Go

Streaming Compression

See more Compression Examples

Compress and decompress using a stream. Go

    success := false

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

    fac := chilkat.NewFileAccess()
    compress := chilkat.NewCompression()
    compress.SetAlgorithm("deflate")

    streamC := chilkat.NewStream()

    // 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..)
    streamC.SetSourceFile("qa_data/hamlet.xml")
    streamC.SetSinkFile("qa_output/hamlet_compressed.dat")

    // Compress from source to sink.
    success = compress.CompressStream(streamC)
    if success != true {
        fmt.Println(compress.LastErrorText())
        fac.DisposeFileAccess()
        compress.DisposeCompression()
        streamC.DisposeStream()
        return
    }

    fmt.Println("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.
    fmt.Println("Original size = ", fac.FileSize(streamC.SourceFile()))
    fmt.Println("Compressed size = ", fac.FileSize(streamC.SinkFile()))

    // Now do file-to-file decompression
    streamD := chilkat.NewStream()
    streamD.SetSourceFile("qa_output/hamlet_compressed.dat")
    streamD.SetSinkFile("qa_output/hamlet_restored.xml")

    // Decompress from source to sink.
    success = compress.DecompressStream(streamD)
    if success != true {
        fmt.Println(compress.LastErrorText())
        fac.DisposeFileAccess()
        compress.DisposeCompression()
        streamC.DisposeStream()
        streamD.DisposeStream()
        return
    }

    fmt.Println("File-to-file deflate decompression successful.")

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

    bFilesEqual := fac.FileContentsEqual(streamC.SourceFile(),streamD.SinkFile())
    if bFilesEqual != true {
        fmt.Println("The output file is not equal to the input file!")
    } else {
        fmt.Println("The file was successfully compressed and decompressed.")
    }

    // ---------------------------------------------------------------------
    // Now let's decompress again, but this time w/ the application reading
    // the decompressed data directly from a stream.
    streamA := chilkat.NewStream()

    streamA.SetSourceFile("qa_output/hamlet_compressed.dat")

    // Start decompressing in a background thread.
    c := make(chan *chilkat.Task)
    go compress.DecompressStreamAsync(streamA,c)
    task := <-c

    // Read decompressed data from streamA:
    var decompressedText *string = new(string)
    for (streamA.EndOfStream() != true) {
        if streamA.DataAvailable() == true {
            decompressedText = streamA.ReadString()
            fmt.Println(*decompressedText)
        }

    }

    // 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.
    for (task.Finished() != true) {
        task.SleepMs(20)
    }

    // The decompressor may have finished, but it is possible that data
    // remains to be flushed.  
    if streamA.DataAvailable() == true {
        decompressedText = streamA.ReadString()
        fmt.Println(*decompressedText)
    }

    // Did streamA succeed in reading the entire file?
    if task.TaskSuccess() != true {
        fmt.Println("async decompress failed:")
        fmt.Println(task.ResultErrorText())
        success = false
    }

    fmt.Println("The async decompress was successful.")

    fac.DisposeFileAccess()
    compress.DisposeCompression()
    streamC.DisposeStream()
    streamD.DisposeStream()
    streamA.DisposeStream()
    task.DisposeTask()