5 files changed, 216 insertions, 171 deletions

diff --git a/src/ChunkSender.cpp b/src/ChunkSender.cpp
index ec05258ae..e00b86795 100644
--- a/src/ChunkSender.cpp
+++ b/src/ChunkSender.cpp
@@ -11,7 +11,6 @@
 #include "ChunkSender.h"
 #include "World.h"
 #include "BlockEntities/BlockEntity.h"
-#include "Protocol/ChunkDataSerializer.h"
 #include "ClientHandle.h"
 #include "Chunk.h"
 
@@ -61,7 +60,8 @@ public:
 
 cChunkSender::cChunkSender(cWorld & a_World) :
 	Super("ChunkSender"),
-	m_World(a_World)
+	m_World(a_World),
+	m_Serializer(m_World.GetDimension())
 {
 }
 
@@ -246,11 +246,8 @@ void cChunkSender::SendChunk(int a_ChunkX, int a_ChunkZ, std::unordered_set<cCli
 		return;
 	}
 
-	{
-		// Send:
-		cChunkDataSerializer Data(a_ChunkX, a_ChunkZ, m_Data, m_BiomeMap, m_World.GetDimension());
-		Data.SendToClients(a_Clients);
-	}
+	// Send:
+	m_Serializer.SendToClients(a_ChunkX, a_ChunkZ, m_Data, m_BiomeMap, a_Clients);
 
 	for (const auto Client : a_Clients)
 	{
diff --git a/src/ChunkSender.h b/src/ChunkSender.h
index 7caf9424e..2d9c478e9 100644
--- a/src/ChunkSender.h
+++ b/src/ChunkSender.h
@@ -27,6 +27,7 @@ Note that it may be called by world's BroadcastToChunk() if the client is still
 
 #include "OSSupport/IsThread.h"
 #include "ChunkDataCallback.h"
+#include "Protocol/ChunkDataSerializer.h"
 
 
 
@@ -109,6 +110,9 @@ protected:
 
 	cWorld & m_World;
 
+	/** An instance of a chunk serializer, held to maintain its internal cache. */
+	cChunkDataSerializer m_Serializer;
+
 	cCriticalSection  m_CS;
 	std::priority_queue<sChunkQueue> m_SendChunks;
 	std::unordered_map<cChunkCoords, sSendChunk, cChunkCoordsHash> m_ChunkInfo;
diff --git a/src/ClientHandle.cpp b/src/ClientHandle.cpp
index c12e11f45..040c3a306 100644
--- a/src/ClientHandle.cpp
+++ b/src/ClientHandle.cpp
@@ -2479,7 +2479,8 @@ void cClientHandle::SendChunkData(int a_ChunkX, int a_ChunkZ, const std::string_
 	{
 		// This just sometimes happens. If you have a reliably replicatable situation for this, go ahead and fix it
 		// It's not a big issue anyway, just means that some chunks may be compressed several times
-		// LOGD("Refusing to send    chunk [%d, %d] to client \"%s\" at [%d, %d].", ChunkX, ChunkZ, m_Username.c_str(), m_Player->GetChunkX(), m_Player->GetChunkZ());
+		// LOG("Refusing to send    chunk [%d, %d] to client \"%s\" at [%d, %d].", a_ChunkX, a_ChunkZ, m_Username.c_str(), m_Player->GetChunkX(), m_Player->GetChunkZ());
+		// 2020 08 21: seems to happen going through nether portals on 1.8.9
 		return;
 	}
 
diff --git a/src/Protocol/ChunkDataSerializer.cpp b/src/Protocol/ChunkDataSerializer.cpp
index 680b9139b..2fd9e1cc2 100644
--- a/src/Protocol/ChunkDataSerializer.cpp
+++ b/src/Protocol/ChunkDataSerializer.cpp
@@ -3,7 +3,6 @@
 #include "zlib/zlib.h"
 #include "Protocol_1_8.h"
 #include "Protocol_1_9.h"
-#include "../ByteBuffer.h"
 #include "../ClientHandle.h"
 #include "../WorldStorage/FastNBT.h"
 
@@ -64,17 +63,8 @@ namespace
 ////////////////////////////////////////////////////////////////////////////////
 // cChunkDataSerializer:
 
-cChunkDataSerializer::cChunkDataSerializer(
-	int                   a_ChunkX,
-	int                   a_ChunkZ,
-	const cChunkData &    a_Data,
-	const unsigned char * a_BiomeData,
-	const eDimension      a_Dimension
-) :
-	m_ChunkX(a_ChunkX),
-	m_ChunkZ(a_ChunkZ),
-	m_Data(a_Data),
-	m_BiomeData(a_BiomeData),
+cChunkDataSerializer::cChunkDataSerializer(const eDimension a_Dimension) :
+	m_Packet(512 KiB),
 	m_Dimension(a_Dimension)
 {
 }
@@ -83,30 +73,22 @@ cChunkDataSerializer::cChunkDataSerializer(
 
 
 
