Working with BZIP2 Archives

Overview

BZIP2 is a Unix-friendly compression format known for good compression ratio and block-based processing. Aspose.ZIP for .NET provides the Bzip2Archive class to compress or extract a single data stream in .bz2 format.

Because BZIP2 stores one compressed stream rather than a collection of entries, it is best suited for compressing a single file. If you need to package multiple files, first create a TAR container and then compress it as tar.bz2.

Compress a File

Use SetSource to assign the source file or stream, then call Save.

    using (Bzip2Archive archive = new Bzip2Archive())
    {
        archive.SetSource("data.bin");
        archive.Save("data.bin.bz2");
    }

Choose Compression Block Size

Bzip2SaveOptions accepts block sizes from 1 to 9. Higher values usually improve compression ratio at the cost of more CPU time and memory.

    using (FileStream output = File.Open("data.bin.bz2", FileMode.Create))
    using (FileStream source = File.Open("data.bin", FileMode.Open, FileAccess.Read))
    using (Bzip2Archive archive = new Bzip2Archive())
    {
        archive.SetSource(source);
        archive.Save(output, new Bzip2SaveOptions(9));
    }

For large files, BZIP2 compression can also run in parallel. See parallel bzip2 compression for the CompressionThreads option.

Extract a BZIP2 Archive

You can open a .bz2 archive from a file path or stream and extract the decompressed data to any writable stream.

    using (Bzip2Archive archive = new Bzip2Archive("data.bin.bz2"))
    using (FileStream extracted = File.Create("data.bin"))
    {
        archive.Extract(extracted);
    }

If you prefer to work with the unpacked stream directly, call Open:

    using (Bzip2Archive archive = new Bzip2Archive("data.bin.bz2"))
    using (Stream unpacked = archive.Open())
    using (MemoryStream ms = new MemoryStream())
    {
        unpacked.CopyTo(ms);
    }

Report Extraction Progress

To monitor decompression progress, pass Bzip2LoadOptions and subscribe to ExtractionProgressed.

    Bzip2LoadOptions loadOptions = new Bzip2LoadOptions();
    loadOptions.ExtractionProgressed += (sender, args) =>
    {
        Console.WriteLine("{0} bytes extracted", args.ProceededBytes);
    };

    using (Bzip2Archive archive = new Bzip2Archive("data.bin.bz2", loadOptions))
    using (MemoryStream extracted = new MemoryStream())
    {
        archive.Extract(extracted);
    }

Cancel Extraction

If decompression may need to be interrupted, provide a CancellationToken in Bzip2LoadOptions.

    using (CancellationTokenSource cts = new CancellationTokenSource())
    {
        cts.CancelAfter(TimeSpan.FromSeconds(60));

        try
        {
            using (Bzip2Archive archive = new Bzip2Archive("big.bz2",
                new Bzip2LoadOptions() { CancellationToken = cts.Token }))
            using (MemoryStream extracted = new MemoryStream())
            {
                archive.Extract(extracted);
            }
        }
        catch (OperationCanceledException)
        {
            Console.WriteLine("Extraction was cancelled.");
        }
    }

Cancellation can leave partial data in the destination stream, so if you need all-or-nothing behavior, extract to a temporary target and discard it on cancellation.

Create a tar.bz2 Archive

To compress multiple files with BZIP2, first collect them into a TAR archive and then save that TAR stream through Bzip2Archive.

    using (FileStream output = File.Open("result.tar.bz2", FileMode.Create))
    using (TarArchive tar = new TarArchive())
    {
        tar.CreateEntry("alice29.txt", "alice29.txt");
        tar.CreateEntry("fields.c", "fields.c");

        using (Bzip2Archive archive = new Bzip2Archive())
        {
            archive.SetSource(tar, TarFormat.Pax);
            archive.Save(output, new Bzip2SaveOptions(9));
        }
    }