Move transitiveClosure into :commonizer-api

2021-03-26 10:30:02 +01:00
parent 35e1f8a520
commit 47f36c04fc
4 changed files with 13 additions and 11 deletions
@@ -0,0 +1,40 @@
+/*
+ * Copyright 2010-2021 JetBrains s.r.o. and Kotlin Programming Language contributors.
+ * Use of this source code is governed by the Apache 2.0 license that can be found in the license/LICENSE.txt file.
+ */
+
+package org.jetbrains.kotlin.commonizer.util
+
+/**
+ * General purpose implementation of a transitive closure
+ * - Recursion free
+ * - Predictable amount of allocations
+ * - Handles loops and self references gracefully
+ * @param edges: Producer function from one node to all its children. This implementation can handle loops and self references gracefully.
+ * @return Note: No guarantees given about the order ot this [Set]
+ */
+public inline fun <reified T> transitiveClosure(seed: T, edges: T.() -> Iterable<T>): Set<T> {
+    // Fast path when initial edges are empty
+    val initialEdges = seed.edges()
+    if (initialEdges is Collection && initialEdges.isEmpty()) return emptySet()
+
+    val queue = deque<T>()
+    val results = mutableSetOf<T>()
+    queue.addAll(initialEdges)
+    while (queue.isNotEmpty()) {
+        // ArrayDeque implementation will optimize this call to 'removeFirst'
+        val resolved = queue.removeAt(0)
+        if (resolved != seed && results.add(resolved)) {
+            queue.addAll(resolved.edges())
+        }
+    }
+
+    return results.toSet()
+}
+
+@OptIn(ExperimentalStdlibApi::class)
+@PublishedApi
+internal inline fun <reified T> deque(): MutableList<T> {
+    return if (KotlinVersion.CURRENT.isAtLeast(1, 4)) ArrayDeque()
+    else mutableListOf()
+}