PS: Copy extractor and various scripts from internal repo to public repo.

powershell/extractor/Semmle.Extraction.PowerShell/CachedFunction.cs

@@ -0,0 +1,68 @@
+using System;
+using System.Collections.Generic;
+
+namespace Semmle.Extraction.PowerShell
+{
+    /// <summary>
+    /// A factory and a cache for mapping source entities to target entities.
+    /// Could be considered as a memoizer.
+    /// </summary>
+    /// <typeparam name="TSrc">The type of the source.</typeparam>
+    /// <typeparam name="TTarget">The type of the generated object.</typeparam>
+    public class CachedFunction<TSrc, TTarget> where TSrc : notnull
+    {
+        private readonly Func<TSrc, TTarget> generator;
+        private readonly Dictionary<TSrc, TTarget> cache;
+
+        /// <summary>
+        /// Initializes the factory with a given mapping.
+        /// </summary>
+        /// <param name="g">The mapping.</param>
+        public CachedFunction(Func<TSrc, TTarget> g)
+        {
+            generator = g;
+            cache = new Dictionary<TSrc, TTarget>();
+        }
+
+        /// <summary>
+        /// Gets the target for a given source.
+        /// Create it if it does not exist.
+        /// </summary>
+        /// <param name="src">The source object.</param>
+        /// <returns>The created object.</returns>
+        public TTarget this[TSrc src]
+        {
+            get
+            {
+                if (!cache.TryGetValue(src, out var result))
+                {
+                    result = generator(src);
+                    cache[src] = result;
+                }
+                return result;
+            }
+        }
+    }
+
+    /// <summary>
+    /// A factory for mapping a pair of source entities to a target entity.
+    /// </summary>
+    /// <typeparam name="TSrcEntity1">Source entity type 1.</typeparam>
+    /// <typeparam name="TSrcEntity2">Source entity type 2.</typeparam>
+    /// <typeparam name="TTarget">The target type.</typeparam>
+    public class CachedFunction<TSrcEntity1, TSrcEntity2, TTarget>
+    {
+        private readonly CachedFunction<(TSrcEntity1, TSrcEntity2), TTarget> factory;
+
+        /// <summary>
+        /// Initializes the factory with a given mapping.
+        /// </summary>
+        /// <param name="g">The mapping.</param>
+        public CachedFunction(Func<TSrcEntity1, TSrcEntity2, TTarget> g)
+        {
+            factory = new CachedFunction<(TSrcEntity1, TSrcEntity2), TTarget>(p => g(p.Item1, p.Item2));
+        }
+
+        public TTarget this[TSrcEntity1 s1, TSrcEntity2 s2] => factory[(s1, s2)];
+    }
+}