MulAvailable

StgSharp.Common/Collections/CapacityFixedStack.cs

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+//-----------------------------------------------------------------------
+// -----------------------------------------------------------------------
+// file="CapacityFixedStack"
+// 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
+// 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;
+using System.Collections.Generic;
+using System.Runtime.CompilerServices;
+using System.Threading;
+
+namespace StgSharp.Collections
+{
+    [CollectionBuilder(typeof(CapacityFixedStackBuilder), nameof(CapacityFixedStackBuilder.Create))]
+    public class CapacityFixedStack<T> : IEnumerable<T>
+    {
+
+        private readonly T[] _values;
+
+        // _index points to the next free slot (top empty position). Therefore Count == _index.
+        private int _index;
+
+        public CapacityFixedStack(int size)
+        {
+            ArgumentOutOfRangeException.ThrowIfNegative(size);
+            _values = new T[size];
+            _index = 0; // empty stack
+        }
+
+        public T? First => Volatile.Read(ref _index) > 0 ? _values[0] : default;
+
+        public bool IsEmpty => Volatile.Read(ref _index) == 0;
+
+        public int Count => Volatile.Read(ref _index);
+
+        public int Capacity => _values.Length;
+
+        public ReadOnlySpan<T> AsSpan() => _values.AsSpan(0, _index);
+
+        public void Clear()
+        {
+            if (_index > 0)
+            {
+                Array.Clear(_values, 0, _index);
+                _index = 0;
+            }
+        }
+
+        public IEnumerator<T> GetEnumerator()
+        {
+            for (int i = _index - 1; i >= 0; i--) {
+                yield return _values[i];
+            }
+        }
+
+        public T Peek()
+        {
+            if (_index == 0) {
+                throw new InvalidOperationException("Stack is empty.");
+            }
+            return _values[_index - 1];
+        }
+
+        public T Pop()
+        {
+            if (_index == 0) {
+                throw new InvalidOperationException("Stack is empty.");
+            }
+            _index--;
+            T item = _values[_index];
+            _values[_index] = default!; // Clear reference for GC
+            return item;
+        }
+
+        [MethodImpl(MethodImplOptions.AggressiveInlining)]
+        public T[] PopRange(int count)
+        {
+            if (count <= 0 || _index == 0) {
+                return Array.Empty<T>();
+            }
+            int n = Math.Min(count, _index);
+            int start = _index - n;
+            T[] ret = new T[n];
+            Array.Copy(_values, start, ret, 0, n);
+            Array.Clear(_values, start, n);
+            _index -= n;
+            return ret;
+        }
+
+        public void Push(T item)
+        {
+            if (_index >= _values.Length) {
+                throw new InvalidOperationException("Stack is full.");
+            }
+            _values[_index] = item;
+            _index++;
+        }
+
+        public void PushRange(ReadOnlySpan<T> span)
+        {
+            if (span.Length == 0) {
+                return;
+            }
+            if (_index + span.Length > _values.Length) {
+                throw new InvalidOperationException("Not enough space in the stack to push the entire span.");
+            }
+            span.CopyTo(_values.AsSpan(_index, span.Length));
+            _index += span.Length;
+        }
+
+        public bool TryPop(out T value)
+        {
+            if (_index == 0)
+            {
+                value = default!;
+                return false;
+            }
+            _index--;
+            value = _values[_index];
+            _values[_index] = default!;
+            return true;
+        }
+
+        [MethodImpl(MethodImplOptions.AggressiveInlining)]
+        internal Span<T> GetValueLayout()
+        {
+            return _values.AsSpan();
+        }
+
+        IEnumerator IEnumerable.GetEnumerator()
+        {
+            return GetEnumerator();
+        }
+
+    }
+
+    public static class CapacityFixedStackBuilder
+    {
+
+        public static CapacityFixedStack<T> Create<T>(ReadOnlySpan<T> values)
+        {
+            CapacityFixedStack<T> stack = new(values.Length);
+            stack.PushRange(values); // Push in order
+            return stack;
+        }
+
+    }
+}