From 633e77a34cf9741a48fd9b5f19e3c83d24fdb02b Mon Sep 17 00:00:00 2001
From: "Dylan K. Taylor" <dktapps@pmmp.io>
Date: Thu, 4 May 2023 23:21:54 +0100
Subject: [PATCH] RuntimeBlockMapping: share states CompoundTags if they are
 the same this allows saving about 4 MB of memory, because there are many
 blocks which have identical states, although they have different IDs.

this relies on a potentially risky assumption that the tags in knownStates won't be modified. If they are modified, the changes will influence all blockstates which share the tag.
However, I don't expect this to happen, and the 4 MB memory saving is substantial enough to be worth the risk.
---
 src/network/mcpe/convert/RuntimeBlockMapping.php | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/src/network/mcpe/convert/RuntimeBlockMapping.php b/src/network/mcpe/convert/RuntimeBlockMapping.php
index 64984c3c1..c2123364b 100644
--- a/src/network/mcpe/convert/RuntimeBlockMapping.php
+++ b/src/network/mcpe/convert/RuntimeBlockMapping.php
@@ -27,10 +27,12 @@ use pocketmine\block\Block;
 use pocketmine\block\BlockLegacyIds;
 use pocketmine\data\bedrock\BedrockDataFiles;
 use pocketmine\data\bedrock\LegacyBlockIdToStringIdMap;
+use pocketmine\nbt\LittleEndianNbtSerializer;
 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 pocketmine\utils\BinaryStream;
 use pocketmine\utils\Filesystem;
@@ -72,7 +74,7 @@ final class RuntimeBlockMapping{
 			$key = $keyIndex[$key] ??= $key;
 
 			if($value instanceof CompoundTag){
-				$value = self::deduplicateCompound($value, $keyIndex, $valueIndex);
+				$value = $valueIndex[$value->getType()][(new LittleEndianNbtSerializer())->write(new TreeRoot($value))] ??= self::deduplicateCompound($value, $keyIndex, $valueIndex);
 			}elseif($value instanceof ByteTag || $value instanceof IntTag || $value instanceof StringTag){
 				$value = $valueIndex[$value->getType()][$value->getValue()] ??= $value;
 			}