//
// System.IO.UnmanagedMemoryStream.cs
//
// Copyright (C) 2006 Sridhar Kulkarni, All Rights Reserved
//
// Authors:
// 	Sridhar Kulkarni (sridharkulkarni@gmail.com)
// 	Gert Driesen (drieseng@users.sourceforge.net)
//	Sebastien Pouliot  <sebastien@ximian.com>
//
// Copyright (C) 2005-2006, 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;
using System.Runtime.InteropServices;

namespace System.IO
{
	public class UnmanagedMemoryStream : Stream
	{
		long length;
		bool closed;
		long capacity;
		FileAccess fileaccess;
		IntPtr initial_pointer;
		long initial_position;
		long current_position;
#if NET_4_0
		SafeBuffer safebuffer;
#endif
		
		internal event EventHandler Closed;
		
#region Constructor
		protected UnmanagedMemoryStream()
		{
			closed = true;
		}

		[CLSCompliantAttribute(false)]
		public unsafe UnmanagedMemoryStream (byte *pointer, long length) :
			this (pointer, length, length, FileAccess.Read)
		{
		}
		
		[CLSCompliantAttribute(false)]
		public unsafe UnmanagedMemoryStream (byte *pointer, long length, long capacity, FileAccess access)
		{
			closed = true;
			Initialize (pointer, length, capacity, access);
		}

#if NET_4_0
		public UnmanagedMemoryStream (SafeBuffer buffer, long offset, long length) :
			this (buffer, offset, length, FileAccess.Read)
		{
		}

		public UnmanagedMemoryStream (SafeBuffer buffer, long offset, long length, FileAccess access)
		{
			closed = true;
			Initialize (buffer, offset, length, access);
		}
#endif
#endregion
	
#region Properties
		public override bool CanRead {
			get {
				return (!closed && (fileaccess != FileAccess.Write));
			}
		}

		public override bool CanSeek {
			get {
				return !closed;
			}
		}
		
		public override bool CanWrite {
			get {
				return (!closed && (fileaccess != FileAccess.Read));
			}
		}
		public long Capacity {
			get {
				if (closed)
					throw new ObjectDisposedException("The stream is closed");
				else
					return (capacity);
			}
		}
		public override long Length {
			get {
				if (closed)
					throw new ObjectDisposedException("The stream is closed");
				else
					return (length);
			}
		}

		public override long Position {
			get {
				if (closed)
					throw new ObjectDisposedException("The stream is closed");
				return (current_position);
			}
			set {
				if (closed)
					throw new ObjectDisposedException("The stream is closed");
				if (value < 0)
					throw new ArgumentOutOfRangeException("value", "Non-negative number required.");
				if (value > (long)Int32.MaxValue)
					throw new ArgumentOutOfRangeException("value", "The position is larger than Int32.MaxValue.");
				current_position = value;
			}
		}

		[CLSCompliantAttribute (false)]
		public unsafe byte* PositionPointer {
			get {
#if NET_4_0
				if (safebuffer != null)
					throw new NotSupportedException ("Not supported when using SafeBuffer");
#endif
				if (closed)
					throw new ObjectDisposedException("The stream is closed");
				if (current_position >= length)
					throw new IndexOutOfRangeException ("value");

				return (byte *) initial_pointer + current_position;
			}
			set {
#if NET_4_0
				if (safebuffer != null)
					throw new NotSupportedException ("Not supported when using SafeBuffer");
#endif
				if (closed)
					throw new ObjectDisposedException("The stream is closed");

				if (value < (byte *)initial_pointer)
					throw new IOException ("Address is below the inital address");

