111 lines
4.3 KiB
C#
111 lines
4.3 KiB
C#
// Licensed to the .NET Foundation under one or more agreements.
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// The .NET Foundation licenses this file to you under the MIT license.
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// See the LICENSE file in the project root for more information.
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#if NETCORE
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using System;
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using System.Diagnostics;
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using System.Threading;
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namespace SharpCompress.Buffers
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{
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internal sealed partial class DefaultArrayPool<T> : ArrayPool<T>
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{
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/// <summary>Provides a thread-safe bucket containing buffers that can be Rent'd and Return'd.</summary>
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private sealed class Bucket
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{
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internal readonly int _bufferLength;
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private readonly T[][] _buffers;
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private readonly int _poolId;
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private SpinLock _lock; // do not make this readonly; it's a mutable struct
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private int _index;
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/// <summary>
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/// Creates the pool with numberOfBuffers arrays where each buffer is of bufferLength length.
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/// </summary>
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internal Bucket(int bufferLength, int numberOfBuffers, int poolId)
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{
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_lock = new SpinLock(Debugger.IsAttached); // only enable thread tracking if debugger is attached; it adds non-trivial overheads to Enter/Exit
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_buffers = new T[numberOfBuffers][];
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_bufferLength = bufferLength;
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_poolId = poolId;
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}
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/// <summary>Gets an ID for the bucket to use with events.</summary>
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internal int Id => GetHashCode();
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/// <summary>Takes an array from the bucket. If the bucket is empty, returns null.</summary>
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internal T[] Rent()
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{
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T[][] buffers = _buffers;
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T[] buffer = null;
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// While holding the lock, grab whatever is at the next available index and
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// update the index. We do as little work as possible while holding the spin
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// lock to minimize contention with other threads. The try/finally is
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// necessary to properly handle thread aborts on platforms which have them.
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bool lockTaken = false, allocateBuffer = false;
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try
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{
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_lock.Enter(ref lockTaken);
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if (_index < buffers.Length)
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{
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buffer = buffers[_index];
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buffers[_index++] = null;
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allocateBuffer = buffer == null;
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}
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}
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finally
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{
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if (lockTaken) _lock.Exit(false);
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}
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// While we were holding the lock, we grabbed whatever was at the next available index, if
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// there was one. If we tried and if we got back null, that means we hadn't yet allocated
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// for that slot, in which case we should do so now.
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if (allocateBuffer)
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{
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buffer = new T[_bufferLength];
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}
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return buffer;
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}
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/// <summary>
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/// Attempts to return the buffer to the bucket. If successful, the buffer will be stored
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/// in the bucket and true will be returned; otherwise, the buffer won't be stored, and false
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/// will be returned.
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/// </summary>
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internal void Return(T[] array)
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{
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// Check to see if the buffer is the correct size for this bucket
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if (array.Length != _bufferLength)
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{
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throw new ArgumentException("Buffer not from pool", nameof(array));
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}
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// While holding the spin lock, if there's room available in the bucket,
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// put the buffer into the next available slot. Otherwise, we just drop it.
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// The try/finally is necessary to properly handle thread aborts on platforms
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// which have them.
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bool lockTaken = false;
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try
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{
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_lock.Enter(ref lockTaken);
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if (_index != 0)
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{
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_buffers[--_index] = array;
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}
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}
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finally
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{
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if (lockTaken) _lock.Exit(false);
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}
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}
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}
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}
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}
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#endif |