-void cChunkDataSerializer::SendToClients(const std::unordered_set<cClientHandle *> & a_SendTo)
+void cChunkDataSerializer::SendToClients(const int a_ChunkX, const int a_ChunkZ, const cChunkData & a_Data, const unsigned char * a_BiomeData, const ClientHandles & a_SendTo)
 {
-	std::unordered_map<cProtocol::Version, std::vector<cClientHandle *>> ClientProtocolVersions;
-
 	for (const auto Client : a_SendTo)
 	{
-		const auto ClientProtocol = static_cast<cProtocol::Version>(Client->GetProtocolVersion());
-		ClientProtocolVersions[ClientProtocol].emplace_back(Client);
-	}
-
-	for (const auto & Entry : ClientProtocolVersions)
-	{
-		switch (Entry.first)
+		switch (static_cast<cProtocol::Version>(Client->GetProtocolVersion()))
 		{
 			case cProtocol::Version::v1_8_0:
 			{
-				Serialize47(Entry.second);
+				Serialize(Client, a_ChunkX, a_ChunkZ, a_Data, a_BiomeData, CacheVersion::v47);
 				continue;
 			}
 			case cProtocol::Version::v1_9_0:
 			case cProtocol::Version::v1_9_1:
 			case cProtocol::Version::v1_9_2:
 			{
-				Serialize107(Entry.second);
+				Serialize(Client, a_ChunkX, a_ChunkZ, a_Data, a_BiomeData, CacheVersion::v107);
 				continue;
 			}
 			case cProtocol::Version::v1_9_4:
@@ -117,106 +99,161 @@ void cChunkDataSerializer::SendToClients(const std::unordered_set<cClientHandle
 			case cProtocol::Version::v1_12_1:
 			case cProtocol::Version::v1_12_2:
 			{
-				Serialize110(Entry.second);
+				Serialize(Client, a_ChunkX, a_ChunkZ, a_Data, a_BiomeData, CacheVersion::v110);
 				continue;
 			}
 			case cProtocol::Version::v1_13:
 			{
-				Serialize393<&Palette393>(Entry.second);  // This version didn't last very long xD
+				Serialize(Client, a_ChunkX, a_ChunkZ, a_Data, a_BiomeData, CacheVersion::v393);  // This version didn't last very long xD
 				continue;
 			}
 			case cProtocol::Version::v1_13_1:
 			case cProtocol::Version::v1_13_2:
 			{
-				Serialize393<&Palette401>(Entry.second);
+				Serialize(Client, a_ChunkX, a_ChunkZ, a_Data, a_BiomeData, CacheVersion::v401);
 				continue;
 			}
 			case cProtocol::Version::v1_14:
 			{
-				Serialize477(Entry.second);
+				Serialize(Client, a_ChunkX, a_ChunkZ, a_Data, a_BiomeData, CacheVersion::v477);
 				continue;
 			}
 		}
 
 		UNREACHABLE("Unknown chunk data serialization version");
 	}
+
+	// Our cache is only persistent during the function call:
+	for (auto & Cache : m_Cache)
+	{
+		Cache.Engaged = false;
+	}
 }
 
 
 
 
 
-void cChunkDataSerializer::Serialize47(const std::vector<cClientHandle *> & a_SendTo)
+inline void cChunkDataSerializer::Serialize(cClientHandle * a_Client, const int a_ChunkX, const int a_ChunkZ, const cChunkData & a_Data, const unsigned char * a_BiomeData, const CacheVersion a_CacheVersion)
+{
+	auto & Cache = m_Cache[static_cast<size_t>(a_CacheVersion)];
+	if (Cache.Engaged)
+	{
+		// Success! We've done it already, just re-use:
+		a_Client->SendChunkData(a_ChunkX, a_ChunkZ, Cache.ToSend);
+		return;
+	}
+
+	switch (a_CacheVersion)
+	{
+		case CacheVersion::v47:
+		{
+			Serialize47(a_ChunkX, a_ChunkZ, a_Data, a_BiomeData);
+			break;
+		}
+		case CacheVersion::v107:
+		{
+			Serialize107(a_ChunkX, a_ChunkZ, a_Data, a_BiomeData);
+			break;
+		}
+		case CacheVersion::v110:
+		{
+			Serialize110(a_ChunkX, a_ChunkZ, a_Data, a_BiomeData);
+			break;
+		}
+		case CacheVersion::v393:
+		{
+			Serialize393<&Palette393>(a_ChunkX, a_ChunkZ, a_Data, a_BiomeData);
+			break;
+		}
+		case CacheVersion::v401:
+		{
+			Serialize393<&Palette401>(a_ChunkX, a_ChunkZ, a_Data, a_BiomeData);
+			break;
+		}
+		case CacheVersion::v477:
+		{
+			Serialize477(a_ChunkX, a_ChunkZ, a_Data, a_BiomeData);
+			break;
+		}
+	}
+
+	CompressPacketInto(Cache);
+	ASSERT(Cache.Engaged);  // Cache must be populated now
+	a_Client->SendChunkData(a_ChunkX, a_ChunkZ, Cache.ToSend);
+}
+
+
+
+
+
+inline void cChunkDataSerializer::Serialize47(const int a_ChunkX, const int a_ChunkZ, const cChunkData & a_Data, const unsigned char * a_BiomeData)
 {
 	// This function returns the fully compressed packet (including packet size), not the raw packet!
 
