72 lines
2.4 KiB
C#
72 lines
2.4 KiB
C#
using System.Collections.Generic;
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namespace Cryville.Common.Buffers {
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/// <summary>
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/// A resource pool that allows reusing instances of lists of type <typeparamref name="T" />.
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/// </summary>
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/// <typeparam name="T">The item type of the lists in the pool.</typeparam>
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public class ListPool<T> {
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private class Bucket : ObjectPool<List<T>> {
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readonly int _size;
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public Bucket(int size, int capacity) : base(capacity) {
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_size = size;
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}
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protected override List<T> Construct() {
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return new List<T>(_size);
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}
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}
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Bucket[] _buckets;
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/// <summary>
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/// Creates an instance of the <see cref="ListPool{T}" /> class with the default maximum list size and bucket capacity.
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/// </summary>
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public ListPool() : this(0x40000000, 256) { }
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/// <summary>
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/// Creates an instance of the <see cref="ListPool{T}" /> class.
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/// </summary>
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/// <param name="maxSize">The maximum size of the lists in the pool.</param>
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/// <param name="capacityPerBucket">The capacity of each bucket. The pool groups lists of similar sizes into buckets for faster access.</param>
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public ListPool(int maxSize, int capacityPerBucket) {
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if (maxSize < 16) maxSize = 16;
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int num = GetID(maxSize) + 1;
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_buckets = new Bucket[num];
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for (int i = 0; i < num; i++) {
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_buckets[i] = new Bucket(GetSize(i), capacityPerBucket);
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}
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}
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/// <summary>
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/// Rents a list of the specified size from the pool. The size of the list must not be changed when it is rented.
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/// </summary>
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/// <param name="size">The size of the list.</param>
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/// <returns>A <see cref="List{T}" /> of the specified size.</returns>
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public List<T> Rent(int size) {
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int len2 = size;
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if (len2 < 16) len2 = 16;
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var list = _buckets[GetID(len2)].Rent();
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if (list.Count < size)
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for (int i = list.Count; i < size; i++) list.Add(default(T));
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else if (list.Count > size)
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list.RemoveRange(size, list.Count - size);
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return list;
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}
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/// <summary>
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/// Returns a rented list to the pool.
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/// </summary>
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/// <param name="list">The list to return.</param>
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public void Return(List<T> list) {
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int len2 = list.Capacity;
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if (len2 < 16) len2 = 16;
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_buckets[GetID(len2)].Return(list);
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}
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static int GetID(int size) {
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size -= 1;
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size >>= 4;
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int num = 0;
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for (; size != 0; size >>= 1) num++;
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return num;
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}
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static int GetSize(int id) {
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return 0x10 << id;
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}
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}
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}
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