Экспериментальный самодельный StringInterner

src/main/kotlin/ru/dbotthepony/kstarbound/Starbound.kt

@@ -5,7 +5,9 @@ import com.github.benmanes.caffeine.cache.Caffeine
 import com.github.benmanes.caffeine.cache.Interner
 import com.google.gson.*
 import com.google.gson.internal.bind.JsonTreeReader
+import it.unimi.dsi.fastutil.Hash
 import it.unimi.dsi.fastutil.objects.Object2ObjectFunction
+import it.unimi.dsi.fastutil.objects.Object2ObjectOpenCustomHashMap
 import it.unimi.dsi.fastutil.objects.Object2ObjectOpenHashMap
 import org.apache.logging.log4j.LogManager
 import org.lwjgl.stb.STBImage
@@ -70,6 +72,7 @@ import ru.dbotthepony.kstarbound.util.WriteOnce
 import ru.dbotthepony.kstarbound.util.traverseJsonPath
 import ru.dbotthepony.kvector.vector.nint.Vector2i
 import java.io.*
+import java.lang.ref.ReferenceQueue
 import java.lang.ref.WeakReference
 import java.text.DateFormat
 import java.time.Duration
@@ -805,3 +808,75 @@ class Starbound : ISBFileLocator {
 		private val polyfill by lazy { loadInternalScript("polyfill") }
 	}
 }
+
+private class StringInterner(private val segmentBits: Int) : Interner<String>, Hash.Strategy<Any> {
+	class Ref(referent: String, queue: ReferenceQueue<String>) : WeakReference<String>(referent, queue) {
+		val hash = referent.hashCode()
+
+		override fun hashCode(): Int {
+			return hash
+		}
+	}
+
+	override fun equals(a: Any?, b: Any?): Boolean {
+		if (a is String && b is Ref) return a == b.get()
+		if (a is Ref && b is String) return a.get() == b
+		return a === b
+	}
+
+	override fun hashCode(o: Any): Int {
+		return o.hashCode()
+	}
+
+	private val queue = ReferenceQueue<String>()
+	private val actualSegmentBits: Int
+
+	init {
+		var result = 0
+
+		for (i in 0 until segmentBits) {
+			result = result or (1.shl(i))
+		}
+
+		actualSegmentBits = result
+	}
+
+	private val cleaner = Runnable {
+		while (true) {
+			val ref = queue.remove() as Ref
+			val segment = segments[ref.hash and actualSegmentBits]
+
+			synchronized(segment) {
+				val removed = segment.remove(ref)
+				check(removed === ref) { "Expected to remove reference $ref from segment ${ref.hash and actualSegmentBits} (full hash: ${ref.hash}), but we removed $removed (removed hash: ${removed.hashCode()}, removed segment: ${removed.hashCode() and actualSegmentBits})" }
+			}
+		}
+	}
+
+	private val thread = Thread(cleaner, "String Interner Cleanup Thread")
+
+	init {
+		thread.priority = 2
+		thread.isDaemon = true
+		thread.start()
+	}
+
+	private val segments: Array<Object2ObjectOpenCustomHashMap<Any, Any>> = Array(1.shl(segmentBits)) { Object2ObjectOpenCustomHashMap(this) }
+
+	override fun intern(sample: String): String {
+		val hash = sample.hashCode()
+		val segment = segments[hash and actualSegmentBits]
+
+		synchronized(segment) {
+			val canonical = (segment[sample] as Ref?)?.get()
+
+			if (canonical != null) {
+				return canonical
+			}
+
+			val ref = Ref(sample, queue)
+			segment.put(ref, ref)
+			return sample
+		}
+	}
+}