maui-linux/Xamarin.Forms.Core/SplitOrderedList.cs

// SplitOrderedList.cs
//
// Copyright (c) 2010 Jérémie "Garuma" Laval
//
// Permission is hereby granted, free of charge, to any person obtaining a copy
// of this software and associated documentation files (the "Software"), to deal
// in the Software without restriction, including without limitation the rights
// to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
// copies of the Software, and to permit persons to whom the Software is
// furnished to do so, subject to the following conditions:
//
// The above copyright notice and this permission notice shall be included in
// all copies or substantial portions of the Software.
//
// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
// IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
// FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
// AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
// LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
// OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
// THE SOFTWARE.
//
//

using System;
using System.Collections.Generic;
using System.Threading;

namespace Xamarin.Forms
{
	internal class SplitOrderedList<TKey, T>
	{
		const int MaxLoad = 5;
		const uint BucketSize = 512;

		static readonly byte[] ReverseTable =
		{
			0, 128, 64, 192, 32, 160, 96, 224, 16, 144, 80, 208, 48, 176, 112, 240, 8, 136, 72, 200, 40, 168, 104, 232, 24, 152, 88, 216, 56, 184, 120, 248, 4,
			132, 68, 196, 36, 164, 100, 228, 20, 148, 84, 212, 52, 180, 116, 244, 12, 140, 76, 204, 44, 172, 108, 236, 28, 156, 92, 220, 60, 188, 124, 252, 2, 130, 66, 194, 34, 162, 98, 226, 18, 146, 82, 210,
			50, 178, 114, 242, 10, 138, 74, 202, 42, 170, 106, 234, 26, 154, 90, 218, 58, 186, 122, 250, 6, 134, 70, 198, 38, 166, 102, 230, 22, 150, 86, 214, 54, 182, 118, 246, 14, 142, 78, 206, 46, 174, 110,
			238, 30, 158, 94, 222, 62, 190, 126, 254, 1, 129, 65, 193, 33, 161, 97, 225, 17, 145, 81, 209, 49, 177, 113, 241, 9, 137, 73, 201, 41, 169, 105, 233, 25, 153, 89, 217, 57, 185, 121, 249, 5, 133, 69,
			197, 37, 165, 101, 229, 21, 149, 85, 213, 53, 181, 117, 245, 13, 141, 77, 205, 45, 173, 109, 237, 29, 157, 93, 221, 61, 189, 125, 253, 3, 131, 67, 195, 35, 163, 99, 227, 19, 147, 83, 211, 51, 179,
			115, 243, 11, 139, 75, 203, 43, 171, 107, 235, 27, 155, 91, 219, 59, 187, 123, 251, 7, 135, 71, 199, 39, 167, 103, 231, 23, 151, 87, 215, 55, 183, 119, 247, 15, 143, 79, 207, 47, 175, 111, 239, 31,
			159, 95, 223, 63, 191, 127, 255
		};

		static readonly byte[] LogTable =
		{
			0xFF, 0, 1, 1, 2, 2, 2, 2, 3, 3, 3, 3, 3, 3, 3, 3, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5,
			5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6,
			6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7,
			7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7,
			7, 7, 7, 7, 7, 7, 7
		};

		readonly IEqualityComparer<TKey> _comparer;

		readonly Node _head;
		readonly Node _tail;

		Node[] _buckets = new Node[BucketSize];
		int _count;
		int _size = 2;

		SimpleRwLock _slim = new SimpleRwLock();

		public SplitOrderedList(IEqualityComparer<TKey> comparer)
		{
			_comparer = comparer;
			_head = new Node().Init(0);
			_tail = new Node().Init(ulong.MaxValue);
			_head.Next = _tail;
			SetBucket(0, _head);
		}

		public int Count
		{
			get { return _count; }
		}

		public bool CompareExchange(uint key, TKey subKey, T data, Func<T, bool> check)
		{
			Node node;
			uint b = key % (uint)_size;
			Node bucket;

			if ((bucket = GetBucket(b)) == null)
				bucket = InitializeBucket(b);

			if (!ListFind(ComputeRegularKey(key), subKey, bucket, out node))
				return false;

			if (!check(node.Data))
				return false;

			node.Data = data;

			return true;
		}

		public bool Delete(uint key, TKey subKey, out T data)
		{
			uint b = key % (uint)_size;
			Node bucket;

			if ((bucket = GetBucket(b)) == null)
				bucket = InitializeBucket(b);

			if (!ListDelete(bucket, ComputeRegularKey(key), subKey, out data))
				return false;

