// OffsetStream.cs
// ------------------------------------------------------------------
//
// Copyright (c)  2009 Dino Chiesa
// All rights reserved.
//
// This code module is part of DotNetZip, a zipfile class library.
//
// ------------------------------------------------------------------
//
// This code is licensed under the Microsoft Public License. 
// See the file License.txt for the license details.
// More info on: http://dotnetzip.codeplex.com
//
// ------------------------------------------------------------------
//
// last saved (in emacs): 
// Time-stamp: <2009-August-27 12:50:35>
//
// ------------------------------------------------------------------
//
// This module defines logic for handling reading of zip archives embedded 
// into larger streams.  The initial position of the stream serves as
// the base offset for all future Seek() operations.
// 
// ------------------------------------------------------------------

using System;
using System.IO;

namespace Ionic.Zip
{
	internal class OffsetStream : System.IO.Stream, System.IDisposable
	{
		private Int64 _originalPosition;
		private Stream _innerStream;

		public OffsetStream(Stream s)
				: base()
		{
			_originalPosition = s.Position;
			_innerStream = s;
		}

		public override int Read(byte[] buffer, int offset, int count)
		{
			return _innerStream.Read(buffer, offset, count);
		}

		public override void Write(byte[] buffer, int offset, int count)
		{
			throw new NotImplementedException();
		}

		public override bool CanRead
		{
			get { return _innerStream.CanRead; }
		}

		public override bool CanSeek
		{
			get { return _innerStream.CanSeek; }
		}

		public override bool CanWrite
		{
			get { return false; }
		}

		public override void Flush()
		{
			_innerStream.Flush();
		}

		public override long Length
		{
			get
			{
				return _innerStream.Length;
			}
		}

		public override long Position
		{
			get { return _innerStream.Position - _originalPosition; }
			set { _innerStream.Position = _originalPosition + value; }
		}


		public override long Seek(long offset, System.IO.SeekOrigin origin)
		{
			return _innerStream.Seek(_originalPosition + offset, origin) - _originalPosition;
		}


		public override void SetLength(long value)
		{
			throw new NotImplementedException();
		}

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

		public override void Close()
		{
			base.Close();
		}

	}
}