144 lines
4.0 KiB
C#
144 lines
4.0 KiB
C#
//
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// Copyright (c) 2008-2011, Kenneth Bell
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//
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// Permission is hereby granted, free of charge, to any person obtaining a
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// copy of this software and associated documentation files (the "Software"),
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// to deal in the Software without restriction, including without limitation
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// the rights to use, copy, modify, merge, publish, distribute, sublicense,
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// and/or sell copies of the Software, and to permit persons to whom the
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// Software is furnished to do so, subject to the following conditions:
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//
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// The above copyright notice and this permission notice shall be included in
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// all copies or substantial portions of the Software.
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//
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// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
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// IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
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// FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
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// AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
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// LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
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// FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER
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// DEALINGS IN THE SOFTWARE.
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//
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using System;
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using System.Collections.Generic;
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using System.IO;
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namespace DiscUtils.Streams
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{
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/// <summary>
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/// A stream that returns Zero's.
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/// </summary>
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public class ZeroStream : MappedStream
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{
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private bool _atEof;
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private readonly long _length;
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private long _position;
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public ZeroStream(long length)
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{
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_length = length;
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}
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public override bool CanRead
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{
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get { return true; }
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}
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public override bool CanSeek
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{
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get { return true; }
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}
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public override bool CanWrite
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{
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get { return false; }
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}
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public override IEnumerable<StreamExtent> Extents
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{
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// The stream is entirely sparse
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get { return new List<StreamExtent>(0); }
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}
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public override long Length
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{
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get { return _length; }
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}
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public override long Position
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{
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get { return _position; }
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set
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{
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_position = value;
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_atEof = false;
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}
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}
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public override IEnumerable<StreamExtent> MapContent(long start, long length)
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{
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return new StreamExtent[0];
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}
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public override void Flush() {}
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public override int Read(byte[] buffer, int offset, int count)
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{
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if (_position > _length)
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{
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_atEof = true;
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throw new IOException("Attempt to read beyond end of stream");
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}
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if (_position == _length)
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{
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if (_atEof)
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{
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throw new IOException("Attempt to read beyond end of stream");
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}
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_atEof = true;
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return 0;
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}
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int numToClear = (int)Math.Min(count, _length - _position);
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Array.Clear(buffer, offset, numToClear);
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_position += numToClear;
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return numToClear;
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}
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public override long Seek(long offset, SeekOrigin origin)
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{
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long effectiveOffset = offset;
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if (origin == SeekOrigin.Current)
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{
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effectiveOffset += _position;
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}
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else if (origin == SeekOrigin.End)
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{
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effectiveOffset += _length;
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}
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_atEof = false;
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if (effectiveOffset < 0)
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{
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throw new IOException("Attempt to move before beginning of stream");
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}
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_position = effectiveOffset;
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return _position;
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}
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public override void SetLength(long value)
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{
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throw new NotSupportedException();
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}
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public override void Write(byte[] buffer, int offset, int count)
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{
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throw new NotSupportedException();
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}
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}
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} |