FromBase64Transform.cs

//
// System.Security.Cryptography.FromBase64Transform.cs
//
// Authors:
//	Sergey Chaban (serge@wildwestsoftware.com)
//	Sebastien Pouliot  <sebastien@ximian.com>
//
// Copyright (C) 2004-2005 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.Globalization;
#if SSHARP
using System;
using System.Runtime.InteropServices;
using GC = Crestron.SimplSharp.CrestronEnvironment.GC;
#else
using System.Runtime.InteropServices;
#endif

#if SSHARP
namespace SSMono.Security.Cryptography
#else
namespace System.Security.Cryptography
#endif
	{

	[Serializable]
	[ComVisible (true)]
	public enum FromBase64TransformMode : int
		{
		IgnoreWhiteSpaces,
		DoNotIgnoreWhiteSpaces
		}

	[ComVisible (true)]
	public class FromBase64Transform : ICryptoTransform
		{

		private FromBase64TransformMode mode;
		private byte[] accumulator;
		private int accPtr;
		private bool m_disposed;

		private const byte TerminatorByte = ((byte)'=');

		public FromBase64Transform ()
			: this (FromBase64TransformMode.IgnoreWhiteSpaces)
			{
			}

		public FromBase64Transform (FromBase64TransformMode whitespaces)
			{
			this.mode = whitespaces;
			accumulator = new byte[4];
			accPtr = 0;
			m_disposed = false;
			}

		~FromBase64Transform ()
			{
			Dispose (false);
			}

		public bool CanTransformMultipleBlocks
			{
			get { return false; }
			}

		public virtual bool CanReuseTransform
			{
			get { return true; }
			}

		public int InputBlockSize
			{
			get { return 1; }
			}

		public int OutputBlockSize
			{
			get { return 3; }
			}

		public void Clear ()
			{
			Dispose (true);
			}

#if NET_4_0
		public void Dispose ()
#else
		void IDisposable.Dispose ()
#endif
			{
			Dispose (true);
			GC.SuppressFinalize (this);  // Finalization is now unnecessary
			}

		protected virtual void Dispose (bool disposing)
			{
			if (!m_disposed)
				{
				// zeroize data
				if (accumulator != null)
					Array.Clear (accumulator, 0, accumulator.Length);

				// dispose unmanaged objects
				if (disposing)
					{
					// dispose managed objects
					accumulator = null;
					}
				m_disposed = true;
				}
			}

		private byte[] lookupTable;

		private byte lookup (byte input)
			{
			if (input >= lookupTable.Length)
				{
				throw new FormatException (
					Locale.GetText ("Invalid character in a Base-64 string."));
				}

			byte ret = lookupTable[input];
			if (ret == Byte.MaxValue)
				{
				throw new FormatException (
					Locale.GetText ("Invalid character in a Base-64 string."));
				}

			return ret;
			}

		private int ProcessBlock (byte[] output, int offset)
			{
			int rem = 0;
			if (accumulator[3] == TerminatorByte)
				rem++;
			if (accumulator[2] == TerminatorByte)
				rem++;

			lookupTable = Base64Constants.DecodeTable;
			int b0, b1, b2, b3;

			switch (rem)
				{
				case 0:
					b0 = lookup (accumulator[0]);
					b1 = lookup (accumulator[1]);
					b2 = lookup (accumulator[2]);
					b3 = lookup (accumulator[3]);
					output[offset++] = (byte)((b0 << 2) | (b1 >> 4));
					output[offset++] = (byte)((b1 << 4) | (b2 >> 2));
					output[offset] = (byte)((b2 << 6) | b3);
					break;
				case 1:
					b0 = lookup (accumulator[0]);
					b1 = lookup (accumulator[1]);
					b2 = lookup (accumulator[2]);
					output[offset++] = (byte)((b0 << 2) | (b1 >> 4));
					output[offset] = (byte)((b1 << 4) | (b2 >> 2));
					break;
				case 2:
					b0 = lookup (accumulator[0]);
					b1 = lookup (accumulator[1]);
					output[offset] = (byte)((b0 << 2) | (b1 >> 4));
					break;
				}

