A class to test whether a file is a PE file and a managed assembly

Image.cs

//
// Image.cs
//
// Author:
// Jb Evain (jbevain@novell.com)
//
// WARNING: code now lives in http://github.com/jbevain/mono.reflection
//
// (C) 2009 Novell, Inc. (http://www.novell.com)
//
// Permission is hereby granted, free of charge, to any person obtaining
// a copy of this software and associated documentation files (the
// "Software"), to deal in the Software without restriction, including
// without limitation the rights to use, copy, modify, merge, publish,
// distribute, sublicense, and/or sell copies of the Software, and to
// permit persons to whom the Software is furnished to do so, subject to
// the following conditions:
//
// The above copyright notice and this permission notice shall be
// included in all copies or substantial portions of the Software.
//
// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
// EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
// MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
// NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE
// LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION
// OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION
// WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
//

using System;
using System.IO;

public class Image : IDisposable {

	Stream stream;

	Image (Stream stream)
	{
		stream.Position = 0;
		this.stream = stream;
	}

	bool Advance (int length)
	{
		if (stream.Position + length >= stream.Length)
			return false;

		stream.Seek (length, SeekOrigin.Current);
		return true;
	}

	bool MoveTo (uint position)
	{
		if (position >= stream.Length)
			return false;

		stream.Position = position;
		return true;
	}

	void IDisposable.Dispose ()
	{
		stream.Dispose ();
	}

	ushort ReadUInt16 ()
	{
		return (ushort) (stream.ReadByte ()
			| (stream.ReadByte () << 8));
	}

	uint ReadUInt32 ()
	{
		return (uint) (stream.ReadByte ()
			| (stream.ReadByte () << 8)
			| (stream.ReadByte () << 16)
			| (stream.ReadByte () << 24));
	}

	bool IsManagedAssembly ()
	{
		if (stream.Length < 318)
			return false;
		if (ReadUInt16 () != 0x5a4d)
			return false;
		if (!Advance (58))
			return false;
		if (!MoveTo (ReadUInt32 ()))
			return false;
		if (ReadUInt32 () != 0x00004550)
			return false;
		if (!Advance (20))
			return false;
		if (!Advance (ReadUInt16 () == 0x20b ? 222 : 206))
			return false;

		return ReadUInt32 () != 0;
	}

	public static bool IsAssembly (string file)
	{
		using (var stream = new FileStream (file, FileMode.Open, FileAccess.Read, FileShare.Read))
			return IsAssembly (stream);
	}

	static bool IsAssembly (Stream stream)
	{
		using (var image = new Image (stream))
			return image.IsManagedAssembly ();
	}
}