Any way to use Stream.CopyTo to copy only certain number of bytes?

Question

Is there any way to use Stream.CopyTo to copy only certain number of bytes to destination stream? what is the best workaround?

Edit:
My workaround (some code omitted):

internal sealed class Substream : Stream 
    {
        private readonly Stream stream; 
        private readonly long origin;   
        private readonly long length; 
        private long position;        

        public Substream(Stream stream, long length)
        {
            this.stream = stream;
            this.origin = stream.Position;
            this.position = stream.Position;
            this.length = length;            
        }

public override int Read(byte[] buffer, int offset, int count)
        {
            var n = Math.Max(Math.Min(count, origin + length - position), 0);                
            int bytesRead = stream.Read(buffer, offset, (int) n);
            position += bytesRead;
            return bytesRead;            
        }
}

then to copy n bytes:

var substream = new Substream(stream, n);
                substream.CopyTo(stm);

Answer 1

The implementation of copying streams is not overly complicated. If you want to adapt it to copy only a certain number of bytes then it shouldn't be too difficult to tweak the existing method, something like this

public static void CopyStream(Stream input, Stream output, int bytes)
{
    byte[] buffer = new byte[32768];
    int read;
    while (bytes > 0 && 
           (read = input.Read(buffer, 0, Math.Min(buffer.Length, bytes))) > 0)
    {
        output.Write(buffer, 0, read);
        bytes -= read;
    }
}

The check for bytes > 0 probably isn't strictly necessary, but can't do any harm.