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Refactor & optimize 1.8 chunk reading/writing #1567

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66fcc5f
Refactor & optimize 1.8 chunk reading/writing
Beaness Aug 7, 2026
25780b1
Rename parameters to be a bit more clear
Beaness Aug 8, 2026
56368d6
Always create a blocklight array if needed
Beaness Aug 8, 2026
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4 changes: 4 additions & 0 deletions ...ain/java/com/github/retrooper/packetevents/protocol/world/chunk/impl/v1_8/Chunk_v1_8.java
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Original file line number Diff line number Diff line change
Expand Up @@ -44,6 +44,10 @@ public ShortArray3d getBlocks() {
}

public NibbleArray3d getBlockLight() {
// Create block light array if needed, as block light is not optional in 1.8.9
if (this.blocklight == null) {
this.blocklight = new NibbleArray3d(4096);
}
return this.blocklight;
}

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269 changes: 172 additions & 97 deletions .../com/github/retrooper/packetevents/protocol/world/chunk/reader/impl/ChunkReader_v1_8.java
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Original file line number Diff line number Diff line change
Expand Up @@ -22,11 +22,11 @@
import com.github.retrooper.packetevents.protocol.world.chunk.BaseChunk;
import com.github.retrooper.packetevents.protocol.world.chunk.NetworkChunkData;
import com.github.retrooper.packetevents.protocol.world.chunk.NibbleArray3d;
import com.github.retrooper.packetevents.protocol.world.chunk.ShortArray3d;
import com.github.retrooper.packetevents.protocol.world.chunk.impl.v1_8.Chunk_v1_8;
import com.github.retrooper.packetevents.protocol.world.chunk.reader.ChunkReader;
import com.github.retrooper.packetevents.protocol.world.dimension.DimensionType;
import com.github.retrooper.packetevents.wrapper.PacketWrapper;
import org.jetbrains.annotations.ApiStatus;

import java.nio.ByteBuffer;
import java.nio.ByteOrder;
Expand All @@ -35,128 +35,203 @@

public class ChunkReader_v1_8 implements ChunkReader {

private static final int SECTION_COUNT = 16;
private static final int BLOCK_COUNT = 4096;
private static final int BLOCK_DATA_LENGTH = BLOCK_COUNT * Short.BYTES;
private static final int LIGHT_DATA_LENGTH = BLOCK_COUNT / 2;
private static final int BIOME_DATA_LENGTH = 16 * 16;

@Override
public BaseChunk[] read(
DimensionType dimensionType, BitSet chunkMask, BitSet secondaryChunkMask, boolean fullChunk,
boolean hasBlockLight, boolean hasSkyLight, int chunkSize, int arrayLength, PacketWrapper<?> wrapper
boolean forceSkyLight, boolean checkForSkyLight, int chunkSize, int arrayLength, PacketWrapper<?> wrapper
) {
byte[] data = wrapper.readByteArrayOfSize(arrayLength);
int populatedSections = 0;
for (int index = 0; index < SECTION_COUNT; index++) {
if (chunkMask.get(index)) {
populatedSections++;
}
}

Chunk_v1_8[] chunks = new Chunk_v1_8[16];
int pos = 0;
int expected = fullChunk ? 256 : 0; // 256 if full chunk for the biome data, always sent if full chunk
boolean sky = false;

ShortBuffer buf = ByteBuffer.wrap(data).order(ByteOrder.LITTLE_ENDIAN).asShortBuffer();

// 0 = Calculate expected length and determine if the packet has skylight.
// 1 = Create chunks from mask and get blocks.
// 2 = Get block light.
// 3 = Get sky light.
for (int pass = 0; pass < 4; pass++) {
for (int ind = 0; ind < 16; ind++) {
if (chunkMask.get(ind)) {
if (pass == 0) {
// Block length + Blocklight length
expected += (4096 * 2) + 2048;
}

if (pass == 1) {
chunks[ind] = new Chunk_v1_8(sky || hasBlockLight);
ShortArray3d blocks = chunks[ind].getBlocks();
buf.position(pos / 2);
buf.get(blocks.getData(), 0, blocks.getData().length);
pos += blocks.getData().length * 2;
}

if (pass == 2) {
NibbleArray3d blocklight = chunks[ind].getBlockLight();
System.arraycopy(data, pos, blocklight.getData(), 0, blocklight.getData().length);
pos += blocklight.getData().length;
}

if (pass == 3 && (sky || hasBlockLight)) {
NibbleArray3d skylight = chunks[ind].getSkyLight();
System.arraycopy(data, pos, skylight.getData(), 0, skylight.getData().length);
pos += skylight.getData().length;
}
}
int sectionDataLength = populatedSections * (BLOCK_DATA_LENGTH + LIGHT_DATA_LENGTH);
int expectedWithoutSkyLight = sectionDataLength + (fullChunk ? BIOME_DATA_LENGTH : 0);
// Bulk packets specify skylight; regular packets infer it from the payload length.
boolean skyLight = forceSkyLight || arrayLength > expectedWithoutSkyLight && checkForSkyLight;
int requiredSectionDataLength = sectionDataLength
+ (skyLight ? populatedSections * LIGHT_DATA_LENGTH : 0);
if (arrayLength < requiredSectionDataLength) {
throw new IllegalArgumentException("1.8 chunk data is shorter than its section mask requires ("
+ arrayLength + " < " + requiredSectionDataLength + ")");
}

