Testing struct usage for QuadTree2.

src/DtronixCommon/Collections/Lists/DoubleList2.cs

@@ -0,0 +1,329 @@
+using System;
+using System.Collections.Concurrent;
+using System.Collections.Generic;
+using System.ComponentModel;
+using System.Diagnostics;
+using System.Linq;
+using System.Runtime.CompilerServices;
+using System.Runtime.InteropServices;
+using System.Text;
+using System.Threading.Tasks;
+using System.Xml.Linq;
+
+namespace DtronixCommon.Collections.Lists;
+
+/// <summary>
+/// List of double with varying size with a backing array.  Items erased are returned to be reused.
+/// </summary>
+/// <remarks>https://stackoverflow.com/a/48354356</remarks>
+internal class DoubleList2 : IDisposable
+{
+    [StructLayout(LayoutKind.Explicit)]
+    public struct ValType
+    {
+        [FieldOffset(0)] // 1 byte
+        internal double Value;
+        [FieldOffset(0)] // 4 bytes
+        internal int IntValue;
+
+        public static implicit operator ValType(double d) => new ValType() { Value = d };
+    }
+
+
+    public class Cache
+    {
+        private ConcurrentQueue<Item> _cachedLists = new ConcurrentQueue<Item>();
+        private readonly int _fieldCount;
+
+        public class Item
+        {
+            public readonly long ExpireTime;
+            public readonly DoubleList2 List;
+            private readonly ConcurrentQueue<Item> _returnQueue;
+
+            public Item(DoubleList2 list, ConcurrentQueue<Item> queue)
+            {
+                List = list;
+                _returnQueue = queue;
+            }
+
+            public void Return()
+            {
+                List.InternalCount = 0;
+                List._freeElement = -1;
+                _returnQueue.Enqueue(this);
+            }
+        }
+
+        public Cache(int fieldCount)
+        {
+            _fieldCount = fieldCount;
+        }
+
+        public Item Get()
+        {
+            if (!_cachedLists.TryDequeue(out var list))
+            {
+                return new Item(new DoubleList2(_fieldCount), _cachedLists);
+            }
+
+            return list;
+        }
+    }
+
+    /// <summary>
+    /// Contains the data.
+    /// </summary>
+    private ValType[]? _data;
+
+    /// <summary>
+    /// Number of fields which are used in the list.  This number is multuplied 
+    /// </summary>
+    private int _numFields = 0;
+
+    /// <summary>
+    /// Current number of elements the list contains.
+    /// </summary>
+    internal int InternalCount = 0;
+
+    /// <summary>
+    /// Index of the last free element in the array.  -1 if there are no free elements.
+    /// </summary>
+    private int _freeElement = -1;
+
+    /// <summary>
+    /// Number of elements the list contains.
+    /// </summary>
+    public int Count => InternalCount;
+
+    /// <summary>
+    /// Creates a new list of elements which each consist of integer fields.
+    /// 'fieldCount' specifies the number of integer fields each element has.
+    /// Capacity starts starts at 128.
+    /// </summary>
+    /// <param name="fieldCount">Number of fields </param>
+    public DoubleList2(int fieldCount)
+        : this(fieldCount, 128)
+    {
+    }
+
+    /// <summary>
+    /// Creates a new list of elements which each consist of integer fields with the specified number of elements.
+    /// 'fieldCount' specifies the number of integer fields each element has.
+    /// </summary>
+    /// <param name="fieldCount"></param>
+    /// <param name="capacity">Number of total elements this collection supports.  This ignores fieldCount.</param>
+    public DoubleList2(int fieldCount, int capacity)
+    {
+        _numFields = fieldCount;
+        _data = new ValType[capacity];
+    }
+
+    /// <summary>
+    /// Returns the value of the specified field for the nth element.
+    /// </summary>
+    /// <param name="index"></param>
+    /// <param name="field"></param>
+    /// <returns></returns>
+    [MethodImpl(MethodImplOptions.AggressiveInlining)]
+    public double Get(int index, int field)
+    {
+        Debug.Assert(index >= 0 && index < InternalCount && field >= 0 && field < _numFields);
+        return _data![index * _numFields + field].Value;
+    }
+
+    /// <summary>
+    /// Returns the range of values for the specified element.
+    /// WARNING: Does not perform bounds checks.
+    /// </summary>
+    /// <param name="index"></param>
+    /// <param name="fieldStart">Starting position of the field.</param>
+    /// <param name="fieldCount">
+    /// Nubmer of fields to return.  Make sure to not let this run outside
+    /// of the max and min ranges for fields.</param>
+    /// <returns>Span of data for the range</returns>
+    [MethodImpl(MethodImplOptions.AggressiveInlining)]
+    public ReadOnlySpan<ValType> Get(int index, int fieldStart, int fieldCount)
+    {
+        return new ReadOnlySpan<ValType>(_data, index * _numFields + fieldStart, fieldCount);
+
+       ref var type = ref Get2(index, fieldStart);
+
+    }
+
+    public ref ValType Get2(int index, int fieldStart)
+    {
+        return ref Unsafe.AddByteOffset(ref _data![0], new IntPtr((index * _numFields + fieldStart * 8)));
+    }
+
+    /// <summary>
+    /// Returns an integer from the currently passed field.
