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Unity C# - Garbage-free List with Add/Remove functions
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| // Drop-in replacement for List<T>. Presized List so no garbage when adding/removing. | |
| // Further reading: | |
| // - Collections without the boxing - https://www.jacksondunstan.com/articles/5148 | |
| // - https://stackoverflow.com/questions/3737997/why-implement-ienumerablet-if-i-can-just-define-one-getenumerator | |
| using System; | |
| using System.Collections; | |
| using System.Collections.Generic; | |
| using UnityEngine; | |
| public class ListNonAlloc<T> : IEnumerable<T> | |
| { | |
| private T[] _array; | |
| private int _count; | |
| private int _expandSize; | |
| private ListNonAllocEnumerator _enumerator; | |
| private class ListNonAllocEnumerator : IEnumerator<T> | |
| { | |
| private ListNonAlloc<T> _list; | |
| private int _currentIndex = -1; | |
| public ListNonAllocEnumerator(ListNonAlloc<T> list) | |
| { | |
| _list = list; | |
| } | |
| public T Current => _list[_currentIndex]; | |
| object IEnumerator.Current => Current; | |
| public bool MoveNext() | |
| { | |
| _currentIndex++; | |
| return _currentIndex < _list.Count; | |
| } | |
| public void Reset() | |
| { | |
| _currentIndex = -1; | |
| } | |
| public void Dispose() | |
| { | |
| // Dispose resources if needed | |
| } | |
| } | |
| public IEnumerator<T> GetEnumerator() | |
| { | |
| _enumerator.Reset(); | |
| return _enumerator; | |
| } | |
| IEnumerator IEnumerable.GetEnumerator() => GetEnumerator(); | |
| /// <param name="expandSize">How much the array will expand when adding at max capacity.</param> | |
| public ListNonAlloc(int capacity, int expandSize = 20) | |
| { | |
| _array = new T[capacity]; | |
| _count = 0; | |
| _expandSize = expandSize; | |
| _enumerator = new ListNonAllocEnumerator(this); | |
| } | |
| public int Count => _count; | |
| public int Capacity => _array.Length; | |
| public void Add(T item) | |
| { | |
| if (_count < _array.Length) | |
| { | |
| _array[_count] = item; | |
| _count++; | |
| } | |
| else | |
| { | |
| // Auto-expand | |
| var newCapacity = _array.Length + _expandSize; | |
| var newArray = new T[newCapacity]; | |
| _array.AsSpan().CopyTo(newArray); | |
| _array = newArray; | |
| _array[_count] = item; | |
| _count++; | |
| } | |
| } | |
| public void Remove(T item) | |
| { | |
| int index = -1; | |
| for (int i = 0; i < _count; i++) | |
| { | |
| if (EqualityComparer<T>.Default.Equals(_array[i], item)) | |
| { | |
| index = i; | |
| break; | |
| } | |
| } | |
| if (index >= 0) | |
| { | |
| // Shift elements to fill the gap | |
| for (int i = index; i < _count - 1; i++) | |
| { | |
| _array[i] = _array[i + 1]; | |
| } | |
| _count--; | |
| } | |
| } | |
| public void RemoveAt(int index) | |
| { | |
| if (index >= 0 && index < _count) | |
| { | |
| // Shift elements to fill the gap | |
| for (int i = index; i < _count - 1; i++) | |
| { | |
| _array[i] = _array[i + 1]; | |
| } | |
| _count--; | |
| } | |
| else | |
| { | |
| // TODO: Optionally handle the case where the index is out of bounds | |
| Debug.LogError("Index out of bounds."); | |
| } | |
| } | |
| public bool Contains(T item) | |
| { | |
| for (int i = 0; i < _count; i++) | |
| { | |
| if (EqualityComparer<T>.Default.Equals(_array[i], item)) | |
| { | |
| return true; | |
| } | |
| } | |
| return false; | |
| } | |
| public T this[int index] | |
| { | |
| get | |
| { | |
| if (index >= 0 && index < _count) | |
| { | |
| return _array[index]; | |
| } | |
| else | |
| { | |
| // Optionally handle the case where the index is out of bounds | |
| Debug.LogError("Index out of bounds."); | |
| return default; | |
| } | |
| } | |
| set | |
| { | |
| if (index >= 0 && index < _count) | |
| { | |
| _array[index] = value; | |
| } | |
| else | |
| { | |
| // Optionally handle the case where the index is out of bounds | |
| Debug.LogError("Index out of bounds."); | |
| } | |
| } | |
| } | |
| public void Clear() | |
| { | |
| _count = 0; | |
| } | |
| } |
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