Chunk_v1_8[] chunks = new Chunk_v1_8[SECTION_COUNT];
// Reuse one buffer for little-endian block data.
byte[] encodedBlocks = populatedSections == 0 ? null : new byte[BLOCK_DATA_LENGTH];
ShortBuffer decodedBlocks = encodedBlocks == null ? null
: ByteBuffer.wrap(encodedBlocks).order(ByteOrder.LITTLE_ENDIAN).asShortBuffer();

for (int index = 0; index < SECTION_COUNT; index++) {
if (chunkMask.get(index)) {
Chunk_v1_8 chunk = new Chunk_v1_8(skyLight);
chunks[index] = chunk;
ByteBufHelper.readBytes(wrapper.buffer, encodedBlocks);
short[] blocks = chunk.getBlocks().getData();
decodedBlocks.position(0);
decodedBlocks.get(blocks, 0, blocks.length);
}
}

if (pass == 0 && data.length > expected) {
// If we have more data than blocks and blocklight combined, there must be skylight data as well.
sky = hasSkyLight;
for (int index = 0; index < SECTION_COUNT; index++) {
Chunk_v1_8 chunk = chunks[index];
if (chunk != null) {
ByteBufHelper.readBytes(wrapper.buffer, chunk.getBlockLight().getData());
}
}

// reset reader index of buffer to end of data, we still need to read biome data
int ri = ByteBufHelper.readerIndex(wrapper.buffer);
ByteBufHelper.readerIndex(wrapper.buffer, ri - (arrayLength - pos));
if (skyLight) {
for (int index = 0; index < SECTION_COUNT; index++) {
Chunk_v1_8 chunk = chunks[index];
if (chunk != null) {
ByteBufHelper.readBytes(wrapper.buffer, chunk.getSkyLight().getData());
}
}
}

return chunks;
}

@Deprecated
public static NetworkChunkData chunksToData(Chunk_v1_8[] chunks, byte[] biomes) {
int chunkMask = 0;
boolean fullChunk = biomes != null;
boolean sky = false;
int length = fullChunk ? biomes.length : 0;
byte[] data = null;
int chunkMask = calculateChunkMask(chunks, fullChunk);
boolean sky = hasSkyLight(chunks, chunkMask);
byte[] data = new byte[calculateDataLength(chunks, biomes, chunkMask)];
int pos = 0;
ShortBuffer buf = null;

// 0 = Determine length and masks.
// 1 = Add blocks.
// 2 = Add block light.
// 3 = Add sky light.
for (int pass = 0; pass < 4; pass++) {
for (int ind = 0; ind < chunks.length; ++ind) {
Chunk_v1_8 chunk = chunks[ind];
if (chunk != null && (!fullChunk || !chunk.isEmpty())) {
if (pass == 0) {
chunkMask |= 1 << ind;
length += chunk.getBlocks().getData().length * 2;
length += chunk.getBlockLight().getData().length;
if (chunk.getSkyLight() != null) {
length += chunk.getSkyLight().getData().length;
}
}

if (pass == 1) {
short blocks[] = chunk.getBlocks().getData();
buf.position(pos / 2);
buf.put(blocks, 0, blocks.length);
pos += blocks.length * 2;
}

if (pass == 2) {
byte blocklight[] = chunk.getBlockLight().getData();
System.arraycopy(blocklight, 0, data, pos, blocklight.length);
pos += blocklight.length;
}

if (pass == 3 && chunk.getSkyLight() != null) {
byte skylight[] = chunk.getSkyLight().getData();
System.arraycopy(skylight, 0, data, pos, skylight.length);
pos += skylight.length;
sky = true;
}
}
ShortBuffer blockData = ByteBuffer.wrap(data).order(ByteOrder.LITTLE_ENDIAN).asShortBuffer();

for (int index = 0; index < chunks.length; index++) {
if ((chunkMask & 1 << index) != 0) {
short[] blocks = chunks[index].getBlocks().getData();
blockData.position(pos / Short.BYTES);
blockData.put(blocks, 0, blocks.length);
pos += blocks.length * Short.BYTES;
}
}

if (pass == 0) {
data = new byte[length];
buf = ByteBuffer.wrap(data).order(ByteOrder.LITTLE_ENDIAN).asShortBuffer();
for (int index = 0; index < chunks.length; index++) {
if ((chunkMask & 1 << index) != 0) {
byte[] blockLight = chunks[index].getBlockLight().getData();
System.arraycopy(blockLight, 0, data, pos, blockLight.length);
pos += blockLight.length;
}
}

for (int index = 0; index < chunks.length; index++) {
if ((chunkMask & 1 << index) != 0) {
NibbleArray3d skyLight = chunks[index].getSkyLight();
if (skyLight != null) {
byte[] skyLightData = skyLight.getData();
System.arraycopy(skyLightData, 0, data, pos, skyLightData.length);
pos += skyLightData.length;
}
}
}

