Create new FileStream out of a byte array

Question

I am attempting to create a new FileStream object from a byte array. I'm sure that made no sense at all so I will try to explain in further detail below.

Tasks I am completing: 1) Reading the source file which was previously compressed 2) Decompressing the data using GZipStream 3) copying the decompressed data into a byte array.

What I would like to change:

1) I would like to be able to use File.ReadAllBytes to read the decompressed data. 2) I would then like to create a new filestream object usingg this byte array.

In short, I want to do this entire operating using byte arrays. One of the parameters for GZipStream is a stream of some sort, so I figured I was stuck using a filestream. But, if some method exists where I can create a new instance of a FileStream from a byte array - then I should be fine.

Here is what I have so far:

FolderBrowserDialog fbd = new FolderBrowserDialog(); // Shows a browser dialog
 fbd.ShowDialog();

            // Path to directory of files to compress and decompress.
            string dirpath = fbd.SelectedPath;

            DirectoryInfo di = new DirectoryInfo(dirpath);


 foreach (FileInfo fi in di.GetFiles())
            {
                zip.Program.Decompress(fi);

            }

            // Get the stream of the source file.
            using (FileStream inFile = fi.OpenRead())
            {

                //Create the decompressed file.
                string outfile = @"C:\Decompressed.exe";
                {
                    using (GZipStream Decompress = new GZipStream(inFile,
                            CompressionMode.Decompress))
                    {
                        byte[] b = new byte[blen.Length];
                        Decompress.Read(b,0,b.Length);
                        File.WriteAllBytes(outfile, b);
                    }
                }
            }

Thanks for any help! Regards, Evan

Answer 1

Since you don't know how many bytes you'll be reading from the GZipStream, you can't really allocate an array for it. You need to read it all into a byte array and then use a MemoryStream to decompress.

const int BufferSize = 65536;
byte[] compressedBytes = File.ReadAllBytes("compressedFilename");
// create memory stream
using (var mstrm = new MemoryStream(compressedBytes))
{
    using(var inStream = new GzipStream(mstrm, CompressionMode.Decompress))
    {
        using (var outStream = File.Create("outputfilename"))
        {
            var buffer = new byte[BufferSize];
            int bytesRead;
            while ((bytesRead = inStream.Read(buffer, 0, BufferSize)) != 0)
            {
                outStream.Write(buffer, 0, bytesRead);
            }  
        }
    }
}

Answer 2

It sounds like you need to use a MemoryStream.

Answer 3

Here is what I ended up doing. I realize that I did not give sufficient information in my question - and I apologize for that - but I do know the size of the file I need to decompress as I am using it earlier in my program. This buffer is referred to as "blen".

string fi = @"C:\Path To Compressed File";
    // Get the stream of the source file.
           //     using (FileStream inFile = fi.OpenRead())
                using (MemoryStream infile1 = new MemoryStream(File.ReadAllBytes(fi)))
                {

                    //Create the decompressed file.
                    string outfile = @"C:\Decompressed.exe";
                    {
                        using (GZipStream Decompress = new GZipStream(infile1,
                                CompressionMode.Decompress))
                        {
                            byte[] b = new byte[blen.Length];
                            Decompress.Read(b,0,b.Length);
                            File.WriteAllBytes(outfile, b);
                        }
                    }
                }