Add readonly Capacity property to PriorityQueue<TElement, TPriority> (#…

…110727) * Add readonly Capacity property to PriorityQueue<TElement, TPriority> * Add test for EnsureCapacity and TrimExcess * remove param * Update src/libraries/System.Collections/tests/Generic/PriorityQueue/PriorityQueue.Generic.Tests.cs Co-authored-by: Stephen Toub <[email protected]> * Update src/libraries/System.Collections/tests/Generic/PriorityQueue/PriorityQueue.Generic.Tests.cs Co-authored-by: Stephen Toub <[email protected]> * Update src/libraries/System.Collections/src/System/Collections/Generic/PriorityQueue.cs Co-authored-by: Stephen Toub <[email protected]> --------- Co-authored-by: Stephen Toub <[email protected]>
dotnet · Jan 22, 2025 · 4dabc7b · 4dabc7b
1 parent 4758103
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diff --git a/src/libraries/System.Collections/ref/System.Collections.cs b/src/libraries/System.Collections/ref/System.Collections.cs
@@ -287,6 +287,7 @@ public PriorityQueue(int initialCapacity) { }
         public PriorityQueue(int initialCapacity, System.Collections.Generic.IComparer<TPriority>? comparer) { }
         public System.Collections.Generic.IComparer<TPriority> Comparer { get { throw null; } }
         public int Count { get { throw null; } }
+        public int Capacity { get { throw null; } }
         public System.Collections.Generic.PriorityQueue<TElement, TPriority>.UnorderedItemsCollection UnorderedItems { get { throw null; } }
         public void Clear() { }
         public TElement Dequeue() { throw null; }

diff --git a/src/libraries/System.Collections/src/System/Collections/Generic/PriorityQueue.cs b/src/libraries/System.Collections/src/System/Collections/Generic/PriorityQueue.cs
@@ -171,6 +171,11 @@ public PriorityQueue(IEnumerable<(TElement Element, TPriority Priority)> items,
         /// </summary>
         public int Count => _size;
 
+        /// <summary>
+        ///  Gets the total numbers of elements the queue's backing storage can hold without resizing.
+        /// </summary>
+        public int Capacity => _nodes.Length;
+
         /// <summary>
         ///  Gets the priority comparer used by the <see cref="PriorityQueue{TElement, TPriority}"/>.
         /// </summary>

diff --git a/src/libraries/System.Collections/tests/Generic/PriorityQueue/PriorityQueue.Generic.Tests.cs b/src/libraries/System.Collections/tests/Generic/PriorityQueue/PriorityQueue.Generic.Tests.cs
@@ -34,6 +34,28 @@ protected PriorityQueue<TElement, TPriority> CreatePriorityQueue(
             return queue;
         }
 
+        [Theory]
+        [InlineData(1)]
+        [InlineData(100)]
+        public void CreateWithCapacity_EqualsCapacityProperty(int capacity)
+        {
+            var queue = new PriorityQueue<TElement, TPriority>(capacity);
+            Assert.Equal(capacity, queue.Capacity);
+        }
+
+        [Fact]
+        public void PriorityQueue_EnsureCapacityThenTrimExcess_CapacityUpdates()
+        {
+            var queue = new PriorityQueue<TElement, TPriority>(2);
+            Assert.Equal(2, queue.Capacity);
+
+            queue.EnsureCapacity(12);
+            Assert.InRange(queue.Capacity, 12, int.MaxValue);
+
+            queue.TrimExcess();
+            Assert.Equal(0, queue.Capacity);
+        }
+
         #endregion
 
         #region Constructors