				Position = value - (byte*) initial_pointer;
			}
		}
#endregion
		
#region Methods
		public override int Read ([InAttribute] [OutAttribute] byte[] buffer, int offset, int count)
		{
			if (closed)
				throw new ObjectDisposedException("The stream is closed");
			
			if (buffer == null)
				throw new ArgumentNullException("buffer");
			if (offset < 0)
				throw new ArgumentOutOfRangeException("offset", "Non-negative number required.");
			if (count < 0)
				throw new ArgumentOutOfRangeException("count", "Non-negative number required.");
			if ((buffer.Length - offset) < count)
				throw new ArgumentException("The length of the buffer array minus the offset parameter is less than the count parameter");
			
			if (fileaccess == FileAccess.Write)
				throw new NotSupportedException("Stream does not support reading");

			if (current_position >= length)
				return 0;

			int progress = current_position + count < length ? count : (int) (length - current_position);
#if NET_4_0
			if (safebuffer != null) {
				unsafe {
					byte *ptr = null;
					try {
						safebuffer.AcquirePointer (ref ptr);
						Marshal.Copy (new IntPtr (ptr + current_position), buffer, offset, progress);
					} finally {
						if (ptr != null)
							safebuffer.ReleasePointer ();
					}
				}
			} else
#endif
			{
				Marshal.Copy (new IntPtr (initial_pointer.ToInt64 () + current_position), buffer, offset, progress);
			}
			current_position += progress;
			return progress;
		}

		public override int ReadByte ()
		{
			if (closed)
				throw new ObjectDisposedException("The stream is closed");
			
			if (fileaccess== FileAccess.Write)
				throw new NotSupportedException("Stream does not support reading");

			if (current_position >= length)
				return (-1);

#if NET_4_0
			if (safebuffer != null) {
				unsafe {
					byte *ptr = null;
					try {
						safebuffer.AcquirePointer (ref ptr);
						return (int) Marshal.ReadByte (new IntPtr (ptr), (int) current_position++);
					} finally {
						if (ptr != null)
							safebuffer.ReleasePointer ();
					}
				}
			} else
#endif
			{
				return (int) Marshal.ReadByte(initial_pointer, (int) current_position++);
			}
		}
		
		public override long Seek (long offset,	SeekOrigin loc)
		{
			if (closed)
				throw new ObjectDisposedException("The stream is closed");

			long refpoint;
			switch(loc) {
			case SeekOrigin.Begin:
				if (offset < 0)
					throw new IOException("An attempt was made to seek before the beginning of the stream");
				refpoint = initial_position;
				break;
			case SeekOrigin.Current:
				refpoint = current_position;
				break;
			case SeekOrigin.End:
				refpoint = length;
				break;
			default:
				throw new ArgumentException("Invalid SeekOrigin option");
			}
			refpoint += offset;
			if (refpoint < initial_position)
				throw new IOException("An attempt was made to seek before the beginning of the stream");
			current_position = refpoint;
			return(current_position);
		}
		 
		public override void SetLength (long value)
		{
#if NET_4_0
			if (safebuffer != null)
				throw new NotSupportedException ("Not supported when using SafeBuffer");
#endif
			if (closed)
				throw new ObjectDisposedException("The stream is closed");
			if (value < 0)
				throw new ArgumentOutOfRangeException("length", "Non-negative number required.");
			if (value > capacity)
				throw new IOException ("Unable to expand length of this stream beyond its capacity.");
			if (fileaccess == FileAccess.Read)
				throw new NotSupportedException ("Stream does not support writing.");
			length = value;
			if (length < current_position)
				current_position = length;
		}

		public override void Flush ()
		{
			if (closed)
				throw new ObjectDisposedException("The stream is closed");
			//This method performs no action for this class
			//but is included as part of the Stream base class
		}
		 
		protected override void Dispose (bool disposing)
		{
			if (closed)
				return;
			closed = true;
			if (Closed != null)
				Closed (this, null);
		}
		 
		public override void Write (byte[] buffer, int offset, int count)
		{
			if (closed)
				throw new ObjectDisposedException("The stream is closed");
			if (buffer == null)
				throw new ArgumentNullException("The buffer parameter is a null reference");
			if (offset < 0)
				throw new ArgumentOutOfRangeException("offset", "Non-negative number required.");
			if (count < 0)
				throw new ArgumentOutOfRangeException("count", "Non-negative number required.");
			if ((buffer.Length - offset) < count)
				throw new ArgumentException("The length of the buffer array minus the offset parameter is less than the count parameter");
			if (current_position > capacity - count)
				throw new NotSupportedException ("Unable to expand length of this stream beyond its capacity.");
			if (fileaccess == FileAccess.Read)
				throw new NotSupportedException ("Stream does not support writing.");

