/*
 *   Mentalis.org Security Library
 * 
 *     Copyright © 2002-2005, The Mentalis.org Team
 *     All rights reserved.
 *     http://www.mentalis.org/
 *
 *
 *   Redistribution and use in source and binary forms, with or without
 *   modification, are permitted provided that the following conditions
 *   are met:
 *
 *     - Redistributions of source code must retain the above copyright
 *        notice, this list of conditions and the following disclaimer. 
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 *        may be used to endorse or promote products derived from this
 *        software without specific prior written permission. 
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*/

using System;
using System.Security.Cryptography;
using System.Runtime.InteropServices;
using Org.Mentalis.Security;

namespace Org.Mentalis.Security.Cryptography {
	/// <summary>
	/// Represents an ARCFour managed ICryptoTransform.
	/// </summary>
	internal class RC4UnmanagedTransform : ICryptoTransform {
		/// <summary>
		/// Initializes a new instance of the <see cref="RC4UnmanagedTransform"/> class.
		/// </summary>
		/// <param name="key">The key used to initialize the RC4 state.</param>
		public RC4UnmanagedTransform(byte[] key) {
			m_Key = new SymmetricKey(CryptoProvider.RsaFull, CryptoAlgorithm.RC4, key);
		}
		/// <summary>
		/// Gets a value indicating whether the current transform can be reused.
		/// </summary>
		/// <value>This property returns <b>true</b>.</value>
		public bool CanReuseTransform {
			get {
				return true;
			}
		}
		/// <summary>
		/// Gets a value indicating whether multiple blocks can be transformed.
		/// </summary>
		/// <value>This property returns <b>true</b>.</value>
		public bool CanTransformMultipleBlocks {
			get {
				return true;
			}
		}
		/// <summary>
		/// Gets the input block size.
		/// </summary>
		/// <value>This property returns 1.</value>
		public int InputBlockSize {
			get {
				return 1;
			}
		}
		/// <summary>
		/// Gets the output block size.
		/// </summary>
		/// <value>This property returns 1.</value>
		public int OutputBlockSize {
			get {
				return 1;
			}
		}
		/// <summary>
		/// Transforms the specified region of the input byte array and copies the resulting transform to the specified region of the output byte array.
		/// </summary>
		/// <param name="inputBuffer">The input for which to compute the transform.</param>
		/// <param name="inputOffset">The offset into the input byte array from which to begin using data.</param>
		/// <param name="inputCount">The number of bytes in the input byte array to use as data.</param>
		/// <param name="outputBuffer">The output to which to write the transform.</param>
		/// <param name="outputOffset">The offset into the output byte array from which to begin writing data.</param>
		/// <returns>The number of bytes written.</returns>
		/// <exception cref="ObjectDisposedException">The object has been disposed.</exception>
		/// <exception cref="ArgumentNullException"><paramref name="inputBuffer"/> or <paramref name="outputBuffer"/> is a null reference (<b>Nothing</b> in Visual Basic).</exception>
		/// <exception cref="ArgumentOutOfRangeException"><paramref name="inputOffset"/>, <paramref name="inputCount"/> or <paramref name="outputOffset"/> is invalid.</exception>
		public int TransformBlock(byte[] inputBuffer, int inputOffset, int inputCount, byte[] outputBuffer, int outputOffset) {
			if (m_Key == null)
				throw new ObjectDisposedException(this.GetType().FullName);
			if (inputBuffer == null || outputBuffer == null)
				throw new ArgumentNullException();
			if (inputCount < 0 || inputOffset < 0 || outputOffset < 0 ||inputOffset + inputCount > inputBuffer.Length || outputBuffer.Length - outputOffset < inputCount)
				throw new ArgumentOutOfRangeException();
			byte[] buffer = new byte[inputCount];
			int length = buffer.Length;
			Array.Copy(inputBuffer, inputOffset, buffer, 0, length);
			if (SspiProvider.CryptEncrypt(m_Key.Handle, 0, 0, 0, buffer, ref length, length) == 0)
				throw new CryptographicException("Could not transform data.");
			Array.Copy(buffer, 0, outputBuffer, outputOffset, length);
			Array.Clear(buffer, 0, buffer.Length);
			return length;
		}
		/// <summary>
		/// Transforms the specified region of the specified byte array.
		/// </summary>
		/// <param name="inputBuffer">The input for which to compute the transform.</param>
		/// <param name="inputOffset">The offset into the byte array from which to begin using data.</param>
		/// <param name="inputCount">The number of bytes in the byte array to use as data.</param>
		/// <returns>The computed transform.</returns>
		/// <exception cref="ObjectDisposedException">The object has been disposed.</exception>
		/// <exception cref="ArgumentNullException"><paramref name="inputBuffer"/> is a null reference (<b>Nothing</b> in Visual Basic).</exception>
		/// <exception cref="ArgumentOutOfRangeException"><paramref name="inputOffset"/> or <paramref name="inputCount"/> is invalid.</exception>
		public byte[] TransformFinalBlock(byte[] inputBuffer, int inputOffset, int inputCount ) {
			if (m_Key == null)
				throw new ObjectDisposedException(this.GetType().FullName);
			if (inputBuffer == null)
				throw new ArgumentNullException();
			if (inputCount < 0 || inputOffset < 0 ||inputOffset + inputCount > inputBuffer.Length)
				throw new ArgumentOutOfRangeException();
			byte[] buffer = new byte[inputCount];
			int length = buffer.Length;
			Array.Copy(inputBuffer, inputOffset, buffer, 0, length);
			if (SspiProvider.CryptEncrypt(m_Key.Handle, 0, 1, 0, buffer, ref length, length) == 0)
				throw new CryptographicException("Could not transform data.");
			return buffer;
		}
		/// <summary>
		/// Disposes of the cryptographic parameters.
		/// </summary>
		public void Dispose() {
			if (m_Key != null) {
				m_Key.Dispose();
				m_Key = null;
			}
			try {
				GC.SuppressFinalize(this);
			} catch {}
		}
		/// <summary>
		/// Finalizes the object.
		/// </summary>
		~RC4UnmanagedTransform() {
			Dispose();
		}
		/// <summary>
		/// Holds the <see cref="SymmetricKey"/> used for the cryptographic transformations.
		/// </summary>
		private SymmetricKey m_Key;
	}
}