(MFC) Streaming Compression

Compress and decompress using a stream.

Chilkat C/C++ Library Downloads MS Visual C/C++ Libs

See Also: Using MFC CString in Chilkat

#include <CkFileAccess.h>
#include <CkCompression.h>
#include <CkStream.h>
#include <CkTask.h>

void ChilkatSample(void)
    {
    CkString strOut;

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

    CkFileAccess fac;
    CkCompression compress;
    compress.put_Algorithm("deflate");

    CkStream streamC;

    // 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.put_SourceFile("qa_data/hamlet.xml");
    streamC.put_SinkFile("qa_output/hamlet_compressed.dat");

    // Compress from source to sink.
    bool success = compress.CompressStream(streamC);
    if (success != true) {
        strOut.append(compress.lastErrorText());
        strOut.append("\r\n");
        SetDlgItemText(IDC_EDIT1,strOut.getUnicode());
        return;
    }

    strOut.append("File-to-file deflate compression successful.");
    strOut.append("\r\n");
    // 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.
    strOut.append("Original size = ");
    strOut.appendInt(fac.FileSize(streamC.sourceFile()));
    strOut.append("\r\n");
    strOut.append("Compressed size = ");
    strOut.appendInt(fac.FileSize(streamC.sinkFile()));
    strOut.append("\r\n");

    // Now do file-to-file decompression
    CkStream streamD;
    streamD.put_SourceFile("qa_output/hamlet_compressed.dat");
    streamD.put_SinkFile("qa_output/hamlet_restored.xml");

    // Decompress from source to sink.
    success = compress.DecompressStream(streamD);
    if (success != true) {
        strOut.append(compress.lastErrorText());
        strOut.append("\r\n");
        SetDlgItemText(IDC_EDIT1,strOut.getUnicode());
        return;
    }

    strOut.append("File-to-file deflate decompression successful.");
    strOut.append("\r\n");

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

    bool bFilesEqual = fac.FileContentsEqual(streamC.sourceFile(),streamD.sinkFile());
    if (bFilesEqual != true) {
        strOut.append("The output file is not equal to the input file!");
        strOut.append("\r\n");
    }
    else {
        strOut.append("The file was successfully compressed and decompressed.");
        strOut.append("\r\n");
    }

    // ---------------------------------------------------------------------
    // Now let's decompress again, but this time w/ the application reading
    // the decompressed data directly from a stream.
    CkStream streamA;

    streamA.put_SourceFile("qa_output/hamlet_compressed.dat");

    // Start decompressing in a background thread.
    CkTask *task = compress.DecompressStreamAsync(streamA);
    success = task->Run();

    // Read decompressed data from streamA:
    const char *decompressedText = 0;
    while ((streamA.get_EndOfStream() != true)) {
        if (streamA.get_DataAvailable() == true) {
            decompressedText = streamA.readString();
            strOut.append(decompressedText);
            strOut.append("\r\n");
        }

    }

    // 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->get_Finished() != true)) {
        task->SleepMs(20);
    }

    // The decompressor may have finished, but it is possible that data
    // remains to be flushed.  
    if (streamA.get_DataAvailable() == true) {
        decompressedText = streamA.readString();
        strOut.append(decompressedText);
        strOut.append("\r\n");
    }

    // Did streamA succeed in reading the entire file?
    if (task->get_TaskSuccess() != true) {
        strOut.append("async decompress failed:");
        strOut.append("\r\n");
        strOut.append(task->resultErrorText());
        strOut.append("\r\n");
        success = false;
    }

    strOut.append("The async decompress was successful.");
    strOut.append("\r\n");


    SetDlgItemText(IDC_EDIT1,strOut.getUnicode());

    }