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Assets/Plugins/Animancer/Internal/Editor/ConversionCache.cs

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+// Animancer // https://kybernetik.com.au/animancer // Copyright 2018-2023 Kybernetik //
+
+#if UNITY_EDITOR
+
+//#define ANIMANCER_LOG_CONVERSION_CACHE
+
+using System;
+using System.Collections.Generic;
+using UnityEngine;
+
+namespace Animancer.Editor
+{
+    /// <summary>[Editor-Only]
+    /// A simple system for converting objects and storing the results so they can be reused to minimise the need for
+    /// garbage collection, particularly for string construction.
+    /// </summary>
+    /// <remarks>This class doesn't use any Editor-Only functionality, but it's unlikely to be useful at runtime.</remarks>
+    /// https://kybernetik.com.au/animancer/api/Animancer.Editor/ConversionCache_2
+    /// 
+    public class ConversionCache<TKey, TValue>
+    {
+        /************************************************************************************************************************/
+
+        private class CachedValue
+        {
+            public int lastFrameAccessed;
+            public TValue value;
+        }
+
+        /************************************************************************************************************************/
+
+        private readonly Dictionary<TKey, CachedValue>
+            Cache = new Dictionary<TKey, CachedValue>();
+        private readonly List<TKey>
+            Keys = new List<TKey>();
+        private readonly Func<TKey, TValue>
+            Converter;
+
+        private int _LastCleanupFrame;
+
+        /************************************************************************************************************************/
+
+        /// <summary>
+        /// Creates a new <see cref="ConversionCache{TKey, TValue}"/> which uses the specified delegate to convert values.
+        /// </summary>
+        public ConversionCache(Func<TKey, TValue> converter) => Converter = converter;
+
+        /************************************************************************************************************************/
+
+        /// <summary>
+        /// If a value has already been cached for the specified `key`, return it. Otherwise create a new one using
+        /// the delegate provided in the constructor and cache it.
+        /// <para></para>
+        /// If the `key` is <c>null</c>, this method returns the default <typeparamref name="TValue"/>.
+        /// </summary>
+        /// <remarks>This method also periodically removes values that have not been used recently.</remarks>
+        public TValue Convert(TKey key)
+        {
+            if (key == null)
+                return default;
+
+            CachedValue cached;
+
+            // The next time a value is retrieved after at least 100 frames, clear out any old ones.
+            var frame = Time.frameCount;
+            if (_LastCleanupFrame + 100 < frame)
+            {
+
+                for (int i = Keys.Count - 1; i >= 0; i--)
+                {
+                    var checkKey = Keys[i];
+                    if (!Cache.TryGetValue(checkKey, out cached) ||
+                        cached.lastFrameAccessed <= _LastCleanupFrame)
+                    {
+                        Cache.Remove(checkKey);
+                        Keys.RemoveAt(i);
+                    }
+                }
+
+                _LastCleanupFrame = frame;
+
+            }
+
+            if (!Cache.TryGetValue(key, out cached))
+            {
+                Cache.Add(key, cached = new CachedValue { value = Converter(key) });
+                Keys.Add(key);
+
+            }
+
+            cached.lastFrameAccessed = frame;
+
+            return cached.value;
+        }
+
+        /************************************************************************************************************************/
+    }
+}
+
+#endif
+