			Interlocked.Decrement(ref _count);
			return true;
		}

		public bool Find(uint key, TKey subKey, out T data)
		{
			Node node;
			uint b = key % (uint)_size;
			data = default(T);
			Node bucket;

			if ((bucket = GetBucket(b)) == null)
				bucket = InitializeBucket(b);

			if (!ListFind(ComputeRegularKey(key), subKey, bucket, out node))
				return false;

			data = node.Data;

			return !node.Marked;
		}

		public IEnumerator<T> GetEnumerator()
		{
			Node node = _head.Next;

			while (node != _tail)
			{
				while (node.Marked || (node.Key & 1) == 0)
				{
					node = node.Next;
					if (node == _tail)
						yield break;
				}
				yield return node.Data;
				node = node.Next;
			}
		}

		public bool Insert(uint key, TKey subKey, T data)
		{
			Node current;
			return InsertInternal(key, subKey, data, null, out current);
		}

		public T InsertOrGet(uint key, TKey subKey, T data, Func<T> dataCreator)
		{
			Node current;
			InsertInternal(key, subKey, data, dataCreator, out current);
			return current.Data;
		}

		public T InsertOrUpdate(uint key, TKey subKey, Func<T> addGetter, Func<T, T> updateGetter)
		{
			Node current;
			bool result = InsertInternal(key, subKey, default(T), addGetter, out current);

			if (result)
				return current.Data;

			// FIXME: this should have a CAS-like behavior
			return current.Data = updateGetter(current.Data);
		}

		public T InsertOrUpdate(uint key, TKey subKey, T addValue, T updateValue)
		{
			Node current;
			if (InsertInternal(key, subKey, addValue, null, out current))
				return current.Data;

			// FIXME: this should have a CAS-like behavior
			return current.Data = updateValue;
		}

		// When we run out of space for bucket storage, we use a lock-based array resize
		void CheckSegment(uint segment, bool readLockTaken)
		{
			if (segment < _buckets.Length)
				return;

			if (readLockTaken)
				_slim.ExitReadLock();
			try
			{
				_slim.EnterWriteLock();
				while (segment >= _buckets.Length)
					Array.Resize(ref _buckets, _buckets.Length * 2);
			}
			finally
			{
				_slim.ExitWriteLock();
			}
			if (readLockTaken)
				_slim.EnterReadLock();
		}

		// Reverse integer bits
		static ulong ComputeDummyKey(uint key)
		{
			return (ulong)(((uint)ReverseTable[key & 0xff] << 24) | ((uint)ReverseTable[(key >> 8) & 0xff] << 16) | ((uint)ReverseTable[(key >> 16) & 0xff] << 8) | ReverseTable[(key >> 24) & 0xff]) << 1;
		}

		// Reverse integer bits and make sure LSB is set
		static ulong ComputeRegularKey(uint key)
		{
			return ComputeDummyKey(key) | 1;
		}

		// Bucket storage is abstracted in a simple two-layer tree to avoid too much memory resize
		Node GetBucket(uint index)
		{
			if (index >= _buckets.Length)
				return null;
			return _buckets[index];
		}

		// Turn v's MSB off
		static uint GetParent(uint v)
		{
			uint t, tt;

			// Find MSB position in v
			int pos = (tt = v >> 16) > 0 ? (t = tt >> 8) > 0 ? 24 + LogTable[t] : 16 + LogTable[tt] : (t = v >> 8) > 0 ? 8 + LogTable[t] : LogTable[v];

			return (uint)(v & ~(1 << pos));
		}

		Node InitializeBucket(uint b)
		{
			Node current;
			uint parent = GetParent(b);
			Node bucket;

			if ((bucket = GetBucket(parent)) == null)
				bucket = InitializeBucket(parent);

			Node dummy = new Node().Init(ComputeDummyKey(b));
			if (!ListInsert(dummy, bucket, out current, null))
				return current;

			return SetBucket(b, dummy);
		}

		bool InsertInternal(uint key, TKey subKey, T data, Func<T> dataCreator, out Node current)
		{
			Node node = new Node().Init(ComputeRegularKey(key), subKey, data);

			uint b = key % (uint)_size;
			Node bucket;

			if ((bucket = GetBucket(b)) == null)
				bucket = InitializeBucket(b);

			if (!ListInsert(node, bucket, out current, dataCreator))
				return false;

			int csize = _size;
			if (Interlocked.Increment(ref _count) / csize > MaxLoad && (csize & 0x40000000) == 0)
				Interlocked.CompareExchange(ref _size, 2 * csize, csize);

			current = node;

			return true;
		}

		bool ListDelete(Node startPoint, ulong key, TKey subKey, out T data)
		{
			Node rightNode = null, rightNodeNext = null, leftNode = null;
			data = default(T);
			Node markedNode = null;

			do
			{
				rightNode = ListSearch(key, subKey, ref leftNode, startPoint);
				if (rightNode == _tail || rightNode.Key != key || !_comparer.Equals(subKey, rightNode.SubKey))
					return false;

				data = rightNode.Data;
				rightNodeNext = rightNode.Next;

				if (!rightNodeNext.Marked)
				{
					if (markedNode == null)
						markedNode = new Node();
					markedNode.Init(rightNodeNext);

