102 lines
3.4 KiB
C#
102 lines
3.4 KiB
C#
//
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// Copyright (c) 2017, Bianco Veigel
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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.IO;
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namespace DiscUtils.Streams
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{
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/// <summary>
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/// Stream wrapper to allow forward only seeking on not seekable streams
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/// </summary>
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public class PositionWrappingStream : WrappingStream
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{
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public PositionWrappingStream(SparseStream toWrap, long currentPosition, Ownership ownership)
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: base(toWrap, ownership)
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{
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_position = currentPosition;
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}
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private long _position;
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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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if (_position == value)
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return;
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Seek(value, SeekOrigin.Begin);
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}
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}
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public override long Seek(long offset, SeekOrigin origin)
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{
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if (base.CanSeek)
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{
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return base.Seek(offset, SeekOrigin.Current);
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}
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switch (origin)
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{
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case SeekOrigin.Begin:
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offset = offset - _position;
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break;
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case SeekOrigin.Current:
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offset = offset + _position;
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break;
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case SeekOrigin.End:
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offset = Length - offset;
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break;
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default:
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throw new ArgumentOutOfRangeException(nameof(origin), origin, null);
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}
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if (offset == 0)
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return _position;
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if (offset < 0)
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throw new NotSupportedException("backward seeking is not supported");
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var buffer = new byte[Sizes.OneKiB];
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while (offset > 0)
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{
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var read = base.Read(buffer, 0, (int)Math.Min(buffer.Length, offset));
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offset -= read;
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}
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return _position;
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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 int Read(byte[] buffer, int offset, int count)
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{
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var read = base.Read(buffer, offset, count);
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_position += read;
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return read;
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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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base.Write(buffer, offset, count);
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_position += count;
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}
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}
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} |