54c4a05062
The Stream.ReadByte method is implemented by allocating a 1 byte buffer and calling into Read(byte[], int, int). Override ReadByte in derived classes to avoid needing to allocate this small temp buffer. Also, fix some bugs in the stream implementations. Remove Write capability from MergedStream that didn't make sense. Add guards into SegmentStream to ensure reads and writes belonged to the segment - otherwise a reader or writer could access regions of the base stream that were outside the intended segment.
107 lines
3.3 KiB
C#
107 lines
3.3 KiB
C#
#region Copyright & License Information
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/*
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* Copyright 2007-2020 The OpenRA Developers (see AUTHORS)
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* This file is part of OpenRA, which is free software. It is made
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* available to you under the terms of the GNU General Public License
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* as published by the Free Software Foundation, either version 3 of
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* the License, or (at your option) any later version. For more
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* information, see COPYING.
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*/
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#endregion
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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 OpenRA.Primitives
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{
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/// <summary>
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/// Provides a read-only buffering layer so data can be streamed from sources where reading arbitrary amounts of
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/// data is difficult.
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/// </summary>
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public abstract class ReadOnlyAdapterStream : Stream
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{
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readonly Queue<byte> data = new Queue<byte>(1024);
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readonly Stream baseStream;
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bool baseStreamEmpty;
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protected ReadOnlyAdapterStream(Stream stream)
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{
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if (stream == null)
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throw new ArgumentNullException("stream");
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if (!stream.CanRead)
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throw new ArgumentException("stream must be readable.", "stream");
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baseStream = stream;
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}
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public sealed override bool CanSeek { get { return false; } }
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public sealed override bool CanRead { get { return true; } }
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public sealed override bool CanWrite { get { return false; } }
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public override long Length { get { throw new NotSupportedException(); } }
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public sealed override long Position
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{
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get { throw new NotSupportedException(); }
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set { throw new NotSupportedException(); }
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}
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public sealed override long Seek(long offset, SeekOrigin origin) { throw new NotSupportedException(); }
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public sealed override void SetLength(long value) { throw new NotSupportedException(); }
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public sealed override void WriteByte(byte value) { throw new NotSupportedException(); }
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public sealed override void Write(byte[] buffer, int offset, int count) { throw new NotSupportedException(); }
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public sealed override void Flush() { throw new NotSupportedException(); }
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public sealed override int ReadByte()
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{
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if (data.Count > 0)
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return data.Dequeue();
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while (!baseStreamEmpty)
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{
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baseStreamEmpty = BufferData(baseStream, data);
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if (data.Count > 0)
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return data.Dequeue();
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}
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return -1;
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}
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public sealed override int Read(byte[] buffer, int offset, int count)
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{
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var copied = 0;
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ConsumeData(buffer, offset, count, ref copied);
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while (copied < count && !baseStreamEmpty)
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{
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baseStreamEmpty = BufferData(baseStream, data);
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ConsumeData(buffer, offset, count, ref copied);
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}
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return copied;
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}
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/// <summary>
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/// Reads data into a buffer, which will be used to satisfy <see cref="ReadByte()"/> and
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/// <see cref="Read(byte[], int, int)"/> calls.
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/// </summary>
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/// <param name="baseStream">The source stream from which bytes should be read.</param>
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/// <param name="data">The queue where bytes should be enqueued. Do not dequeue from this buffer.</param>
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/// <returns>Return true if all data has been read; otherwise, false.</returns>
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protected abstract bool BufferData(Stream baseStream, Queue<byte> data);
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void ConsumeData(byte[] buffer, int offset, int count, ref int copied)
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{
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while (copied < count && data.Count > 0)
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buffer[offset + copied++] = data.Dequeue();
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}
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protected override void Dispose(bool disposing)
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{
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if (disposing)
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baseStream.Dispose();
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base.Dispose(disposing);
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}
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}
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}
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