b313f47660
The default Stream implementation of this method has to rent an array so it can call the overload that accepts an array, and then copy the output over. This is because the array overload is required and the span overload was only added more recently. We can avoid the overhead of this by implementing the span overload and working with the destination span directly. Do so for all classes we have that derive from Stream, and redirect their array overload to the span overload for code reuse.
114 lines
3.5 KiB
C#
114 lines
3.5 KiB
C#
#region Copyright & License Information
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/*
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* Copyright (c) The OpenRA Developers and Contributors
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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(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(nameof(stream));
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if (!stream.CanRead)
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throw new ArgumentException("stream must be readable.", nameof(stream));
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baseStream = stream;
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}
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public sealed override bool CanSeek => false;
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public sealed override bool CanRead => true;
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public sealed override bool CanWrite => false;
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public override long Length => 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 override void Write(ReadOnlySpan<byte> buffer) { 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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return Read(buffer.AsSpan(offset, count));
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}
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public override int Read(Span<byte> buffer)
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{
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var copied = 0;
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ConsumeData(buffer, ref copied);
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while (copied < buffer.Length && !baseStreamEmpty)
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{
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baseStreamEmpty = BufferData(baseStream, data);
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ConsumeData(buffer, 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()"/>,
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/// <see cref="Read(byte[], int, int)"/> and <see cref="Read(Span{byte})"/> 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(Span<byte> buffer, ref int copied)
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{
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while (copied < buffer.Length && data.Count > 0)
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buffer[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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