 	// Create the packet:
-	cByteBuffer Packet(512 KiB);
-	Packet.WriteVarInt32(0x21);  // Packet id (Chunk Data packet)
-	Packet.WriteBEInt32(m_ChunkX);
-	Packet.WriteBEInt32(m_ChunkZ);
-	Packet.WriteBool(true);      // "Ground-up continuous", or rather, "biome data present" flag
-	Packet.WriteBEUInt16(m_Data.GetSectionBitmask());
+	m_Packet.WriteVarInt32(0x21);  // Packet id (Chunk Data packet)
+	m_Packet.WriteBEInt32(a_ChunkX);
+	m_Packet.WriteBEInt32(a_ChunkZ);
+	m_Packet.WriteBool(true);      // "Ground-up continuous", or rather, "biome data present" flag
+	m_Packet.WriteBEUInt16(a_Data.GetSectionBitmask());
 
 	// Write the chunk size:
 	const int BiomeDataSize = cChunkDef::Width * cChunkDef::Width;
 	UInt32 ChunkSize = (
-		m_Data.NumPresentSections() * cChunkData::SectionBlockCount * 3 +  // Blocks and lighting
+		a_Data.NumPresentSections() * cChunkData::SectionBlockCount * 3 +  // Blocks and lighting
 		BiomeDataSize    // Biome data
 	);
-	Packet.WriteVarInt32(ChunkSize);
+	m_Packet.WriteVarInt32(ChunkSize);
 
 	// Chunk written as seperate arrays of (blocktype + meta), blocklight and skylight
 	// each array stores all present sections of the same kind packed together
 
 	// Write the block types to the packet:
-	ForEachSection(m_Data, [&](const cChunkData::sChunkSection & a_Section)
+	ForEachSection(a_Data, [&](const cChunkData::sChunkSection & a_Section)
 		{
 			for (size_t BlockIdx = 0; BlockIdx != cChunkData::SectionBlockCount; ++BlockIdx)
 			{
 				BLOCKTYPE BlockType = a_Section.m_BlockTypes[BlockIdx] & 0xFF;
 				NIBBLETYPE BlockMeta = a_Section.m_BlockMetas[BlockIdx / 2] >> ((BlockIdx & 1) * 4) & 0x0f;
-				Packet.WriteBEUInt8(static_cast<unsigned char>(BlockType << 4) | BlockMeta);
-				Packet.WriteBEUInt8(static_cast<unsigned char>(BlockType >> 4));
+				m_Packet.WriteBEUInt8(static_cast<unsigned char>(BlockType << 4) | BlockMeta);
+				m_Packet.WriteBEUInt8(static_cast<unsigned char>(BlockType >> 4));
 			}
 		}
 	);
 
 	// Write the block lights:
-	ForEachSection(m_Data, [&](const cChunkData::sChunkSection & a_Section)
+	ForEachSection(a_Data, [&](const cChunkData::sChunkSection & a_Section)
 		{
-			Packet.WriteBuf(a_Section.m_BlockLight, sizeof(a_Section.m_BlockLight));
+			m_Packet.WriteBuf(a_Section.m_BlockLight, sizeof(a_Section.m_BlockLight));
 		}
 	);
 
 	// Write the sky lights:
-	ForEachSection(m_Data, [&](const cChunkData::sChunkSection & a_Section)
+	ForEachSection(a_Data, [&](const cChunkData::sChunkSection & a_Section)
 		{
-			Packet.WriteBuf(a_Section.m_BlockSkyLight, sizeof(a_Section.m_BlockSkyLight));
+			m_Packet.WriteBuf(a_Section.m_BlockSkyLight, sizeof(a_Section.m_BlockSkyLight));
 		}
 	);
 
 	// Write the biome data:
-	Packet.WriteBuf(m_BiomeData, BiomeDataSize);
-
-	CompressAndSend(Packet, a_SendTo);
+	m_Packet.WriteBuf(a_BiomeData, BiomeDataSize);
 }
 
 
 
 
 
-void cChunkDataSerializer::Serialize107(const std::vector<cClientHandle *> & a_SendTo)
+inline void cChunkDataSerializer::Serialize107(const int a_ChunkX, const int a_ChunkZ, const cChunkData & a_Data, const unsigned char * a_BiomeData)
 {
 	// This function returns the fully compressed packet (including packet size), not the raw packet!
 
