SplitOrderedList.cs

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// 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.
//
//

#if NET_4_0 || INSIDE_SYSTEM_WEB

using System;
using System.Threading;
using System.Collections;
using System.Collections.Generic;
using System.Runtime.Serialization;

namespace System.Collections.Concurrent
{
    internal class SplitOrderedList<TKey, T>
    {
        class Node
        {
            public bool Marked;
            public ulong Key;
            public TKey SubKey;
            public T Data;
            public Node Next;

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

                this.Marked = false;
                this.Next = null;

                return this;
            }

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

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

                return this;
            }

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

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

                return this;
            }
        }

        const int MaxLoad = 5;
        const uint BucketSize = 512;

        Node head;
        Node tail;

        Node[] buckets = new Node [BucketSize];
        int count;
        int size = 2;

        SimpleRwLock slim = new SimpleRwLock ();

        readonly IEqualityComparer<TKey> comparer;

        public SplitOrderedList (IEqualityComparer<TKey> comparer)
        {
            this.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 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;
        }
        
        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;
        }

        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;
        }
        
        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 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 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;
            }
        }

        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);
        }
        
        // Turn v's MSB off
        static uint GetParent (uint v)
        {
            uint t, tt;
            
            // Find MSB position in v
            var 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));
        }

        // Reverse integer bits and make sure LSB is set
        static ulong ComputeRegularKey (uint key)
        {
            return ComputeDummyKey (key) | 1;
        }
        
        // 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) |
                            ((uint)reverseTable[(key >> 24) & 0xff]))) << 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];
        }

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

                AotInterlocked.CompareExchange (ref buckets[index], node, null);
                return buckets[index];
            } finally {
                slim.ExitReadLock ();
            }
        }

        // 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 ();
        }

        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;
                    else 
                        return rightNode;
                }
                
                if (AotInterlocked.CompareExchange (ref left.Next, rightNode, leftNodeNext) == leftNodeNext) {
                    if (rightNode != tail && rightNode.Next.Marked)
                        continue;
                    else
                        return rightNode;
                }
            } while (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 (AotInterlocked.CompareExchange (ref rightNode.Next, markedNode, rightNodeNext) == rightNodeNext)
                        break;
                }
            } while (true);
            
            if (AotInterlocked.CompareExchange (ref leftNode.Next, rightNodeNext, rightNode) != rightNode)
                ListSearch (rightNode.Key, subKey, ref leftNode, startPoint);
            
            return true;
        }
        
        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 (AotInterlocked.CompareExchange (ref leftNode.Next, newNode, rightNode) == rightNode)
                    return true;
            } while (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);
        }

        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
        };

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

            int rwlock;

            public void EnterReadLock ()
            {
                SpinWait 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 ()
            {
                SpinWait 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);
            }
        }
    }

#if INSIDE_SYSTEM_WEB && !NET_4_0
    internal struct SpinWait
    {
        // The number of step until SpinOnce yield on multicore machine
        const           int  step = 10;
        const           int  maxTime = 200;
        static readonly bool isSingleCpu = (Environment.ProcessorCount == 1);

        int ntime;

        public void SpinOnce ()
        {
            ntime += 1;

            if (isSingleCpu) {
                // On a single-CPU system, spinning does no good
                Thread.Sleep (0);
            } else {
                if (ntime % step == 0)
                    Thread.Sleep (0);
                else
                    // Multi-CPU system might be hyper-threaded, let other thread run
                    Thread.SpinWait (Math.Min (ntime, maxTime) << 1);
            }
        }
    }
#endif
}

#endif