65 lines
1.5 KiB
C#
65 lines
1.5 KiB
C#
namespace Phantom.Utils.Collections;
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public sealed class RingBuffer<T> {
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private readonly T[] buffer;
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private int writeIndex;
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public RingBuffer(int capacity) {
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if (capacity < 0) {
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throw new ArgumentException("Capacity must not be negative.", nameof(capacity));
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}
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this.buffer = new T[capacity];
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}
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public int Capacity => buffer.Length;
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public int Count { get; private set; }
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public T Last => Count == 0 ? throw new InvalidOperationException("Ring buffer is empty.") : buffer[IndexOfItemFromEnd(1)];
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private int IndexOfItemFromEnd(int offset) {
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return (writeIndex - offset + Capacity) % Capacity;
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}
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public void Add(T item) {
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if (Capacity == 0) {
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throw new InvalidOperationException("Ring buffer has no capacity.");
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}
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buffer[writeIndex++] = item;
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Count = Math.Max(writeIndex, Count);
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writeIndex %= Capacity;
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}
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public void Clear() {
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Count = 0;
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writeIndex = 0;
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}
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public IEnumerable<T> EnumerateLast(uint maximumItems) {
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if (Capacity == 0) {
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yield break;
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}
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int totalItemsToReturn = (int) Math.Min(maximumItems, Count);
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// Yield items until we hit the end of the buffer.
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int startIndex = IndexOfItemFromEnd(totalItemsToReturn);
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int endOrMaxIndex = Math.Min(startIndex + totalItemsToReturn, Count);
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for (int i = startIndex; i < endOrMaxIndex; i++) {
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yield return buffer[i];
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}
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// Wrap around and yield remaining items.
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int remainingItemsToReturn = totalItemsToReturn - (endOrMaxIndex - startIndex);
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for (int i = 0; i < remainingItemsToReturn; i++) {
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yield return buffer[i];
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}
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}
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}
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