Question

I am trying to compress and decompress a Stream using Compression.DeflateStream. Compressing seems to work correctly since the code below compresses my Stream to a 110 bytes long array. However, reading the decompressed Stream results in an empty string.

class Program
{
    static void Main(string[] args)
    {
        // Compress a random string value
        string value = Path.GetRandomFileName();
        byte[] compressedBytes;

        using (var writer = new StreamWriter(new MemoryStream()))
        {
            writer.Write(value);
            writer.Flush();
            writer.BaseStream.Position = 0;

            compressedBytes = Compress(writer.BaseStream);
        }

        // Decompress compressed bytes
        Stream decompressedStream = Decompress(compressedBytes);
        // here already applies: decompressedStream.Length == 0

        using (var reader = new StreamReader(decompressedStream))
        {
            string decompressedValue = reader.ReadToEnd();

            if (value == decompressedValue)
                Console.WriteLine("Success");
            else
                Console.WriteLine("Failed");
        }
    }

    private static byte[] Compress(Stream input)
    {
        using (var compressStream = new MemoryStream())
        using (var compressor = new DeflateStream(compressStream, CompressionMode.Compress))
        {
            input.CopyTo(compressor);
            return compressStream.ToArray();
        }
    }

    private static Stream Decompress(byte[] input)
    {
        var output = new MemoryStream();

        using (var compressStream = new MemoryStream(input))
        using (var decompressor = new DeflateStream(compressStream, CompressionMode.Decompress))
            decompressor.CopyTo(output);

        output.Position = 0;
        return output;
    }
}

Can anyone help me on this one?
Many thanks.

Answer 1

Fix your Compress function:

private static byte[] Compress(Stream input)
{
    using(var compressStream = new MemoryStream())
    using(var compressor = new DeflateStream(compressStream, CompressionMode.Compress))
    {
        input.CopyTo(compressor);
        compressor.Close();
        return compressStream.ToArray();
    }
}

compressed stream was not flushed before returning the resulting byte array.