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Copy pathConcurrentPool.cs
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173 lines (149 loc) · 4.52 KB
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/*
* Copyright (c) 2018 Virgile Bello, Stanislav Denisov
*
* Permission is hereby granted, free of charge, to any person obtaining a copy
* of this software and associated documentation files (the "Software"), to deal
* in the Software without restriction, including without limitation the rights
* to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
* copies of the Software, and to permit persons to whom the Software is
* furnished to do so, subject to the following conditions:
*
* The above copyright notice and this permission notice shall be included in all
* copies or substantial portions of the Software.
*
* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
* IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
* FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
* AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
* LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
* OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
* SOFTWARE.
*/
using System;
using System.Threading;
namespace NetStack.Threading {
public sealed class ConcurrentPool<T> where T : class {
#if NET_4_6 || NET_STANDARD_2_0
private SpinLock _lock;
#else
private object _lock;
#endif
private readonly Func<T> _factory;
private Segment _head;
private Segment _tail;
public ConcurrentPool(int capacity, Func<T> factory) {
#if NET_4_6 || NET_STANDARD_2_0
_lock = new SpinLock();
#else
_lock = new Object();
#endif
_head = _tail = new Segment(capacity);
_factory = factory;
}
public T Acquire() {
while (true) {
var localHead = _head;
var count = localHead.Count;
if (count == 0) {
if (localHead.Next != null) {
#if NET_4_6 || NET_STANDARD_2_0
bool lockTaken = false;
try {
_lock.Enter(ref lockTaken);
if (_head.Next != null && _head.Count == 0)
_head = _head.Next;
}
finally {
if (lockTaken)
_lock.Exit(false);
}
#else
try {
Monitor.Enter(_lock);
if (_head.Next != null && _head.Count == 0)
_head = _head.Next;
}
finally {
Monitor.Exit(_lock);
}
#endif
} else {
return _factory();
}
} else if (Interlocked.CompareExchange(ref localHead.Count, count - 1, count) == count) {
var localLow = Interlocked.Increment(ref localHead.Low) - 1;
var index = localLow & localHead.Mask;
T item;
#if NET_4_6 || NET_STANDARD_2_0
var spinWait = new SpinWait();
#endif
while ((item = Interlocked.Exchange(ref localHead.Items[index], null)) == null) {
#if NET_4_6 || NET_STANDARD_2_0
spinWait.SpinOnce();
#else
Thread.SpinWait(1);
#endif
}
return item;
}
}
}
public void Release(T item) {
while (true) {
var localTail = _tail;
var count = localTail.Count;
if (count == localTail.Items.Length) {
#if NET_4_6 || NET_STANDARD_2_0
bool lockTaken = false;
try {
_lock.Enter(ref lockTaken);
if (_tail.Next == null && count == _tail.Items.Length)
_tail = _tail.Next = new Segment(_tail.Items.Length << 1);
}
finally {
if (lockTaken)
_lock.Exit(false);
}
#else
try {
Monitor.Enter(_lock);
if (_tail.Next == null && count == _tail.Items.Length)
_tail = _tail.Next = new Segment(_tail.Items.Length << 1);
}
finally {
Monitor.Exit(_lock);
}
#endif
} else if (Interlocked.CompareExchange(ref localTail.Count, count + 1, count) == count) {
var localHigh = Interlocked.Increment(ref localTail.High) - 1;
var index = localHigh & localTail.Mask;
#if NET_4_6 || NET_STANDARD_2_0
var spinWait = new SpinWait();
#endif
while (Interlocked.CompareExchange(ref localTail.Items[index], item, null) != null) {
#if NET_4_6 || NET_STANDARD_2_0
spinWait.SpinOnce();
#else
Thread.SpinWait(1);
#endif
}
return;
}
}
}
private class Segment {
public readonly T[] Items;
public readonly int Mask;
public int Low;
public int High;
public int Count;
public Segment Next;
public Segment(int size) {
if (size <= 0 || ((size & (size - 1)) != 0))
throw new ArgumentOutOfRangeException("Segment size must be power of two");
Items = new T[size];
Mask = size - 1;
}
}
}
}