 	// Create the packet:
-	cByteBuffer Packet(512 KiB);
-	Packet.WriteVarInt32(0x20);  // Packet id (Chunk Data packet)
-	Packet.WriteBEInt32(m_ChunkX);
-	Packet.WriteBEInt32(m_ChunkZ);
-	Packet.WriteBool(true);        // "Ground-up continuous", or rather, "biome data present" flag
-	Packet.WriteVarInt32(m_Data.GetSectionBitmask());
+	m_Packet.WriteVarInt32(0x20);  // Packet id (Chunk Data packet)
+	m_Packet.WriteBEInt32(a_ChunkX);
+	m_Packet.WriteBEInt32(a_ChunkZ);
+	m_Packet.WriteBool(true);        // "Ground-up continuous", or rather, "biome data present" flag
+	m_Packet.WriteVarInt32(a_Data.GetSectionBitmask());
 	// Write the chunk size:
 	const UInt8 BitsPerEntry = 13;
 	const size_t ChunkSectionDataArraySize = (cChunkData::SectionBlockCount * BitsPerEntry) / 8 / 8;  // Convert from bit count to long count
@@ -236,50 +273,47 @@ void cChunkDataSerializer::Serialize107(const std::vector<cClientHandle *> & a_S
 
 	const size_t BiomeDataSize = cChunkDef::Width * cChunkDef::Width;
 	size_t ChunkSize = (
-		ChunkSectionSize * m_Data.NumPresentSections() +
+		ChunkSectionSize * a_Data.NumPresentSections() +
 		BiomeDataSize
 	);
-	Packet.WriteVarInt32(static_cast<UInt32>(ChunkSize));
+	m_Packet.WriteVarInt32(static_cast<UInt32>(ChunkSize));
 
 	// Write each chunk section...
-	ForEachSection(m_Data, [&](const cChunkData::sChunkSection & a_Section)
+	ForEachSection(a_Data, [&](const cChunkData::sChunkSection & a_Section)
 		{
-			Packet.WriteBEUInt8(BitsPerEntry);
-			Packet.WriteVarInt32(0);  // Palette length is 0
-			Packet.WriteVarInt32(static_cast<UInt32>(ChunkSectionDataArraySize));
-			WriteSectionDataSeamless<&PaletteLegacy>(Packet, a_Section, BitsPerEntry);
+			m_Packet.WriteBEUInt8(BitsPerEntry);
+			m_Packet.WriteVarInt32(0);  // Palette length is 0
+			m_Packet.WriteVarInt32(static_cast<UInt32>(ChunkSectionDataArraySize));
+			WriteSectionDataSeamless<&PaletteLegacy>(a_Section, BitsPerEntry);
 
 			// Write lighting:
-			Packet.WriteBuf(a_Section.m_BlockLight, sizeof(a_Section.m_BlockLight));
+			m_Packet.WriteBuf(a_Section.m_BlockLight, sizeof(a_Section.m_BlockLight));
 			if (m_Dimension == dimOverworld)
 			{
 				// Skylight is only sent in the overworld; the nether and end do not use it
-				Packet.WriteBuf(a_Section.m_BlockSkyLight, sizeof(a_Section.m_BlockSkyLight));
+				m_Packet.WriteBuf(a_Section.m_BlockSkyLight, sizeof(a_Section.m_BlockSkyLight));
 			}
 		}
 	);
 
 	// Write the biome data
-	Packet.WriteBuf(m_BiomeData, BiomeDataSize);
-
-	CompressAndSend(Packet, a_SendTo);
+	m_Packet.WriteBuf(a_BiomeData, BiomeDataSize);
 }
 
 
 
 
 
-void cChunkDataSerializer::Serialize110(const std::vector<cClientHandle *> & a_SendTo)
+inline void cChunkDataSerializer::Serialize110(const int a_ChunkX, const int a_ChunkZ, const cChunkData & a_Data, const unsigned char * a_BiomeData)
 {
 	// This function returns the fully compressed packet (including packet size), not the raw packet!
 
 	// Create the packet:
-	cByteBuffer Packet(512 KiB);
-	Packet.WriteVarInt32(0x20);  // Packet id (Chunk Data packet)
-	Packet.WriteBEInt32(m_ChunkX);
-	Packet.WriteBEInt32(m_ChunkZ);
-	Packet.WriteBool(true);        // "Ground-up continuous", or rather, "biome data present" flag
-	Packet.WriteVarInt32(m_Data.GetSectionBitmask());
+	m_Packet.WriteVarInt32(0x20);  // Packet id (Chunk Data packet)
+	m_Packet.WriteBEInt32(a_ChunkX);
+	m_Packet.WriteBEInt32(a_ChunkZ);
+	m_Packet.WriteBool(true);        // "Ground-up continuous", or rather, "biome data present" flag
+	m_Packet.WriteVarInt32(a_Data.GetSectionBitmask());
 	// Write the chunk size:
 	const UInt8 BitsPerEntry = 13;
 	const size_t ChunkSectionDataArraySize = (cChunkData::SectionBlockCount * BitsPerEntry) / 8 / 8;  // Convert from bit count to long count
@@ -299,36 +333,34 @@ void cChunkDataSerializer::Serialize110(const std::vector<cClientHandle *> & a_S
 
 	const size_t BiomeDataSize = cChunkDef::Width * cChunkDef::Width;
 	size_t ChunkSize = (
-		ChunkSectionSize * m_Data.NumPresentSections() +
+		ChunkSectionSize * a_Data.NumPresentSections() +
 		BiomeDataSize
 	);
-	Packet.WriteVarInt32(static_cast<UInt32>(ChunkSize));
+	m_Packet.WriteVarInt32(static_cast<UInt32>(ChunkSize));
 
