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#if NET_4_0
//
// CyclicDeque.cs
//
// Author:
// Jérémie "Garuma" Laval <jeremie.laval@gmail.com>
//
// Copyright (c) 2009 Jérémie "Garuma" Laval
//
// 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.Collections.Generic;
using System.Threading;
namespace System.Threading.Tasks
{
internal enum PopResult {
Succeed,
Empty,
Abort
}
internal interface IDequeOperations<T>
{
void PushBottom (T obj);
PopResult PopBottom (out T obj);
PopResult PopTop (out T obj);
}
internal interface IValueReader
{
long Read (ref long value);
}
internal class CyclicDeque<T> : IDequeOperations<T>
{
readonly IValueReader reader;
const int BaseSize = 11;
class Reader32 : IValueReader
{
public long Read (ref long value)
{
return Interlocked.Read (ref value);
}
}
class Reader64 : IValueReader
{
public long Read (ref long value)
{
return value;
}
}
public CyclicDeque ()
{
// We do the distinction between 32bits and 64bits
if (IntPtr.Size == 4)
reader = new Reader32 ();
else
reader = new Reader64 ();
}
long bottom;
long top;
long upperBound;
CircularArray<T> array = new CircularArray<T> (BaseSize);
public void PushBottom (T obj)
{
long b = reader.Read (ref bottom);
var a = array;
// Take care of growing
if (b - upperBound >= a.Size - 1) {
upperBound = reader.Read (ref top);
a = a.Grow (b, upperBound);
Interlocked.Exchange (ref array, a);
}
// Register the new value
a[b] = obj;
Interlocked.Increment (ref bottom);
}
public PopResult PopBottom (out T obj)
{
obj = default (T);
long b = Interlocked.Decrement (ref bottom);
var a = array;
long t = reader.Read (ref top);
long size = b - t;
if (size < 0) {
// Set bottom to t
Interlocked.Add (ref bottom, t - b);
return PopResult.Empty;
}
obj = a[b];
if (size > 0)
return PopResult.Succeed;
Interlocked.Add (ref bottom, t + 1 - b);
if (Interlocked.CompareExchange (ref top, t + 1, t) != t)
return PopResult.Empty;
return PopResult.Succeed;
}
public PopResult PopTop (out T obj)
{
obj = default (T);
long t = reader.Read (ref top);
long b = reader.Read (ref bottom);
if (b - t <= 0)
return PopResult.Empty;
if (Interlocked.CompareExchange (ref top, t + 1, t) != t)
return PopResult.Abort;
var a = array;
obj = a[t];
return PopResult.Succeed;
}
public IEnumerable<T> GetEnumerable ()
{
var a = array;
return a.GetEnumerable ();
}
}
internal class CircularArray<T>
{
readonly int baseSize;
readonly int size;
readonly T[] segment;
public CircularArray (int baseSize)
{
this.baseSize = baseSize;
this.size = 1 << baseSize;
this.segment = new T[size];
}
public long Size {
get {
return size;
}
}
public T this[long index] {
get {
return segment[index % Size];
}
set {
segment[index % Size] = value;
}
}
public CircularArray<T> Grow (long bottom, long top)
{
var grow = new CircularArray<T> (baseSize + 1);
for (long i = top; i < bottom; i++) {
grow[i] = this[i];
}
return grow;
}
public IEnumerable<T> GetEnumerable ()
{
return ((IEnumerable<T>)segment);
}
}
}
#endif
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