20240422

Core/mapbox-sdk-cs/Utils/CircularBuffer.cs

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+using System;
+using System.Collections;
+using System.Collections.Generic;
+using System.Text;
+
+namespace Mapbox.Utils
+{
+
+
+	public interface ICircularBuffer<T>
+	{
+		int Count { get; }
+		void Add(T item);
+		T this[int index] { get; }
+	}
+
+
+
+	/// <summary>
+	/// http://geekswithblogs.net/blackrob/archive/2014/09/01/circular-buffer-in-c.aspx
+	/// https://social.msdn.microsoft.com/Forums/vstudio/en-US/416a2175-b05d-43b1-b99a-a01c56550dbe/circular-buffer-in-net?forum=netfxbcl
+	/// https://en.wikipedia.org/wiki/Circular_buffer
+	/// </summary>
+	/// <typeparam name="T"></typeparam>
+	public class CircularBuffer<T> : ICircularBuffer<T>, IEnumerable<T>
+
+	{
+		private T[] _buffer;
+		private int _head;
+		private int _tail;
+
+
+		public CircularBuffer(int capacity)
+		{
+			if (capacity < 0) { throw new ArgumentOutOfRangeException("capacity", "must be positive"); }
+			_buffer = new T[capacity];
+			_head = 0;
+		}
+
+
+		public int Count { get; private set; }
+
+
+		public void Add(T item)
+		{
+			_head = (_head + 1) % _buffer.Length;
+			_buffer[_head] = item;
+			if (Count == _buffer.Length)
+			{
+				_tail = (_tail + 1) % _buffer.Length;
+			}
+			else
+			{
+				++Count;
+			}
+		}
+
+
+		/// <summary>
+		/// <para>ATTENTION!!! order is flipped like in rolling window</para>
+		/// <para>[0] is newest value</para>
+		/// </summary>
+		/// <param name="index"></param>
+		/// <returns></returns>
+		public T this[int index]
+		{
+			get
+			{
+				if (index < 0 || index >= _buffer.Length) { throw new ArgumentOutOfRangeException("index: " + index.ToString()); }
+
+				return _buffer[mod((_head - index), _buffer.Length)];
+			}
+		}
+
+
+		private int mod(int x, int m) // x mod m works for both positive and negative x (unlike x % m).
+		{
+			return (x % m + m) % m;
+		}
+
+		public IEnumerator<T> GetEnumerator()
+		{
+			if (Count == 0 || _buffer.Length == 0)
+			{
+				yield break;
+			}
+
+			for (var i = 0; i < Count; ++i) { yield return this[i]; }
+		}
+
+		IEnumerator IEnumerable.GetEnumerator()
+		{
+			return GetEnumerator();
+		}
+
+
+		public IEnumerable<T> GetEnumerable()
+		{
+			IEnumerator<T> enumerator = GetEnumerator();
+			while (enumerator.MoveNext())
+			{
+				yield return enumerator.Current;
+			}
+		}
+
+
+	}
+}