 	// Write each chunk section...
-	ForEachSection(m_Data, [&](const cChunkData::sChunkSection & a_Section)
+	ForEachSection(a_Data, [&](const cChunkData::sChunkSection & a_Section)
 		{
-			Packet.WriteBEUInt8(BitsPerEntry);
-			Packet.WriteVarInt32(0);  // Palette length is 0
-			Packet.WriteVarInt32(static_cast<UInt32>(ChunkSectionDataArraySize));
-			WriteSectionDataSeamless<&PaletteLegacy>(Packet, a_Section, BitsPerEntry);
+			m_Packet.WriteBEUInt8(BitsPerEntry);
+			m_Packet.WriteVarInt32(0);  // Palette length is 0
+			m_Packet.WriteVarInt32(static_cast<UInt32>(ChunkSectionDataArraySize));
+			WriteSectionDataSeamless<&PaletteLegacy>(a_Section, BitsPerEntry);
 
 			// Write lighting:
-			Packet.WriteBuf(a_Section.m_BlockLight, sizeof(a_Section.m_BlockLight));
+			m_Packet.WriteBuf(a_Section.m_BlockLight, sizeof(a_Section.m_BlockLight));
 			if (m_Dimension == dimOverworld)
 			{
 				// Skylight is only sent in the overworld; the nether and end do not use it
-				Packet.WriteBuf(a_Section.m_BlockSkyLight, sizeof(a_Section.m_BlockSkyLight));
+				m_Packet.WriteBuf(a_Section.m_BlockSkyLight, sizeof(a_Section.m_BlockSkyLight));
 			}
 		}
 	);
 
 	// Write the biome data
-	Packet.WriteBuf(m_BiomeData, BiomeDataSize);
+	m_Packet.WriteBuf(a_BiomeData, BiomeDataSize);
 
 	// Identify 1.9.4's tile entity list as empty
-	Packet.WriteBEUInt8(0);
-
-	CompressAndSend(Packet, a_SendTo);
+	m_Packet.WriteBEUInt8(0);
 }
 
 
@@ -336,24 +368,23 @@ void cChunkDataSerializer::Serialize110(const std::vector<cClientHandle *> & a_S
 
 
 template <auto Palette>
-void cChunkDataSerializer::Serialize393(const std::vector<cClientHandle *> & a_SendTo)
+inline void cChunkDataSerializer::Serialize393(const int a_ChunkX, const int a_ChunkZ, const cChunkData & a_Data, const unsigned char * a_BiomeData)
 {
 	// This function returns the fully compressed packet (including packet size), not the raw packet!
 
 	// Create the packet:
-	cByteBuffer Packet(512 KiB);
-	Packet.WriteVarInt32(0x22);  // Packet id (Chunk Data packet)
-	Packet.WriteBEInt32(m_ChunkX);
-	Packet.WriteBEInt32(m_ChunkZ);
-	Packet.WriteBool(true);  // "Ground-up continuous", or rather, "biome data present" flag
-	Packet.WriteVarInt32(m_Data.GetSectionBitmask());
+	m_Packet.WriteVarInt32(0x22);  // Packet id (Chunk Data packet)
+	m_Packet.WriteBEInt32(a_ChunkX);
+	m_Packet.WriteBEInt32(a_ChunkZ);
+	m_Packet.WriteBool(true);  // "Ground-up continuous", or rather, "biome data present" flag
+	m_Packet.WriteVarInt32(a_Data.GetSectionBitmask());
 
 	// Write the chunk size in bytes:
 	const UInt8 BitsPerEntry = 14;
 	const size_t ChunkSectionDataArraySize = (cChunkData::SectionBlockCount * BitsPerEntry) / 8 / 8;
 	size_t ChunkSectionSize = (
 		1 +  // Bits per entry, BEUInt8, 1 byte
-		Packet.GetVarIntSize(static_cast<UInt32>(ChunkSectionDataArraySize)) +  // Field containing "size of whole section", VarInt32, variable size
+		m_Packet.GetVarIntSize(static_cast<UInt32>(ChunkSectionDataArraySize)) +  // Field containing "size of whole section", VarInt32, variable size
 		ChunkSectionDataArraySize * 8 +  // Actual section data, lots of bytes (multiplier 1 long = 8 bytes)
 		cChunkData::SectionBlockCount / 2  // Size of blocklight which is always sent
 	);
@@ -366,24 +397,24 @@ void cChunkDataSerializer::Serialize393(const std::vector<cClientHandle *> & a_S
 
 	const size_t BiomeDataSize = cChunkDef::Width * cChunkDef::Width;
 	size_t ChunkSize = (
-		ChunkSectionSize * m_Data.NumPresentSections() +
+		ChunkSectionSize * a_Data.NumPresentSections() +
 		BiomeDataSize * 4  // Biome data now BE ints
 	);
-	Packet.WriteVarInt32(static_cast<UInt32>(ChunkSize));
+	m_Packet.WriteVarInt32(static_cast<UInt32>(ChunkSize));
 
