Michael Handschuh
121 lines
4.1 KiB
C#
121 lines
4.1 KiB
C#
/*
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* QUANTCONNECT.COM - Democratizing Finance, Empowering Individuals.
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* Lean Algorithmic Trading Engine v2.0. Copyright 2014 QuantConnect Corporation.
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*
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* Licensed under the Apache License, Version 2.0 (the "License");
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* you may not use this file except in compliance with the License.
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* You may obtain a copy of the License at http://www.apache.org/licenses/LICENSE-2.0
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*
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* Unless required by applicable law or agreed to in writing, software
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* distributed under the License is distributed on an "AS IS" BASIS,
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* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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* See the License for the specific language governing permissions and
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* limitations under the License.
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*
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*/
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using System;
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using System.Collections;
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using System.Collections.Generic;
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namespace QuantConnect.Util
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{
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/// <summary>
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/// Defines an enumerable that can be enumerated many times while
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/// only performing a single enumeration of the root enumerable
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/// </summary>
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/// <typeparam name="T"></typeparam>
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public class MemoizingEnumerable<T> : IEnumerable<T>
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{
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private bool _finished;
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private readonly List<T> _buffer;
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private readonly IEnumerator<T> _enumerator;
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private readonly object _lock = new object();
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/// <summary>
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/// Initializes a new instance of the <see cref="MemoizingEnumerable{T}"/> class
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/// </summary>
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/// <param name="enumerable">The source enumerable to be memoized</param>
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public MemoizingEnumerable(IEnumerable<T> enumerable)
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: this(enumerable.GetEnumerator())
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{
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}
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/// <summary>
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/// Initializes a new instance of the <see cref="MemoizingEnumerable{T}"/> class
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/// </summary>
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/// <param name="enumerator">The source enumerator to be memoized</param>
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public MemoizingEnumerable(IEnumerator<T> enumerator)
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{
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_buffer = new List<T>();
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_enumerator = enumerator;
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}
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/// <summary>
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/// Returns an enumerator that iterates through the collection.
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/// </summary>
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/// <returns>
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/// A <see cref="T:System.Collections.Generic.IEnumerator`1"/> that can be used to iterate through the collection.
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/// </returns>
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/// <filterpriority>1</filterpriority>
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public IEnumerator<T> GetEnumerator()
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{
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int i = 0;
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while (true)
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{
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bool hasValue;
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// sync for multiple threads access to _enumerator and _buffer
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lock (_lock)
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{
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// check to see if we need to move next
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if (!_finished && i >= _buffer.Count)
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{
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hasValue = _enumerator.MoveNext();
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if (hasValue)
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{
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_buffer.Add(_enumerator.Current);
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}
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else
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{
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_finished = true;
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}
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}
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else
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{
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// we have a value if it's in the buffer
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hasValue = _buffer.Count > i;
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}
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}
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// yield the i'th element if we have it, otherwise stop enumeration
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if (hasValue)
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{
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yield return _buffer[i];
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}
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else
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{
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yield break;
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}
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// increment for next time
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i++;
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}
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}
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/// <summary>
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/// Returns an enumerator that iterates through a collection.
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/// </summary>
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/// <returns>
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/// An <see cref="T:System.Collections.IEnumerator"/> object that can be used to iterate through the collection.
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/// </returns>
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/// <filterpriority>2</filterpriority>
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IEnumerator IEnumerable.GetEnumerator()
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{
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return GetEnumerator();
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}
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}
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}
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