1 files changed, 57 insertions, 0 deletions
diff --git a/src/main/kotlin/util/collections/InstanceList.kt b/src/main/kotlin/util/collections/InstanceList.kt
new file mode 100644
index 0000000..fd8c786
--- /dev/null
+++ b/src/main/kotlin/util/collections/InstanceList.kt
@@ -0,0 +1,57 @@
+package moe.nea.firmament.util.collections
+
+import java.lang.ref.ReferenceQueue
+import java.lang.ref.WeakReference
+
+class InstanceList<T : Any>(val name: String) {
+    val queue = object : ReferenceQueue<T>() {}
+    val set = mutableSetOf<Ref>()
+
+    val size: Int
+        get() {
+            clearOldReferences()
+            return set.size
+        }
+
+    fun clearOldReferences() {
+        while (true) {
+            val reference = queue.poll() ?: break
+            set.remove(reference)
+        }
+    }
+
+    fun getAll(): List<T> {
+        clearOldReferences()
+        return set.mapNotNull { it.get() }
+    }
+
+    fun add(t: T) {
+        set.add(Ref(t))
+    }
+
+    init {
+        if (init)
+            allInstances.add(this)
+    }
+
+    inner class Ref(referent: T) : WeakReference<T>(referent) {
+        val hashCode = System.identityHashCode(referent)
+        override fun equals(other: Any?): Boolean {
+            return other is InstanceList<*>.Ref && hashCode == other.hashCode && get() === other.get()
+        }
+
+        override fun hashCode(): Int {
+            return hashCode
+        }
+    }
+
+    companion object {
+        private var init = false
+        val allInstances = InstanceList<InstanceList<*>>("InstanceLists")
+
+        init {
+            init = true
+            allInstances.add(allInstances)
+        }
+    }
+}