 	// Write each chunk section...
-	ForEachSection(m_Data, [&](const cChunkData::sChunkSection & a_Section)
+	ForEachSection(a_Data, [&](const cChunkData::sChunkSection & a_Section)
 		{
-			Packet.WriteBEUInt8(BitsPerEntry);
-			Packet.WriteVarInt32(static_cast<UInt32>(ChunkSectionDataArraySize));
-			WriteSectionDataSeamless<Palette>(Packet, a_Section, BitsPerEntry);
+			m_Packet.WriteBEUInt8(BitsPerEntry);
+			m_Packet.WriteVarInt32(static_cast<UInt32>(ChunkSectionDataArraySize));
+			WriteSectionDataSeamless<Palette>(a_Section, BitsPerEntry);
 
 			// Write lighting:
-			Packet.WriteBuf(a_Section.m_BlockLight, sizeof(a_Section.m_BlockLight));
+			m_Packet.WriteBuf(a_Section.m_BlockLight, sizeof(a_Section.m_BlockLight));
 			if (m_Dimension == dimOverworld)
 			{
 				// Skylight is only sent in the overworld; the nether and end do not use it
-				Packet.WriteBuf(a_Section.m_BlockSkyLight, sizeof(a_Section.m_BlockSkyLight));
+				m_Packet.WriteBuf(a_Section.m_BlockSkyLight, sizeof(a_Section.m_BlockSkyLight));
 			}
 		}
 	);
@@ -391,30 +422,27 @@ void cChunkDataSerializer::Serialize393(const std::vector<cClientHandle *> & a_S
 	// Write the biome data
 	for (size_t i = 0; i != BiomeDataSize; i++)
 	{
-		Packet.WriteBEUInt32(static_cast<UInt32>(m_BiomeData[i]) & 0xff);
+		m_Packet.WriteBEUInt32(static_cast<UInt32>(a_BiomeData[i]) & 0xff);
 	}
 
 	// Identify 1.9.4's tile entity list as empty
-	Packet.WriteVarInt32(0);
-
-	CompressAndSend(Packet, a_SendTo);
+	m_Packet.WriteVarInt32(0);
 }
 
 
 
 
 
-void cChunkDataSerializer::Serialize477(const std::vector<cClientHandle *> & a_SendTo)
+inline void cChunkDataSerializer::Serialize477(const int a_ChunkX, const int a_ChunkZ, const cChunkData & a_Data, const unsigned char * a_BiomeData)
 {
 	// This function returns the fully compressed packet (including packet size), not the raw packet!
 
 	// Create the packet:
-	cByteBuffer Packet(512 KiB);
-	Packet.WriteVarInt32(0x21);  // Packet id (Chunk Data packet)
-	Packet.WriteBEInt32(m_ChunkX);
-	Packet.WriteBEInt32(m_ChunkZ);
-	Packet.WriteBool(true);  // "Ground-up continuous", or rather, "biome data present" flag
-	Packet.WriteVarInt32(m_Data.GetSectionBitmask());
+	m_Packet.WriteVarInt32(0x21);  // Packet id (Chunk Data packet)
+	m_Packet.WriteBEInt32(a_ChunkX);
+	m_Packet.WriteBEInt32(a_ChunkZ);
+	m_Packet.WriteBool(true);  // "Ground-up continuous", or rather, "biome data present" flag
+	m_Packet.WriteVarInt32(a_Data.GetSectionBitmask());
 
 	{
 		cFastNBTWriter Writer;
@@ -422,7 +450,7 @@ void cChunkDataSerializer::Serialize477(const std::vector<cClientHandle *> & a_S
 		// std::array<Int64, 36> Longz = {};
 		// Writer.AddLongArray("MOTION_BLOCKING", Longz.data(), Longz.size());
 		Writer.Finish();
-		Packet.Write(Writer.GetResult().data(), Writer.GetResult().size());
+		m_Packet.Write(Writer.GetResult().data(), Writer.GetResult().size());
 	}
 