					if (Interlocked.CompareExchange(ref rightNode.Next, markedNode, rightNodeNext) == rightNodeNext)
						break;
				}
			} while (true);

			if (Interlocked.CompareExchange(ref leftNode.Next, rightNodeNext, rightNode) != rightNode)
				ListSearch(rightNode.Key, subKey, ref leftNode, startPoint);

			return true;
		}

		bool ListFind(ulong key, TKey subKey, Node startPoint, out Node data)
		{
			Node rightNode = null, leftNode = null;
			data = null;

			rightNode = ListSearch(key, subKey, ref leftNode, startPoint);
			data = rightNode;

			return rightNode != _tail && rightNode.Key == key && _comparer.Equals(subKey, rightNode.SubKey);
		}

		bool ListInsert(Node newNode, Node startPoint, out Node current, Func<T> dataCreator)
		{
			ulong key = newNode.Key;
			Node rightNode = null, leftNode = null;

			do
			{
				rightNode = current = ListSearch(key, newNode.SubKey, ref leftNode, startPoint);
				if (rightNode != _tail && rightNode.Key == key && _comparer.Equals(newNode.SubKey, rightNode.SubKey))
					return false;

				newNode.Next = rightNode;
				if (dataCreator != null)
					newNode.Data = dataCreator();
				if (Interlocked.CompareExchange(ref leftNode.Next, newNode, rightNode) == rightNode)
					return true;
			} while (true);
		}

		Node ListSearch(ulong key, TKey subKey, ref Node left, Node h)
		{
			Node leftNodeNext = null, rightNode = null;

			do
			{
				Node t = h;
				Node tNext = t.Next;
				do
				{
					if (!tNext.Marked)
					{
						left = t;
						leftNodeNext = tNext;
					}
					t = tNext.Marked ? tNext.Next : tNext;
					if (t == _tail)
						break;

					tNext = t.Next;
				} while (tNext.Marked || t.Key < key || (tNext.Key == key && !_comparer.Equals(subKey, t.SubKey)));

				rightNode = t;

				if (leftNodeNext == rightNode)
				{
					if (rightNode != _tail && rightNode.Next.Marked)
						continue;
					return rightNode;
				}

				if (Interlocked.CompareExchange(ref left.Next, rightNode, leftNodeNext) == leftNodeNext)
				{
					if (rightNode != _tail && rightNode.Next.Marked)
						continue;
					return rightNode;
				}
			} while (true);
		}

		Node SetBucket(uint index, Node node)
		{
			try
			{
				_slim.EnterReadLock();
				CheckSegment(index, true);

				Interlocked.CompareExchange(ref _buckets[index], node, null);
				return _buckets[index];
			}
			finally
			{
				_slim.ExitReadLock();
			}
		}

		class Node
		{
			public T Data;
			public ulong Key;
			public bool Marked;
			public Node Next;
			public TKey SubKey;

			public Node Init(ulong key, TKey subKey, T data)
			{
				Key = key;
				SubKey = subKey;
				Data = data;

				Marked = false;
				Next = null;

				return this;
			}

			// Used to create dummy node
			public Node Init(ulong key)
			{
				Key = key;
				Data = default(T);

				Next = null;
				Marked = false;
				SubKey = default(TKey);

				return this;
			}

			// Used to create marked node
			public Node Init(Node wrapped)
			{
				Marked = true;
				Next = wrapped;

				Key = 0;
				Data = default(T);
				SubKey = default(TKey);

				return this;
			}
		}

		struct SimpleRwLock
		{
			const int RwWait = 1;
			const int RwWrite = 2;
			const int RwRead = 4;

			int _rwlock;

			public void EnterReadLock()
			{
				var sw = new SpinWait();
				do
				{
					while ((_rwlock & (RwWrite | RwWait)) > 0)
						sw.SpinOnce();

					if ((Interlocked.Add(ref _rwlock, RwRead) & (RwWait | RwWait)) == 0)
						return;

					Interlocked.Add(ref _rwlock, -RwRead);
				} while (true);
			}

			public void ExitReadLock()
			{
				Interlocked.Add(ref _rwlock, -RwRead);
			}

			public void EnterWriteLock()
			{
				var sw = new SpinWait();
				do
				{
					int state = _rwlock;
					if (state < RwWrite)
					{
						if (Interlocked.CompareExchange(ref _rwlock, RwWrite, state) == state)
							return;
						state = _rwlock;
					}
					// We register our interest in taking the Write lock (if upgradeable it's already done)
					while ((state & RwWait) == 0 && Interlocked.CompareExchange(ref _rwlock, state | RwWait, state) != state)
						state = _rwlock;
					// Before falling to sleep
					while (_rwlock > RwWait)
						sw.SpinOnce();
				} while (true);
			}

			public void ExitWriteLock()
			{
				Interlocked.Add(ref _rwlock, -RwWrite);
			}
		}
	}
}