Merge pull request #1529 from alistair/xmlreader_read_to_next_sibling_bug

[mono.git] / mcs / class / System.Web / System.Collections.Concurrent / 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.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);

                                Interlocked.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 (Interlocked.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 (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 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);
                }
                
                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);
                        }
                }
        }

}