 	// Write the chunk size in bytes:
@@ -431,37 +459,35 @@ void cChunkDataSerializer::Serialize477(const std::vector<cClientHandle *> & a_S
 	const size_t ChunkSectionSize = (
 		2 +  // Block count, BEInt16, 2 bytes
 		1 +  // Bits per entry, BEUInt8, 1 byte
-		Packet.GetVarIntSize(static_cast<UInt32>(ChunkSectionDataArraySize)) +  // Field containing "size of whole section", VarInt32, variable size
+		m_Packet.GetVarIntSize(static_cast<UInt32>(ChunkSectionDataArraySize)) +  // Field containing "size of whole section", VarInt32, variable size
 		ChunkSectionDataArraySize * 8  // Actual section data, lots of bytes (multiplier 1 long = 8 bytes)
 	);
 
 	const size_t BiomeDataSize = cChunkDef::Width * cChunkDef::Width;
 	const size_t ChunkSize = (
-		ChunkSectionSize * m_Data.NumPresentSections() +
+		ChunkSectionSize * a_Data.NumPresentSections() +
 		BiomeDataSize * 4  // Biome data now BE ints
 	);
-	Packet.WriteVarInt32(static_cast<UInt32>(ChunkSize));
+	m_Packet.WriteVarInt32(static_cast<UInt32>(ChunkSize));
 
 	// Write each chunk section...
-	ForEachSection(m_Data, [&](const cChunkData::sChunkSection & a_Section)
+	ForEachSection(a_Data, [&](const cChunkData::sChunkSection & a_Section)
 		{
-			Packet.WriteBEInt16(-1);
-			Packet.WriteBEUInt8(BitsPerEntry);
-			Packet.WriteVarInt32(static_cast<UInt32>(ChunkSectionDataArraySize));
-			WriteSectionDataSeamless<&Palette477>(Packet, a_Section, BitsPerEntry);
+			m_Packet.WriteBEInt16(-1);
+			m_Packet.WriteBEUInt8(BitsPerEntry);
+			m_Packet.WriteVarInt32(static_cast<UInt32>(ChunkSectionDataArraySize));
+			WriteSectionDataSeamless<&Palette477>(a_Section, BitsPerEntry);
 		}
 	);
 
 	// Write the biome data
 	for (size_t i = 0; i != BiomeDataSize; i++)
 	{
-		Packet.WriteBEUInt32(static_cast<UInt32>(m_BiomeData[i]) & 0xff);
+		m_Packet.WriteBEUInt32(static_cast<UInt32>(a_BiomeData[i]) & 0xff);
 	}
 
 	// Identify 1.9.4's tile entity list as empty
-	Packet.WriteVarInt32(0);
-
-	CompressAndSend(Packet, a_SendTo);
+	m_Packet.WriteVarInt32(0);
 }
 
 
@@ -469,7 +495,7 @@ void cChunkDataSerializer::Serialize477(const std::vector<cClientHandle *> & a_S
 
 
 template <auto Palette>
-void cChunkDataSerializer::WriteSectionDataSeamless(cByteBuffer & a_Packet, const cChunkData::sChunkSection & a_Section, const UInt8 a_BitsPerEntry)
+inline void cChunkDataSerializer::WriteSectionDataSeamless(const cChunkData::sChunkSection & a_Section, const UInt8 a_BitsPerEntry)
 {
 	// https://wiki.vg/Chunk_Format#Data_structure
 
@@ -493,7 +519,7 @@ void cChunkDataSerializer::WriteSectionDataSeamless(cByteBuffer & a_Packet, cons
 		if (Remaining >= 0)
 		{
 			// There were some bits remaining: we've filled the buffer. Flush it:
-			a_Packet.WriteBEUInt64(Buffer);
+			m_Packet.WriteBEUInt64(Buffer);
 
 			// And write the remaining bits, setting the new BitIndex:
 			Buffer = Value >> (a_BitsPerEntry - Remaining);
@@ -515,20 +541,16 @@ void cChunkDataSerializer::WriteSectionDataSeamless(cByteBuffer & a_Packet, cons
 
 
 
-void cChunkDataSerializer::CompressAndSend(cByteBuffer & a_Packet, const std::vector<cClientHandle *> & a_SendTo)
+inline void cChunkDataSerializer::CompressPacketInto(ChunkDataCache & a_Cache)
 {
-	AString PacketData;
-	a_Packet.ReadAll(PacketData);
+	m_Packet.ReadAll(a_Cache.PacketData);
+	m_Packet.CommitRead();
 
-	AString ToSend;
-	if (!cProtocol_1_8_0::CompressPacket(PacketData, ToSend))
+	if (!cProtocol_1_8_0::CompressPacket(a_Cache.PacketData, a_Cache.ToSend))
 	{
 		ASSERT(!"Packet compression failed.");
 		return;
 	}
 
-	for (const auto Client : a_SendTo)
-	{
-		Client->SendChunkData(m_ChunkX, m_ChunkZ, ToSend);
-	}
+	a_Cache.Engaged = true;
 }
diff --git a/src/Protocol/ChunkDataSerializer.h b/src/Protocol/ChunkDataSerializer.h
index f02bdd4d0..cb39e27d6 100644
--- a/src/Protocol/ChunkDataSerializer.h
+++ b/src/Protocol/ChunkDataSerializer.h
@@ -1,5 +1,6 @@
 #pragma once
 
+#include "../ByteBuffer.h"
 #include "../ChunkData.h"
 #include "../Defines.h"
 