// Add biomes.
if (fullChunk) {
System.arraycopy(biomes, 0, data, pos, biomes.length);
pos += biomes.length;
}

return new NetworkChunkData(chunkMask, fullChunk, sky, data);
}
}

@ApiStatus.Internal
public static int calculateChunkMask(Chunk_v1_8[] chunks, boolean fullChunk) {
int chunkMask = 0;
for (int index = 0; index < chunks.length; index++) {
Chunk_v1_8 chunk = chunks[index];
if (chunk != null && (!fullChunk || !chunk.isEmpty())) {
chunkMask |= 1 << index;
}
}
return chunkMask;
}

@ApiStatus.Internal
public static int calculateDataLength(Chunk_v1_8[] chunks, byte[] biomes, int chunkMask) {
int length = biomes == null ? 0 : biomes.length;
for (int index = 0; index < chunks.length; index++) {
if ((chunkMask & 1 << index) != 0) {
Chunk_v1_8 chunk = chunks[index];
length += chunk.getBlocks().getData().length * Short.BYTES;
length += chunk.getBlockLight().getData().length;
if (chunk.getSkyLight() != null) {
length += chunk.getSkyLight().getData().length;
}
}
}
return length;
}

@ApiStatus.Internal
public static boolean hasSkyLight(Chunk_v1_8[] chunks, int chunkMask) {
for (int index = 0; index < chunks.length; index++) {
if ((chunkMask & 1 << index) != 0 && chunks[index].getSkyLight() != null) {
return true;
}
}
return false;
}

@ApiStatus.Internal
public static void writeChunkData(
PacketWrapper<?> wrapper, Chunk_v1_8[] chunks, byte[] biomes, int chunkMask, int dataLength
) {
ensureWritable(wrapper, dataLength);

int largestBlockDataLength = 0;
for (int index = 0; index < chunks.length; index++) {
if ((chunkMask & 1 << index) != 0) {
largestBlockDataLength = Math.max(largestBlockDataLength,
chunks[index].getBlocks().getData().length * Short.BYTES);
}
}

byte[] encodedBlocks = largestBlockDataLength == 0 ? null : new byte[largestBlockDataLength];
ShortBuffer blockData = encodedBlocks == null ? null
: ByteBuffer.wrap(encodedBlocks).order(ByteOrder.LITTLE_ENDIAN).asShortBuffer();
for (int index = 0; index < chunks.length; index++) {
if ((chunkMask & 1 << index) != 0) {
short[] blocks = chunks[index].getBlocks().getData();
blockData.position(0);
blockData.put(blocks, 0, blocks.length);
ByteBufHelper.writeBytes(wrapper.buffer, encodedBlocks, 0, blocks.length * Short.BYTES);
}
}

for (int index = 0; index < chunks.length; index++) {
if ((chunkMask & 1 << index) != 0) {
ByteBufHelper.writeBytes(wrapper.buffer, chunks[index].getBlockLight().getData());
}
}

for (int index = 0; index < chunks.length; index++) {
if ((chunkMask & 1 << index) != 0 && chunks[index].getSkyLight() != null) {
ByteBufHelper.writeBytes(wrapper.buffer, chunks[index].getSkyLight().getData());
}
}

if (biomes != null) {
ByteBufHelper.writeBytes(wrapper.buffer, biomes);
}
}

@ApiStatus.Internal
public static void ensureWritable(PacketWrapper<?> wrapper, int additionalBytes) {
int writerIndex = ByteBufHelper.writerIndex(wrapper.buffer);
int requiredCapacity = Math.addExact(writerIndex, additionalBytes);
if (requiredCapacity > ByteBufHelper.capacity(wrapper.buffer)) {
ByteBufHelper.capacity(wrapper.buffer, requiredCapacity);
}
}

}
10 changes: 7 additions & 3 deletions ...ava/com/github/retrooper/packetevents/wrapper/play/server/WrapperPlayServerChunkData.java
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Original file line number Diff line number Diff line change
Expand Up @@ -346,9 +346,13 @@ public void write() {
ByteBufHelper.writerIndex(dataBuffer, newWriterIndex);
}
} else if (v1_8) {
NetworkChunkData data = ChunkReader_v1_8.chunksToData((Chunk_v1_8[]) chunks, column.getBiomeDataBytes());
writeShort(data.getMask());
writeByteArray(data.getData());
Chunk_v1_8[] legacyChunks = (Chunk_v1_8[]) chunks;
byte[] biomes = column.getBiomeDataBytes();
int mask = ChunkReader_v1_8.calculateChunkMask(legacyChunks, biomes != null);
int dataLength = ChunkReader_v1_8.calculateDataLength(legacyChunks, biomes, mask);
writeShort(mask);
writeVarInt(dataLength);
ChunkReader_v1_8.writeChunkData(this, legacyChunks, biomes, mask, dataLength);
return;
} else {
NetworkChunkData data = ChunkReader_v1_7.chunksToData((Chunk_v1_7[]) chunks, column.getBiomeDataBytes());
Expand Down
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