+    /// </summary>
+    /// <param name="index">index of the element to retrieve</param>
+    /// <param name="field">Field of the element to retrieve.</param>
+    /// <returns>Interger of the specified element field.</returns>
+    public int GetInt(int index, int field)
+    {
+        return (int)Get(index, field);
+    }
+
+    /// <summary>
+    /// Sets the value of the specified field for the nth element.
+    /// </summary>
+    /// <param name="index"></param>
+    /// <param name="field"></param>
+    /// <param name="value"></param>
+    public void Set(int index, int field, double value)
+    {
+        Debug.Assert(index >= 0 && index < InternalCount && field >= 0 && field < _numFields);
+        _data![index * _numFields + field].Value = value;
+    }
+
+    /// <summary>
+    /// Clears the list, making it empty.
+    /// </summary>
+    public void Clear()
+    {
+        InternalCount = 0;
+        _freeElement = -1;
+    }
+
+    /// <summary>
+    /// Inserts an element to the back of the list and returns an index to it.
+    /// </summary>
+    /// <returns></returns>
+    public int PushBack()
+    {
+        int newPos = (InternalCount + 1) * _numFields;
+
+        // If the list is full, we need to reallocate the buffer to make room
+        // for the new element.
+        if (newPos > _data!.Length)
+        {
+            // Use double the size for the new capacity.
+            int newCap = newPos * 2;
+
+            // Allocate new array and copy former contents.
+            var newArray = new ValType[newCap];
+            Array.Copy(_data, newArray, _data.Length);
+            _data = newArray;
+        }
+
+        return InternalCount++;
+    }
+
+    /// <summary>
+    /// Inserts an element to the back of the list and adds the passed values to the data.
+    /// </summary>
+    /// <returns></returns>
+    public int PushBack(ReadOnlySpan<ValType> values)
+    {
+        int newPos = (InternalCount + 1) * _numFields;
+
+        // If the list is full, we need to reallocate the buffer to make room
+        // for the new element.
+        if (newPos > _data!.Length)
+        {
+            // Use double the size for the new capacity.
+            int newCap = newPos * 2;
+
+            // Allocate new array and copy former contents.
+            var newArray = new ValType[newCap];
+            Array.Copy(_data, newArray, _data.Length);
+            _data = newArray;
+        }
+
+        values.CopyTo(_data.AsSpan(InternalCount * _numFields));
+
+        return InternalCount++;
+    }
+
+    /// <summary>
+    /// Removes the element at the back of the list.
+    /// </summary>
+    public void PopBack()
+    {
+        // Just decrement the list size.
+        Debug.Assert(InternalCount > 0);
+        --InternalCount;
+    }
+
+    public void Increment(int index, int field)
+    {
+        Debug.Assert(index >= 0 && index < InternalCount && field >= 0 && field < _numFields);
+        _data![index * _numFields + field].IntValue++;
+    }
+
+    public void Decrement(int index, int field)
+    {
+        Debug.Assert(index >= 0 && index < InternalCount && field >= 0 && field < _numFields);
+        _data![index * _numFields + field].IntValue--;
+    }
+
+    /// <summary>
+    /// Inserts an element to a vacant position in the list and returns an index to it.
+    /// </summary>
+    /// <returns></returns>
+    public int Insert()
+    {
+        // If there's a free index in the free list, pop that and use it.
+        if (_freeElement != -1)
+        {
+            int index = _freeElement;
+            int pos = index * _numFields;
+
+            // Set the free index to the next free index.
+            _freeElement = _data![pos].IntValue;
+
+            // Return the free index.
+            return index;
+        }
+
+        // Otherwise insert to the back of the array.
+        return PushBack();
+    }
+
+    /// <summary>
+    /// Inserts an element to a vacant position in the list and returns an index to it.
+    /// </summary>
+    /// <returns></returns>
+    public int Insert(ReadOnlySpan<ValType> values)
+    {
+        // If there's a free index in the free list, pop that and use it.
+        if (_freeElement != -1)
+        {
+            int index = _freeElement;
+            int pos = index * _numFields;
+
+            // Set the free index to the next free index.
+            _freeElement = _data![pos].IntValue;
+
+            // Return the free index.
+            values.CopyTo(_data.AsSpan(index * _numFields));
+            return index;
+        }
+
+        // Otherwise insert to the back of the array.
+        return PushBack(values);
+    }
+
+    /// <summary>
+    /// Removes the nth element in the list.
+    /// </summary>
+    /// <param name="index"></param>
+    public void Erase(int index)
+    {
+        // Push the element to the free list.
+        int pos = index * _numFields;
+        _data![pos].IntValue = _freeElement;
+        _freeElement = index;
+    }
+
+    /// <summary>
+    /// Disposes of the list.
+    /// </summary>
+    public void Dispose()
+    {
+        _data = null;
+    }
+}