Decompress byte array to string via BinaryReader yields empty string

Question

I am trying to decompress a byte array and get it into a string using a binary reader. When the following code executes, the inStream position changes from 0 to the length of the array, but str is always an empty string.

BinaryReader br = null;
string str = String.Empty;

using (MemoryStream inStream = new MemoryStream(pByteArray))
{
    GZipStream zipStream = new GZipStream(inStream, CompressionMode.Decompress);
    BinaryReader br = new BinaryReader(zipStream);
    str = br.ReadString();
    inStream.Close();
    br.Close();
}

Solution

You haven't shown how is the data being compressed, but here's a full example of compressing and decompressing a buffer:

using System;
using System.IO;
using System.IO.Compression;
using System.Text;

class Program
{
    static void Main()
    {
        var test = "foo bar baz";

        var compressed = Compress(Encoding.UTF8.GetBytes(test));
        var decompressed = Decompress(compressed);
        Console.WriteLine(Encoding.UTF8.GetString(decompressed));
    }

    static byte[] Compress(byte[] data)
    {
        using (var compressedStream = new MemoryStream())
        using (var zipStream = new GZipStream(compressedStream, CompressionMode.Compress))
        {
            zipStream.Write(data, 0, data.Length);
            zipStream.Close();
            return compressedStream.ToArray();
        }
    }

    static byte[] Decompress(byte[] data)
    {
        using (var compressedStream = new MemoryStream(data))
        using (var zipStream = new GZipStream(compressedStream, CompressionMode.Decompress))
        using (var resultStream = new MemoryStream())
        {
            zipStream.CopyTo(resultStream);
            return resultStream.ToArray();
        }
    }
}

Comments

[Scar]

What does this error mean? "The magic number in GZip header is not correct. Make sure you are passing in a GZip stream."