How to convert an Stream into a byte[] in C#?

Question

Is there a simple way or method to convert an Stream into a byte[] in C#?

Answer 1

Call next function like

byte[] m_Bytes = StreamHelper.ReadToEnd (mystream);

Function:

public static byte[] ReadToEnd(System.IO.Stream stream)
    {
        long originalPosition = stream.Position;
        stream.Position = 0;  

        try
        {
            byte[] readBuffer = new byte[4096];

            int totalBytesRead = 0;
            int bytesRead;

            while ((bytesRead = stream.Read(readBuffer, totalBytesRead, readBuffer.Length - totalBytesRead)) > 0)
            {
                totalBytesRead += bytesRead;

                if (totalBytesRead == readBuffer.Length)
                {
                    int nextByte = stream.ReadByte();
                    if (nextByte != -1)
                    {
                        byte[] temp = new byte[readBuffer.Length * 2];
                        Buffer.BlockCopy(readBuffer, 0, temp, 0, readBuffer.Length);
                        Buffer.SetByte(temp, totalBytesRead, (byte)nextByte);
                        readBuffer = temp;
                        totalBytesRead++;
                    }
                }
            }

            byte[] buffer = readBuffer;
            if (readBuffer.Length != totalBytesRead)
            {
                buffer = new byte[totalBytesRead];
                Buffer.BlockCopy(readBuffer, 0, buffer, 0, totalBytesRead);
            }
            return buffer;
        }
        finally
        {
            stream.Position = originalPosition; 
        }
    }

Answer 2

Stream s;
int len = (int)s.Length;
byte[] b = new byte[len];
int pos = 0;
while((r = s.Read(b, pos, len - pos)) > 0) {
    pos += r;
}

A slightly more complicated solution is necesary is s.Length exceeds Int32.MaxValue. But if you need to read a stream that large into memory, you might want to think about a different approach to your problem.

Edit: If your stream does not support the Length property, modify using Earwicker's workaround.

public static class StreamExtensions {
    // Credit to Earwicker
    public static void CopyStream(this Stream input, Stream output) {
        byte[] b = new byte[32768];
        int r;
        while ((r = input.Read(b, 0, b.Length)) > 0) {
            output.Write(b, 0, r);
        }
    }
}

[...]

Stream s;
MemoryStream ms = new MemoryStream();
s.CopyStream(ms);
byte[] b = ms.GetBuffer();

Answer 3

Quick and dirty technique:

    static byte[] StreamToByteArray(Stream inputStream)
    {
        if (!inputStream.CanRead)
        {
            throw new ArgumentException(); 
        }

        // This is optional
        if (inputStream.CanSeek)
        {
            inputStream.Seek(0, SeekOrigin.Begin);
        }

        byte[] output = new byte[inputStream.Length];
        int bytesRead = inputStream.Read(output, 0, output.Length);
        Debug.Assert(bytesRead == output.Length, "Bytes read from stream matches stream length");
        return output;
    }

Test:

    static void Main(string[] args)
    {
        byte[] data;
        string path = @"C:\Windows\System32\notepad.exe";
        using (FileStream fs = File.Open(path, FileMode.Open, FileAccess.Read))
        {
            data = StreamToByteArray(fs);
        }

        Debug.Assert(data.Length > 0);
        Debug.Assert(new FileInfo(path).Length == data.Length); 
    }

I would ask, why do you want to read a stream into a byte[], if you are wishing to copy the contents of a stream, may I suggest using MemoryStream and writing your input stream into a memory stream.

Answer 4

The handy helper function to have is:

public static void CopyStream(Stream input, Stream output)
{
    byte[] b = new byte[32768];
    int r;
    while ((r = input.Read(b, 0, b.Length)) > 0)
        output.Write(b, 0, r);
}

Then use that to copy to a MemoryStream and call GetBuffer on it:

Stream file = new FileStream("c:\\foo.txt", FileMode.Open);

MemoryStream mem = new MemoryStream();
CopyStream(file, mem);

// getting the internal buffer (no additional copying)
byte[] buffer = mem.GetBuffer();
long length = mem.Length; // the actual length of the data 
                          // (the array may be longer)

// if you need the array to be exactly as long as the data
byte[] truncated = mem.ToArray(); // makes another copy

Edit: originally I suggested using Jason's answer for a Stream that supports the Length property. But it had a flaw because it assumed that the Stream would return all its contents in a single Read, which is not necessarily true (not for a Socket, for example.) I don't know if there is an example of a Stream implementation in the BCL that does support Length but might return the data in shorter chunks than you request, but as anyone can inherit Stream this could easily be the case.

It's probably simpler for most cases to use the above general solution, but supposing you did want to read directly into an array that is bigEnough:

byte[] b = new byte[bigEnough];
int r, offset;
while ((r = input.Read(b, offset, b.Length - offset)) > 0)
    offset += r;

That is, repeatedly call Read and move the position you will be storing the data at.

Answer 5

You could try writing the data to a file first then using the File.ReadAllByes function.

public byte[] StreamToFileToArray(string fileName)
{
    // Setup whatever read size you want (small here for testing)
    byte[] buffer = new byte[32];
    string dump_file = "Dump.bin";
    using (Stream input = File.Open(fileName, FileMode.Open, FileAccess.Read))
    {
        using (BinaryWriter output = new BinaryWriter(new FileStream(dump_file, FileMode.Create)))
        {
            int bytesRead = input.Read(buffer, 0, buffer.Length);
            while (bytesRead > 0)
            {
                output.Write(buffer, 0, bytesRead);
                bytesRead = input.Read(buffer, 0, buffer.Length);
            }
        }
    }
    return File.ReadAllBytes(dump_file);
}

Answer 6

You could also try just reading in parts at a time and expanding the byte array being returned:

public byte[] StreamToByteArray(string fileName)
{
    byte[] total_stream = new byte[0];
    using (Stream input = File.Open(fileName, FileMode.Open, FileAccess.Read))
    {
        byte[] stream_array = new byte[0];
        // Setup whatever read size you want (small here for testing)
        byte[] buffer = new byte[32];// * 1024];
        int read = 0;

        while ((read = input.Read(buffer, 0, buffer.Length)) > 0)
        {
            stream_array = new byte[total_stream.Length + read];
            total_stream.CopyTo(stream_array, 0);
            Array.Copy(buffer, 0, stream_array, total_stream.Length, read);
            total_stream = stream_array;
        }
    }
    return total_stream;
}