[C#] nubby math question

[Xerax]

I'm creating a dump from an external drive. I have the code for reading from the drive written, but I need to work out the best and fastest way to read from the drive. The code I have at the moment is:

public void beginBackup()
	    {
		    Reader r = _fatxDrive.Reader();
		    if (System.IO.File.Exists(_fileName))
			    System.IO.File.Delete(_fileName);
		    Writer w = new Writer(new System.IO.FileStream(_fileName, System.IO.FileMode.Create));
		    long ReadLength = 0x100000;
		    Dispatcher.Invoke(new Action(delegate { pbBackup.Maximum = r.BaseStream.Length; }));
		    while(r.BaseStream.Position != r.BaseStream.Length)
		    {
			    if (_cancelOp)
				    break;
			    if (r.BaseStream.Position + ReadLength > r.BaseStream.Length)
				    ReadLength = r.BaseStream.Length - r.BaseStream.Position;
			    w.Write(r.ReadBytes(Convert.ToInt32(ReadLength)));
		    }
		    w.Close();
		    Dispatcher.Invoke(new Action(delegate
		    {
			    FormFadeOut.Begin();
			    Backend.SettingsVault.Home.TaskbarItemInfo.ProgressState = System.Windows.Shell.TaskbarItemProgressState.None;
		    }));

But this tells me I'm exceeding the length of the drive.

[Andre S. Veteran]

The fastest most simple way is to create your input and output streams, and then call

input.CopyTo(output);

Only available in .NET 4.0+, though. I'm not sure why your code would exceed the length of the drive, only thing that's strange is ReadLength constant, where does that value come from? How do you specify that you want to read from the very start of the drive?

[Xerax]

ReadLength is a buffer I'm using. And I was forgetting to set the Basestream.Position to 0 before the read. Although the class I'm using did that for me. After tweaking my code a bit I managed to get it working. But, how would I set up CopyTo to be able to output progress? If I can't, or can't easily. I'll just stick to this method.

[Andre S. Veteran]

You can't. If you want to output progress you'll have to use custom code. Glad you could sort it out!