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74 lines
2.2 KiB
C#
74 lines
2.2 KiB
C#
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// Copyright (c) 2007-2017 ppy Pty Ltd <contact@ppy.sh>.
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// Licensed under the MIT Licence - https://raw.githubusercontent.com/ppy/osu/master/LICENCE
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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 osu.Game.Rulesets.Osu.OsuDifficulty.Utils
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{
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/// <summary>
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/// An indexed stack with Push() only, which disposes items at the bottom once the size limit has been reached.
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/// Indexing starts at the top of the stack.
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/// </summary>
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public class History<T> : IEnumerable<T>
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{
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public int Count { get; private set; } = 0;
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private T[] array;
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private int size;
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private int marker; // Marks the position of the most recently added item.
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public History(int size)
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{
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this.size = size;
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array = new T[size];
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marker = size; // Set marker to the end of the array, outside of the indexed range by one.
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}
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public T this[int i] // Index 0 returns the most recently added item.
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{
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get
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{
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if (i > Count - 1)
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throw new IndexOutOfRangeException();
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i += marker;
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if (i > size - 1)
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i -= size;
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return array[i];
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}
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}
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/// <summary>
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/// Adds the element as the most recent one in the history.
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/// The oldest element is disposed if the history is full.
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/// </summary>
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public void Push(T item) // Overwrite the oldest item instead of shifting every item by one with every addition.
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{
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if (marker == 0)
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marker = size - 1;
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else
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--marker;
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array[marker] = item;
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if (Count < size)
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++Count;
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}
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public IEnumerator<T> GetEnumerator()
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{
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for (int i = marker; i < size; ++i)
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yield return array[i];
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if (Count == size)
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for (int i = 0; i < marker; ++i)
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yield return array[i];
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}
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IEnumerator IEnumerable.GetEnumerator() => GetEnumerator();
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}
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}
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