Swift

Streaming Compression

See more Compression Examples

Compress and decompress using a stream. Swift

func chilkatTest() {
    var success: Bool = false

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

    let fac = CkoFileAccess()!
    let compress = CkoCompression()!
    compress.algorithm = "deflate"

    let streamC = CkoStream()!

    // 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.sourceFile = "qa_data/hamlet.xml"
    streamC.sinkFile = "qa_output/hamlet_compressed.dat"

    // Compress from source to sink.
    success = compress.compressStream(strm: streamC)
    if success != true {
        print("\(compress.lastErrorText!)")
        return
    }

    print("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.
    print("Original size = \(fac.fileSize(path: streamC.sourceFile).intValue)")
    print("Compressed size = \(fac.fileSize(path: streamC.sinkFile).intValue)")

    // Now do file-to-file decompression
    let streamD = CkoStream()!
    streamD.sourceFile = "qa_output/hamlet_compressed.dat"
    streamD.sinkFile = "qa_output/hamlet_restored.xml"

    // Decompress from source to sink.
    success = compress.decompressStream(strm: streamD)
    if success != true {
        print("\(compress.lastErrorText!)")
        return
    }

    print("File-to-file deflate decompression successful.")

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

    var bFilesEqual: Bool = fac.fileContentsEqual(path1: streamC.sourceFile, path2: streamD.sinkFile)
    if bFilesEqual != true {
        print("The output file is not equal to the input file!")
    }
    else {
        print("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.
    let streamA = CkoStream()!

    streamA.sourceFile = "qa_output/hamlet_compressed.dat"

    // Start decompressing in a background thread.
    var task: CkoTask? = compress.decompressStreamAsync(strm: streamA)
    success = task!.run()

    // Read decompressed data from streamA:
    var decompressedText: String?
    while (streamA.endOfStream != true) {
        if streamA.dataAvailable == true {
            decompressedText = streamA.readString()
            print("\(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.
    while (task!.finished != true) {
        task!.sleepMs(numMs: 20)
    }

    // The decompressor may have finished, but it is possible that data
    // remains to be flushed.  
    if streamA.dataAvailable == true {
        decompressedText = streamA.readString()
        print("\(decompressedText!)")
    }

    // Did streamA succeed in reading the entire file?
    if task!.taskSuccess != true {
        print("async decompress failed:")
        print("\(task!.resultErrorText!)")
        success = false
    }

    print("The async decompress was successful.")

}