BlockStateDictionary: reduce memory footprint by 5 MB by deduplicating blockstate NBT keys and values

src/network/mcpe/convert/BlockStateDictionary.php

@@ -25,6 +25,10 @@ namespace pocketmine\network\mcpe\convert;
 
 use pocketmine\data\bedrock\block\BlockStateData;
 use pocketmine\nbt\NbtDataException;
+use pocketmine\nbt\tag\ByteTag;
+use pocketmine\nbt\tag\CompoundTag;
+use pocketmine\nbt\tag\IntTag;
+use pocketmine\nbt\tag\StringTag;
 use pocketmine\nbt\TreeRoot;
 use pocketmine\network\mcpe\protocol\serializer\NetworkNbtSerializer;
 use function array_map;
@@ -108,6 +112,33 @@ final class BlockStateDictionary{
 	 */
 	public function getStates() : array{ return $this->states; }
 
+	/**
+	 * @param string[] $keyIndex
+	 * @param (ByteTag|StringTag|IntTag)[][] $valueIndex
+	 * @phpstan-param array<string, string> $keyIndex
+	 * @phpstan-param array<int, array<int|string, ByteTag|IntTag|StringTag>> $valueIndex
+	 */
+	private static function deduplicateCompound(CompoundTag $tag, array &$keyIndex, array &$valueIndex) : CompoundTag{
+		if($tag->count() === 0){
+			return $tag;
+		}
+
+		$newTag = CompoundTag::create();
+		foreach($tag as $key => $value){
+			$key = $keyIndex[$key] ??= $key;
+
+			if($value instanceof CompoundTag){
+				$value = self::deduplicateCompound($value, $keyIndex, $valueIndex);
+			}elseif($value instanceof ByteTag || $value instanceof IntTag || $value instanceof StringTag){
+				$value = $valueIndex[$value->getType()][$value->getValue()] ??= $value;
+			}
+
+			$newTag->setTag($key, $value);
+		}
+
+		return $newTag;
+	}
+
 	/**
 	 * @return BlockStateData[]
 	 * @phpstan-return list<BlockStateData>
@@ -115,8 +146,13 @@ final class BlockStateDictionary{
 	 * @throws NbtDataException
 	 */
 	public static function loadPaletteFromString(string $blockPaletteContents) : array{
+		$keyIndex = [];
+		$valueIndex = [];
+
 		return array_map(
-			fn(TreeRoot $root) => BlockStateData::fromNbt($root->mustGetCompoundTag()),
+			function(TreeRoot $root) use (&$keyIndex, &$valueIndex) : BlockStateData{
+				return BlockStateData::fromNbt(self::deduplicateCompound($root->mustGetCompoundTag(), $keyIndex, $valueIndex));
+			},
 			(new NetworkNbtSerializer())->readMultiple($blockPaletteContents)
 		);
 	}