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