Fast implementation of some methods in EnhancedContainer

src/main/kotlin/ru/dbotthepony/mc/otm/container/EnhancedContainer.kt

@@ -1,5 +1,6 @@
 package ru.dbotthepony.mc.otm.container
 
+import it.unimi.dsi.fastutil.ints.IntCollection
 import it.unimi.dsi.fastutil.ints.IntOpenHashSet
 import net.minecraft.core.HolderLookup.Provider
 import net.minecraft.nbt.CompoundTag
@@ -12,9 +13,14 @@ import net.minecraft.world.entity.player.Player
 import net.minecraft.world.item.ItemStack
 import net.neoforged.neoforge.common.util.INBTSerializable
 import org.apache.logging.log4j.LogManager
+import ru.dbotthepony.kommons.collect.iterateClearBits
+import ru.dbotthepony.kommons.collect.iterateSetBits
 import ru.dbotthepony.mc.otm.container.slotted.SlottedContainer
+import ru.dbotthepony.mc.otm.core.collect.IntRange2Set
+import ru.dbotthepony.mc.otm.core.collect.map
 import ru.dbotthepony.mc.otm.core.isNotEmpty
 import ru.dbotthepony.mc.otm.core.nbt.set
+import java.util.BitSet
 
 /**
  * Flexible base implementation of [IEnhancedContainer], designed to be inherited, or used as-is
@@ -26,6 +32,55 @@ import ru.dbotthepony.mc.otm.core.nbt.set
 abstract class EnhancedContainer<out S : IContainerSlot>(private val size: Int) : IEnhancedContainer<S>, INBTSerializable<CompoundTag> {
 	private val items = Array(size) { ItemStack.EMPTY }
 	private val observedItems = Array(size) { ItemStack.EMPTY }
+	private val bitmap = BitSet(size)
+
+	final override fun isEmpty(): Boolean {
+		return bitmap.isEmpty
+	}
+
+	final override fun nextEmptySlot(startIndex: Int): Int {
+		if (startIndex >= size)
+			return -1
+		else if (startIndex < 0)
+			return bitmap.nextClearBit(0)
+		else
+			return bitmap.nextClearBit(startIndex)
+	}
+
+	final override fun nextNonEmptySlot(startIndex: Int): Int {
+		if (startIndex >= size)
+			return -1
+		else if (startIndex < 0)
+			return bitmap.nextSetBit(0)
+		else
+			return bitmap.nextSetBit(startIndex)
+	}
+
+	final override fun iterator(): Iterator<ItemStack> {
+		return bitmap.iterateSetBits(size).map { this[it] }
+	}
+
+	final override fun nonEmptySlotIndexIterator(): IntIterator {
+		return bitmap.iterateSetBits(size)
+	}
+
+	final override fun emptySlotIndexIterator(): IntIterator {
+		return bitmap.iterateClearBits(size)
+	}
+
+	final override fun emptySlotIndexIterator(allowedSlots: IntCollection): IntIterator {
+		if (allowedSlots is IntRange2Set && allowedSlots.isNotEmpty())
+			return bitmap.iterateClearBits(allowedSlots.firstInt(), allowedSlots.lastInt() + 1)
+
+		return super.emptySlotIndexIterator(allowedSlots)
+	}
+
+	final override fun nonEmptySlotIndexIterator(allowedSlots: IntCollection): IntIterator {
+		if (allowedSlots is IntRange2Set && allowedSlots.isNotEmpty())
+			return bitmap.iterateSetBits(allowedSlots.firstInt(), allowedSlots.lastInt() + 1)
+
+		return super.nonEmptySlotIndexIterator(allowedSlots)
+	}
 
 	protected open fun notifySlotChanged(slot: Int, old: ItemStack) {}
 
@@ -36,9 +91,11 @@ abstract class EnhancedContainer<out S : IContainerSlot>(private val size: Int)
 			if (items[slot].isEmpty) {
 				items[slot] = ItemStack.EMPTY
 				observedItems[slot] = ItemStack.EMPTY
+				bitmap[slot] = false
 			} else {
 				notifySlotChanged(slot, observedItems[slot])
 				observedItems[slot] = items[slot].copy()
+				bitmap[slot] = true
 			}
 		}
 	}
@@ -50,6 +107,7 @@ abstract class EnhancedContainer<out S : IContainerSlot>(private val size: Int)
 	override fun clearContent() {
 		items.fill(ItemStack.EMPTY)
 		observedItems.fill(ItemStack.EMPTY)
+		bitmap.clear()
 	}
 
 	override fun setChanged() {
@@ -146,6 +204,7 @@ abstract class EnhancedContainer<out S : IContainerSlot>(private val size: Int)
 		val copy = observedItems.copyOf()
 		items.fill(ItemStack.EMPTY)
 		observedItems.fill(ItemStack.EMPTY)
+		bitmap.clear()
 
 		val seenSlots = IntOpenHashSet()
 		val ops = provider.createSerializationContext(NbtOps.INSTANCE)
@@ -166,6 +225,7 @@ abstract class EnhancedContainer<out S : IContainerSlot>(private val size: Int)
 							if (it.isNotEmpty) {
 								items[slot] = it
 								observedItems[slot] = it.copy()
+								bitmap[slot] = true
 
 								if (it.count != copy[slot].count || !ItemStack.isSameItemSameComponents(it, copy[slot]))
 									notifySlotChanged(slot, copy[slot])