DataFlex

Streaming Compression

See more Compression Examples

Compress and decompress using a stream. DataFlex

Use ChilkatAx-win32.pkg

Procedure Test
    Boolean iSuccess
    Handle hoFac
    Handle hoCompress
    Variant vStreamC
    Handle hoStreamC
    Variant vStreamD
    Handle hoStreamD
    Boolean iBFilesEqual
    Variant vStreamA
    Handle hoStreamA
    Variant vTask
    Handle hoTask
    String sDecompressedText
    String sTemp1
    String sTemp2
    Integer iTemp1
    Boolean bTemp1

    Move False To iSuccess

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

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

    Get Create (RefClass(cComChilkatStream)) To hoStreamC
    If (Not(IsComObjectCreated(hoStreamC))) Begin
        Send CreateComObject of hoStreamC
    End

    // This example sets the source and sink of the stream to files.
    // A stream can have use other streams as a source or sink,
    // or the application can itself be the source/sink by directly
    // reading or writing a stream.  (See below for an example of this..)
    Set ComSourceFile Of hoStreamC To "qa_data/hamlet.xml"
    Set ComSinkFile Of hoStreamC To "qa_output/hamlet_compressed.dat"

    // Compress from source to sink.
    Get pvComObject of hoStreamC to vStreamC
    Get ComCompressStream Of hoCompress vStreamC To iSuccess
    If (iSuccess <> True) Begin
        Get ComLastErrorText Of hoCompress To sTemp1
        Showln sTemp1
        Procedure_Return
    End

    Showln "File-to-file deflate compression successful."
    // Note: The FileSize method returns a signed 32-bit integer.  If the file is potentially larger than 2GB, call FileSizeStr instead to return
    // the size of the file as a string, then convert to an integer value.
    Get ComFileSize Of hoFac (ComSourceFile(hoStreamC)) To iTemp1
    Showln "Original size = " iTemp1
    Get ComFileSize Of hoFac (ComSinkFile(hoStreamC)) To iTemp1
    Showln "Compressed size = " iTemp1

    // Now do file-to-file decompression
    Get Create (RefClass(cComChilkatStream)) To hoStreamD
    If (Not(IsComObjectCreated(hoStreamD))) Begin
        Send CreateComObject of hoStreamD
    End
    Set ComSourceFile Of hoStreamD To "qa_output/hamlet_compressed.dat"
    Set ComSinkFile Of hoStreamD To "qa_output/hamlet_restored.xml"

    // Decompress from source to sink.
    Get pvComObject of hoStreamD to vStreamD
    Get ComDecompressStream Of hoCompress vStreamD To iSuccess
    If (iSuccess <> True) Begin
        Get ComLastErrorText Of hoCompress To sTemp1
        Showln sTemp1
        Procedure_Return
    End

    Showln "File-to-file deflate decompression successful."

    // Let's double-check to see that the files are equal in size and content:

    Get ComSourceFile Of hoStreamC To sTemp1
    Get ComSinkFile Of hoStreamD To sTemp2
    Get ComFileContentsEqual Of hoFac sTemp1 sTemp2 To iBFilesEqual
    If (iBFilesEqual <> True) Begin
        Showln "The output file is not equal to the input file!"
    End
    Else Begin
        Showln "The file was successfully compressed and decompressed."
    End

    // ---------------------------------------------------------------------
    // Now let's decompress again, but this time w/ the application reading
    // the decompressed data directly from a stream.
    Get Create (RefClass(cComChilkatStream)) To hoStreamA
    If (Not(IsComObjectCreated(hoStreamA))) Begin
        Send CreateComObject of hoStreamA
    End

    Set ComSourceFile Of hoStreamA To "qa_output/hamlet_compressed.dat"

    // Start decompressing in a background thread.
    Get pvComObject of hoStreamA to vStreamA
    Get ComDecompressStreamAsync Of hoCompress vStreamA To vTask
    If (IsComObject(vTask)) Begin
        Get Create (RefClass(cComChilkatTask)) To hoTask
        Set pvComObject Of hoTask To vTask
    End
    Get ComRun Of hoTask To iSuccess

    // Read decompressed data from streamA:

    While ((ComEndOfStream(hoStreamA)) <> True)
        Get ComDataAvailable Of hoStreamA To bTemp1
        If (bTemp1 = True) Begin
            Get ComReadString Of hoStreamA To sDecompressedText
            Showln sDecompressedText
        End

    Loop

    // Let's make sure the background task finished and that the decompress was successful.
    // It should already be the case that the task is finished.
    While ((ComFinished(hoTask)) <> True)
        Send ComSleepMs To hoTask 20
    Loop

    // The decompressor may have finished, but it is possible that data
    // remains to be flushed.  
    Get ComDataAvailable Of hoStreamA To bTemp1
    If (bTemp1 = True) Begin
        Get ComReadString Of hoStreamA To sDecompressedText
        Showln sDecompressedText
    End

    // Did streamA succeed in reading the entire file?
    Get ComTaskSuccess Of hoTask To bTemp1
    If (bTemp1 <> True) Begin
        Showln "async decompress failed:"
        Get ComResultErrorText Of hoTask To sTemp1
        Showln sTemp1
        Move False To iSuccess
    End

    Showln "The async decompress was successful."


End_Procedure