#if NET_4_0
			if (safebuffer != null) {
				unsafe {
					byte *dest = null;
					try {
						safebuffer.AcquirePointer (ref dest);
						fixed (byte *src = buffer) {
							dest += current_position;
							String.memcpy (dest, src + offset, count);
						}
					} finally {
						if (dest != null)
							safebuffer.ReleasePointer ();
					}
				}
			} else
#endif
			{
				unsafe {
					fixed (byte *src = buffer) {
						byte *dest = (byte *) initial_pointer + current_position;
						String.memcpy (dest, src + offset, count);
					}
				}
			}
			current_position += count;
			if (current_position > length)
				length = current_position;
		}
		
		public override void WriteByte (byte value)
		{
			if (closed)
				throw new ObjectDisposedException("The stream is closed");
			
			if (current_position == capacity)
				throw new NotSupportedException("The current position is at the end of the capacity of the stream");
			if (fileaccess == FileAccess.Read)
				throw new NotSupportedException("Stream does not support writing.");
 
#if NET_4_0
			if (safebuffer != null) {
				unsafe {
					byte *dest = null;
					try {
						safebuffer.AcquirePointer (ref dest);
						dest += current_position++;
						*dest = value;
					} finally {
						if (dest != null)
							safebuffer.ReleasePointer ();
					}
				}
			} else
#endif
			{
				unsafe {
					byte *dest = (byte *) initial_pointer + (int) current_position++;
					*dest = value;
				}
			}
			if (current_position > length)
				length = current_position;
		}

		[CLSCompliant (false)]
		protected unsafe void Initialize (byte* pointer, long length,
						  long capacity,
						  FileAccess access)
		{
			if (pointer == null)
				throw new ArgumentNullException("pointer");
			if (length < 0)
				throw new ArgumentOutOfRangeException("length", "Non-negative number required.");
			if (capacity < 0)
				throw new ArgumentOutOfRangeException("capacity", "Non-negative number required.");
			if (length > capacity)
				throw new ArgumentOutOfRangeException("length", "The length cannot be greater than the capacity.");
			if ((access < FileAccess.Read) || (access > FileAccess.ReadWrite))
				throw new ArgumentOutOfRangeException ("access", "Enum value was out of legal range.");
			if (!closed)
				throw new InvalidOperationException ("Called Initialize twice");
				
			fileaccess = access;
			this.length = length;
			this.capacity = capacity;
			initial_position = 0;
			current_position = initial_position;
			initial_pointer = new IntPtr ((void*)pointer);
			closed = false;
		}

#if NET_4_0
		protected void Initialize (SafeBuffer buffer, long offset, long length, FileAccess access)
		{
			if (buffer == null)
				throw new ArgumentNullException ("buffer");

			if (offset < 0)
				throw new ArgumentOutOfRangeException ("offset");

			if (length < 0)
				throw new ArgumentOutOfRangeException ("length");

			ulong blength = buffer.ByteLength;
			if ((blength - (ulong) length) < (ulong) offset)
				throw new ArgumentException ("Invalid offset and/or length");

			if (access < FileAccess.Read || access > FileAccess.ReadWrite)
				throw new ArgumentOutOfRangeException ("access");

			if (!closed)
				throw new InvalidOperationException ("Called Initialize twice");

			this.length = length;
			this.capacity = length;
			this.fileaccess = access;
			this.safebuffer = buffer;
			initial_position = offset;
			current_position = offset;
			closed = false;
		}
#endif
#endregion
	}
}