stgsharp/StgSharp.Common/HighPerformance/Memory/HLSFAllocator.BucketNode.cs

//-----------------------------------------------------------------------
// -----------------------------------------------------------------------
// file="HLSFAllocator.BucketNode"
// Project: StgSharp
// AuthorGroup: Nitload
// Copyright (c) Nitload. All rights reserved.
//     
// 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
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// furnished to do so, subject to the following conditions:
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// The above copyright notice and this permission notice shall be included in all
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// FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
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// -----------------------------------------------------------------------
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using System;
using System.Reflection.Metadata;
using System.Runtime.CompilerServices;
using System.Runtime.InteropServices;

namespace StgSharp.HighPerformance.Memory
{
    public unsafe partial class HybridLayerSegregatedFitAllocator
    {

        #region BucketNode Operations

        [MethodImpl(MethodImplOptions.AggressiveInlining)]
        private static bool IsNullOrEmpty(BucketNode* node)
        {
            return node == null;
        }

            #endregion

        private void PushLevel(int levelIndex, int sizeIndex, BucketNode* node)
        {
            if (node == null || node->EntryRef == null) {
                return;
            }

            Index index = (levelIndex > MaxLevel) ? ^1 : (3 * levelIndex) + sizeIndex;
            if (_bucketHeads[index] == (BucketNode*)null)
            {
                _bucketHeads[index] = node;
                node->IsInBucket = true;
                node->NextLevel = null;
                node->PreviousLevel = null;

                // Console.WriteLine($"Push to empty level of {levelIndex} {sizeIndex}, bucket pos {(ulong)node}");
                return;
            } else
            {
                BucketNode* head = _bucketHeads[index];
                node->NextLevel = head;
                BucketNode* headNode = head;
                node->IsInBucket = true;
                _bucketHeads[index] = node;

                // Console.WriteLine($"Push to head of level of {levelIndex} {sizeIndex}, bucket pos {(ulong)node}, previous head is at {head}");
                if (headNode != null)
                {
                    headNode->PreviousLevel = node;
                }
                return;
            }
        }

        private void RemoveFromBucket(int levelIndex, int sizeIndex, BucketNode* node)
        {
            Index index = (levelIndex > MaxLevel) ? ^1 : (3 * levelIndex) + sizeIndex;

            if (_bucketHeads[index] == node)
            {
                if (TryPopLevel(levelIndex, sizeIndex, out _)) {
                    return;
                }
            }

            BucketNode* previous = node->PreviousLevel;
            BucketNode* next = node->NextLevel;

            if (previous != null) {
                previous->NextLevel = next;
            }
            if (next != null) {
                next->PreviousLevel = previous;
            }

            node->NextLevel = (BucketNode*)null;
            node->PreviousLevel = (BucketNode*)null;
            node->IsInBucket = false;
            return;
        }

        private bool TryPopLevel(int levelIndex, int sizeIndex, out BucketNode* node)
        {
            int index = (3 * levelIndex) + sizeIndex;

            BucketNode* head = _bucketHeads[index];

            if (head == null)
            {
                node = null;
                return false;
            }

            // Console.WriteLine($"level popped from level {levelIndex} {sizeIndex}, node is at {(ulong)head}");
            BucketNode* next = head->NextLevel;

            if (next == null)
            {
                _bucketHeads[index] = null;
                node = head;
                return true;
            }
            _bucketHeads[index] = head->NextLevel;
            node = head;
            node->IsInBucket = false;
            node->NextLevel = null;
            if (next != null) {
                next->PreviousLevel = null;
            }
            return true;
        }

        private bool TryRemoveFromBucket(int levelIndex, int sizeIndex, BucketNode* node)
        {
            Index index = levelIndex > 9 ? ^1 : (3 * levelIndex) + sizeIndex;
            if (_bucketHeads[index] == node) {
                return TryPopLevel(levelIndex, sizeIndex, out _);
            }

            BucketNode* previous = node->PreviousLevel;
            BucketNode* next = node->NextLevel;

            if (previous != null) {
                previous->NextLevel = next;
            }
            if (next != null) {
                next->PreviousLevel = previous;
            }

            node->NextLevel = null;
            node->PreviousLevel = null;
            node->IsInBucket = false;
            node->EntryRef = null;

            return true;
        }

        /// <summary>
        ///   BucketNode structure - specialized node for bucket linked lists Stored in main
        ///   allocation area (user-overwritable region)
        /// </summary>
        [StructLayout(LayoutKind.Explicit)]
        internal struct BucketNode
        {

            [FieldOffset(0)] internal Entry* EntryRef;     // Pointer to corresponding Entry
            // [FieldOffset(16)] internal ulong LockBuffer;
            [FieldOffset(8)] internal  BucketNode* NextLevel;     // Bucket stack linked list: next pointer
            [FieldOffset(24)] internal BucketNode* PreviousLevel; // Bucket stack linked list: previous pointer
            [FieldOffset(32)] internal bool IsInBucket;     // Whether in bucket

        }

    }
}