			return (3 - rem);
			}

		private void CheckInputParameters (byte[] inputBuffer, int inputOffset, int inputCount)
			{
			if (inputBuffer == null)
				throw new ArgumentNullException ("inputBuffer");
			if (inputOffset < 0)
				throw new ArgumentOutOfRangeException ("inputOffset", "< 0");
			if (inputCount > inputBuffer.Length)
				throw new OutOfMemoryException ("inputCount " + Locale.GetText ("Overflow"));
			if (inputOffset > inputBuffer.Length - inputCount)
				throw new ArgumentException ("inputOffset", Locale.GetText ("Overflow"));
			if (inputCount < 0)
				throw new OverflowException ("inputCount < 0");
			}

		public int TransformBlock (byte[] inputBuffer, int inputOffset, int inputCount, byte[] outputBuffer, int outputOffset)
			{
			if (m_disposed)
				throw new ObjectDisposedException ("FromBase64Transform");
			// LAMESPEC: undocumented exceptions
			CheckInputParameters (inputBuffer, inputOffset, inputCount);
			if ((outputBuffer == null) || (outputOffset < 0))
				throw new FormatException ("outputBuffer");

			int res = 0;

			while (inputCount > 0)
				{
				if (accPtr < 4)
					{
					byte b = inputBuffer[inputOffset++];
					if (mode == FromBase64TransformMode.IgnoreWhiteSpaces)
						{
						if (!Char.IsWhiteSpace ((char)b))
							accumulator[accPtr++] = b;
						}
					else
						{
						// don't ignore, we'll fail if bad data is provided
						accumulator[accPtr++] = b;
						}
					}
				if (accPtr == 4)
					{
					res += ProcessBlock (outputBuffer, outputOffset);
					outputOffset += 3;
					accPtr = 0;
					}
				inputCount--;
				}

			return res;
			}

		public byte[] TransformFinalBlock (byte[] inputBuffer, int inputOffset, int inputCount)
			{
			if (m_disposed)
				throw new ObjectDisposedException ("FromBase64Transform");
			// LAMESPEC: undocumented exceptions
			CheckInputParameters (inputBuffer, inputOffset, inputCount);

			int ws = 0;
			int terminator = 0;
			if (mode == FromBase64TransformMode.IgnoreWhiteSpaces)
				{
				// count whitespace inside string
				for (int i = inputOffset, j = 0; j < inputCount; i++, j++)
					{
					if (Char.IsWhiteSpace ((char)inputBuffer[i]))
						ws++;
					}
				// no more (useful) data
				if (ws == inputCount)
					return new byte[0];
				// there may be whitespace after the terminator
				int k = inputOffset + inputCount - 1;
				int n = System.Math.Min (2, inputCount);
				while (n > 0)
					{
					char c = (char)inputBuffer[k--];
					if (c == '=')
						{
						terminator++;
						n--;
						}
					else if (Char.IsWhiteSpace (c))
						{
						continue;
						}
					else
						{
						break;
						}
					}
				}
			else
				{
				if (inputBuffer[inputOffset + inputCount - 1] == TerminatorByte)
					terminator++;
				if (inputBuffer[inputOffset + inputCount - 2] == TerminatorByte)
					terminator++;
				}
			// some terminators could already be in the accumulator
			if ((inputCount < 4) && (terminator < 2))
				{
				if ((accPtr > 2) && (accumulator[3] == TerminatorByte))
					terminator++;
				if ((accPtr > 1) && (accumulator[2] == TerminatorByte))
					terminator++;
				}

			int count = ((accPtr + inputCount - ws) >> 2) * 3 - terminator;
			if (count <= 0)
				return new byte[0];

			// allocate the "right" ammount (to avoid multiple allocation/copy)
			byte[] result = new byte[count];
			TransformBlock (inputBuffer, inputOffset, inputCount, result, 0);
			return result;
			}
		}
	}