Firstborn/Library/PackageCache/com.unity.render-pipelines.universal@12.1.8/Runtime/External/LibTessDotNet/PriorityQueue.cs

/*
** SGI FREE SOFTWARE LICENSE B (Version 2.0, Sept. 18, 2008)
** Copyright (C) 2011 Silicon Graphics, Inc.
** 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
** 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 including the dates of first publication and either this
** permission notice or a reference to http://oss.sgi.com/projects/FreeB/ 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 SILICON GRAPHICS, INC.
** 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.
**
** Except as contained in this notice, the name of Silicon Graphics, Inc. shall not
** be used in advertising or otherwise to promote the sale, use or other dealings in
** this Software without prior written authorization from Silicon Graphics, Inc.
*/
/*
** Original Author: Eric Veach, July 1994.
** libtess2: Mikko Mononen, http://code.google.com/p/libtess2/.
** LibTessDotNet: Remi Gillig, https://github.com/speps/LibTessDotNet
*/

using System;
using System.Collections.Generic;
using System.Diagnostics;

namespace UnityEngine.Rendering.Universal
{
    namespace LibTessDotNet
    {
        internal class PriorityQueue<TValue> where TValue : class
        {
            private PriorityHeap<TValue>.LessOrEqual _leq;
            private PriorityHeap<TValue> _heap;
            private TValue[] _keys;
            private int[] _order;

            private int _size, _max;
            private bool _initialized;

            public bool Empty { get { return _size == 0 && _heap.Empty; } }

            public PriorityQueue(int initialSize, PriorityHeap<TValue>.LessOrEqual leq)
            {
                _leq = leq;
                _heap = new PriorityHeap<TValue>(initialSize, leq);

                _keys = new TValue[initialSize];

                _size = 0;
                _max = initialSize;
                _initialized = false;
            }

            class StackItem
            {
                internal int p, r;
            };

            static void Swap(ref int a, ref int b)
            {
                int tmp = a;
                a = b;
                b = tmp;
            }

            public void Init()
            {
                var stack = new Stack<StackItem>();
                int p, r, i, j, piv;
                uint seed = 2016473283;

                p = 0;
                r = _size - 1;
                _order = new int[_size + 1];
                for (piv = 0, i = p; i <= r; ++piv, ++i)
                {
                    _order[i] = piv;
                }

                stack.Push(new StackItem { p = p, r = r });
                while (stack.Count > 0)
                {
                    var top = stack.Pop();
                    p = top.p;
                    r = top.r;

                    while (r > p + 10)
                    {
                        seed = seed * 1539415821 + 1;
                        i = p + (int)(seed % (r - p + 1));
                        piv = _order[i];
                        _order[i] = _order[p];
                        _order[p] = piv;
                        i = p - 1;
                        j = r + 1;
                        do
                        {
                            do { ++i; } while (!_leq(_keys[_order[i]], _keys[piv]));
                            do { --j; } while (!_leq(_keys[piv], _keys[_order[j]]));
                            Swap(ref _order[i], ref _order[j]);
                        }
                        while (i < j);
                        Swap(ref _order[i], ref _order[j]);
                        if (i - p < r - j)
                        {
                            stack.Push(new StackItem { p = j + 1, r = r });
                            r = i - 1;
                        }
                        else
                        {
                            stack.Push(new StackItem { p = p, r = i - 1 });
                            p = j + 1;
                        }
                    }
                    for (i = p + 1; i <= r; ++i)
                    {
                        piv = _order[i];
                        for (j = i; j > p && !_leq(_keys[piv], _keys[_order[j - 1]]); --j)
                        {
                            _order[j] = _order[j - 1];
                        }
                        _order[j] = piv;
                    }
                }

#if DEBUG
                p = 0;
                r = _size - 1;
                for (i = p; i < r; ++i)
                {
                    Debug.Assert(_leq(_keys[_order[i + 1]], _keys[_order[i]]), "Wrong sort");
                }
#endif

                _max = _size;
                _initialized = true;
                _heap.Init();
            }

            public PQHandle Insert(TValue value)
            {
                if (_initialized)
                {
                    return _heap.Insert(value);
                }

                int curr = _size;
                if (++_size >= _max)
                {
                    _max <<= 1;
                    Array.Resize(ref _keys, _max);
                }

                _keys[curr] = value;
                return new PQHandle { _handle = -(curr + 1) };
            }

            public TValue ExtractMin()
            {
                Debug.Assert(_initialized);

                if (_size == 0)
                {
                    return _heap.ExtractMin();
                }
                TValue sortMin = _keys[_order[_size - 1]];
                if (!_heap.Empty)
                {
                    TValue heapMin = _heap.Minimum();
                    if (_leq(heapMin, sortMin))
                        return _heap.ExtractMin();
                }
                do
                {
                    --_size;
                }
                while (_size > 0 && _keys[_order[_size - 1]] == null);

                return sortMin;
            }

            public TValue Minimum()
            {
                Debug.Assert(_initialized);

                if (_size == 0)
                {
                    return _heap.Minimum();
                }
                TValue sortMin = _keys[_order[_size - 1]];
                if (!_heap.Empty)
                {
                    TValue heapMin = _heap.Minimum();
                    if (_leq(heapMin, sortMin))
                        return heapMin;
                }
                return sortMin;
            }

            public void Remove(PQHandle handle)
            {
                Debug.Assert(_initialized);

                int curr = handle._handle;
                if (curr >= 0)
                {
                    _heap.Remove(handle);
                    return;
                }
                curr = -(curr + 1);
                Debug.Assert(curr < _max && _keys[curr] != null);

                _keys[curr] = null;
                while (_size > 0 && _keys[_order[_size - 1]] == null)
                {
                    --_size;
                }
            }
        }
    }
}