From 40459a7e99615dab09059a40df28bda39f81ce58 Mon Sep 17 00:00:00 2001
From: DBotThePony <dbotthepony@yandex.ru>
Date: Sat, 3 Feb 2024 18:27:52 +0700
Subject: [PATCH] WeakHashSet

---
 .../kommons/collect/ReferenceHashStrategy.kt  | 25 ++++++
 .../kommons/collect/WeakHashSet.kt            | 78 +++++++++++++++++++
 .../kommons/util/HashedWeakReference.kt       | 28 +++++++
 3 files changed, 131 insertions(+)
 create mode 100644 src/main/kotlin/ru/dbotthepony/kommons/collect/ReferenceHashStrategy.kt
 create mode 100644 src/main/kotlin/ru/dbotthepony/kommons/collect/WeakHashSet.kt
 create mode 100644 src/main/kotlin/ru/dbotthepony/kommons/util/HashedWeakReference.kt

diff --git a/src/main/kotlin/ru/dbotthepony/kommons/collect/ReferenceHashStrategy.kt b/src/main/kotlin/ru/dbotthepony/kommons/collect/ReferenceHashStrategy.kt
new file mode 100644
index 0000000..d656a12
--- /dev/null
+++ b/src/main/kotlin/ru/dbotthepony/kommons/collect/ReferenceHashStrategy.kt
@@ -0,0 +1,25 @@
+package ru.dbotthepony.kommons.collect
+
+import it.unimi.dsi.fastutil.Hash
+import java.lang.ref.Reference
+
+object ReferenceHashStrategy : Hash.Strategy<Any?> {
+	override fun equals(a: Any?, b: Any?): Boolean {
+		if (a === b) return true
+		if (a == null || b == null) return false
+
+		if (a is Reference<*>) {
+			val ref = a.get()
+			if (b is Reference<*>) return ref != null && ref == b.get()
+			return ref == b
+		} else if (b is Reference<*>) {
+			return b.get() == a
+		} else {
+			return a == b
+		}
+	}
+
+	override fun hashCode(o: Any?): Int {
+		return o.hashCode()
+	}
+}
diff --git a/src/main/kotlin/ru/dbotthepony/kommons/collect/WeakHashSet.kt b/src/main/kotlin/ru/dbotthepony/kommons/collect/WeakHashSet.kt
new file mode 100644
index 0000000..1fc821a
--- /dev/null
+++ b/src/main/kotlin/ru/dbotthepony/kommons/collect/WeakHashSet.kt
@@ -0,0 +1,78 @@
+package ru.dbotthepony.kommons.collect
+
+import it.unimi.dsi.fastutil.objects.ObjectLinkedOpenCustomHashSet
+import it.unimi.dsi.fastutil.objects.ObjectOpenCustomHashSet
+import it.unimi.dsi.fastutil.objects.ObjectSet
+import ru.dbotthepony.kommons.util.HashedWeakReference
+import java.lang.ref.ReferenceQueue
+
+class WeakHashSet<E : Any>(initialCapacity: Int = 16, loadFactor: Float = 0.75f, linked: Boolean = false) : MutableSet<E> {
+	private val queue = ReferenceQueue<E>()
+	private val backing: ObjectSet<Any> = if (linked) ObjectLinkedOpenCustomHashSet(initialCapacity, loadFactor, ReferenceHashStrategy) else ObjectOpenCustomHashSet(initialCapacity, loadFactor, ReferenceHashStrategy)
+
+	private fun purge() {
+		var next = queue.poll()
+
+		while (next != null) {
+			backing.remove(next)
+			next = queue.poll()
+		}
+	}
+
+	override fun add(element: E): Boolean {
+		purge()
+		if (element in backing) return false
+		return backing.add(HashedWeakReference(element, queue))
+	}
+
+	override fun addAll(elements: Collection<E>): Boolean {
+		var any = false
+		elements.forEach { any = add(it) || any }
+		return any
+	}
+
+	override fun clear() {
+		backing.clear()
+		while (queue.poll() != null) {}
+	}
+
+	override fun iterator(): MutableIterator<E> {
+		purge()
+		return backing.iterator().map { (it as HashedWeakReference<E>).get() }.filterNotNull()
+	}
+
+	override fun remove(element: E): Boolean {
+		purge()
+		return backing.remove(element)
+	}
+
+	override fun removeAll(elements: Collection<E>): Boolean {
+		purge()
+		return backing.removeAll(elements)
+	}
+
+	override fun retainAll(elements: Collection<E>): Boolean {
+		purge()
+		return backing.retainAll(elements)
+	}
+
+	override val size: Int get() {
+		purge()
+		return backing.size
+	}
+
+	override fun contains(element: E): Boolean {
+		purge()
+		return backing.contains(element)
+	}
+
+	override fun containsAll(elements: Collection<E>): Boolean {
+		purge()
+		return backing.containsAll(elements)
+	}
+
+	override fun isEmpty(): Boolean {
+		purge()
+		return backing.isEmpty()
+	}
+}
diff --git a/src/main/kotlin/ru/dbotthepony/kommons/util/HashedWeakReference.kt b/src/main/kotlin/ru/dbotthepony/kommons/util/HashedWeakReference.kt
new file mode 100644
index 0000000..906987f
--- /dev/null
+++ b/src/main/kotlin/ru/dbotthepony/kommons/util/HashedWeakReference.kt
@@ -0,0 +1,28 @@
+package ru.dbotthepony.kommons.util
+
+import java.lang.ref.ReferenceQueue
+import java.lang.ref.WeakReference
+
+/**
+ * [WeakReference], but with [hashCode] overridden with hash of referent object
+ */
+@Suppress("EqualsOrHashCode")
+class HashedWeakReference<T : Any> : WeakReference<T> {
+	constructor(value: T) : super(value) {
+		hash = value.hashCode()
+	}
+
+	constructor(value: T, queue: ReferenceQueue<T>) : super(value, queue) {
+		hash = value.hashCode()
+	}
+
+	private val hash: Int
+
+	override fun hashCode(): Int {
+		return hash
+	}
+
+	override fun toString(): String {
+		return "HashedWeakReference[hash=$hash]"
+	}
+}