@@ -18,47 +19,67 @@ Caches the serialized data for as long as this object lives, so that the same da
 other clients using the same protocol. */
 class cChunkDataSerializer
 {
+	using ClientHandles = std::unordered_set<cClientHandle *>;
+
+	/** Enum to collapse protocol versions into a contiguous index. */
+	enum class CacheVersion
+	{
+		v47,
+		v107,
+		v110,
+		v393,
+		v401,
+		v477,
+
+		Count
+	};
+
+	/** A single cache entry containing the raw data, compressed data, and a validity flag. */
+	struct ChunkDataCache
+	{
+		std::string PacketData;
+		std::string ToSend;
+		bool Engaged = false;
+	};
+
 public:
 
-	cChunkDataSerializer(
-		int                                         a_ChunkX,
-		int                                         a_ChunkZ,
-		const cChunkData &                          a_Data,
-		const unsigned char *                       a_BiomeData,
-		const eDimension                            a_Dimension
-	);
+	cChunkDataSerializer(eDimension a_Dimension);
 
-	/** For each client, serializes the chunk into their protocol version and sends it. */
-	void SendToClients(const std::unordered_set<cClientHandle *> & a_SendTo);
+	/** For each client, serializes the chunk into their protocol version and sends it.
+	Parameters are the coordinates of the chunk to serialise, and the data and biome data read from the chunk. */
+	void SendToClients(int a_ChunkX, int a_ChunkZ, const cChunkData & a_Data, const unsigned char * a_BiomeData, const ClientHandles & a_SendTo);
 
 protected:
 
-	void Serialize47 (const std::vector<cClientHandle *> & a_SendTo);  // Release 1.8
-	void Serialize107(const std::vector<cClientHandle *> & a_SendTo);  // Release 1.9
-	void Serialize110(const std::vector<cClientHandle *> & a_SendTo);  // Release 1.9.4
+	/** Serialises the given chunk, storing the result into the given cache entry, and sends the data.
+	If the cache entry is already present, simply re-uses it. */
+	inline void Serialize(cClientHandle * a_Client, int a_ChunkX, int a_ChunkZ, const cChunkData & a_Data, const unsigned char * a_BiomeData, CacheVersion a_CacheVersion);
+
+	inline void Serialize47 (int a_ChunkX, int a_ChunkZ, const cChunkData & a_Data, const unsigned char * a_BiomeData);  // Release 1.8
+	inline void Serialize107(int a_ChunkX, int a_ChunkZ, const cChunkData & a_Data, const unsigned char * a_BiomeData);  // Release 1.9
+	inline void Serialize110(int a_ChunkX, int a_ChunkZ, const cChunkData & a_Data, const unsigned char * a_BiomeData);  // Release 1.9.4
 	template <auto Palette>
-	void Serialize393(const std::vector<cClientHandle *> & a_SendTo);  // Release 1.13 - 1.13.2
-	void Serialize477(const std::vector<cClientHandle *> & a_SendTo);  // Release 1.14 - 1.14.4
+	inline void Serialize393(int a_ChunkX, int a_ChunkZ, const cChunkData & a_Data, const unsigned char * a_BiomeData);  // Release 1.13 - 1.13.2
+	inline void Serialize477(int a_ChunkX, int a_ChunkZ, const cChunkData & a_Data, const unsigned char * a_BiomeData);  // Release 1.14 - 1.14.4
 
 	/** Writes all blocks in a chunk section into a series of Int64.
 	Writes start from the bit directly subsequent to the previous write's end, possibly crossing over to the next Int64. */
 	template <auto Palette>
-	inline void WriteSectionDataSeamless(cByteBuffer & a_Packet, const cChunkData::sChunkSection & a_Section, const UInt8 a_BitsPerEntry);
-
-	/** Finalises the data, compresses it if required, and delivers it to all clients. */
-	void CompressAndSend(cByteBuffer & a_Packet, const std::vector<cClientHandle *> & a_SendTo);
+	inline void WriteSectionDataSeamless(const cChunkData::sChunkSection & a_Section, const UInt8 a_BitsPerEntry);
 
-	/** The coordinates of the chunk to serialise. */
-	int m_ChunkX, m_ChunkZ;
+	/** Finalises the data, compresses it if required, and stores it into cache. */
+	inline void CompressPacketInto(ChunkDataCache & a_Cache);
 
-	/** The data read from the chunk, to be serialized. */
-	const cChunkData & m_Data;
+	/** A staging area used to construct the chunk packet, persistent to avoid reallocating. */
+	cByteBuffer m_Packet;
 
-	/** The biomes in the chunk, to be serialized. */
-	const unsigned char * m_BiomeData;
-
-	/** The dimension where the chunk resides. */
+	/** The dimension for the World this Serializer is tied to. */
 	const eDimension m_Dimension;
+
+	/** A cache, mapping protocol version to a fully serialised chunk.
+	It is used during a single invocation of SendToClients with more than one client. */
+	std::array<ChunkDataCache, static_cast<size_t>(CacheVersion::Count)> m_Cache;
 } ;