacSrc "c:/temp/qa_output/compressedBmp.dat" To iSuccess
    If (iSuccess = False) Begin
        Get ComLastErrorText Of hoFacSrc To sTemp1
        Showln sTemp1
        Procedure_Return
    End

    //  If we compress in 32K chunks, find out how many blocks there will be.
    Move 32768 To iBlockSize
    Get ComGetNumBlocks Of hoFacSrc iBlockSize To iNumBlocks

    //  Open an output file for the decompressed data.
    Get ComOpenForWrite Of hoFacDest "c:/temp/qa_output/decompressed.bmp" 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"

    //  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 hoCompressedBytes

        Get ComDecompressBytes Of hoCompress vCompressedBytes To hoDecompressedBytes
        Get ComFileWrite Of hoFacDest vDecompressedBytes 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 decompressing file."


End_Procedure