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net: remove the quadratic copy from bulk chunk assembly #204

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Merged
EverNife merged 3 commits into from
Sep 13, 2026
Merged

net: remove the quadratic copy from bulk chunk assembly #204

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2e33e13
net: assemble bulk chunk packets in one exact-size buffer
EverNife Sep 1, 2026
24b5acf
net: size the single chunk deflate buffer to zlib's bound
EverNife Sep 1, 2026
d717530
net: raise the default chunk send budget to 20 per tick
EverNife Sep 6, 2026
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247 changes: 216 additions & 31 deletions patches/net/minecraft/network/play/server/S21PacketChunkData.java.patch
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Original file line number Diff line number Diff line change
@@ -1,6 +1,6 @@
--- ../src-base/minecraft/net/minecraft/network/play/server/S21PacketChunkData.java
+++ ../src-work/minecraft/net/minecraft/network/play/server/S21PacketChunkData.java
@@ -45,7 +45,7 @@
@@ -45,13 +45,25 @@

private void deflate()
{
Expand All @@ -9,55 +9,240 @@
try
{
deflater.setInput(this.field_149278_f, 0, this.field_149278_f.length);
@@ -198,8 +198,10 @@
if (aextendedblockstorage[l] != null && (!p_149269_1_ || !aextendedblockstorage[l].isEmpty()) && (p_149269_2_ & 1 << l) != 0)
deflater.finish();
- byte[] deflated = new byte[this.field_149278_f.length];
+ byte[] deflated = new byte[deflateBound(this.field_149278_f.length)]; // Crucible
this.field_149285_h = deflater.deflate(deflated);
+
+ // Crucible start - deflate() reports a buffer that is too small by writing what fits
+ // and returning, so without this the packet would carry a truncated stream and the
+ // client would inflate it into an empty chunk without an error on either side.
+ if (!deflater.finished())
+ {
+ throw new IllegalStateException("Chunk deflate stopped short: wrote " + this.field_149285_h
+ + " of a " + deflated.length + " byte buffer for "
+ + this.field_149278_f.length + " input bytes");
+ }
+ // Crucible end
+
this.field_149281_e = deflated;
}
finally
@@ -65,6 +77,15 @@
return 196864;
}

+ // Crucible start
+ // zlib's own compressBound. At a low level deflate stores rather than compresses and the output
+ // grows past the input; deflate() would then quietly stop short and ship a truncated stream.
+ static int deflateBound(int length)
+ {
+ return length + (length >> 12) + (length >> 14) + (length >> 25) + 13;
+ }
+ // Crucible end
+
public void readPacketData(PacketBuffer p_148837_1_) throws IOException
{
this.field_149284_a = p_148837_1_.readInt();
@@ -154,102 +175,132 @@

public static S21PacketChunkData.Extracted func_149269_a(Chunk p_149269_0_, boolean p_149269_1_, int p_149269_2_)
{
- int j = 0;
- ExtendedBlockStorage[] aextendedblockstorage = p_149269_0_.getBlockStorageArray();
- int k = 0;
+ // Crucible start - measure first so the payload is allocated at its exact size and copied
+ // once, straight from the chunk
+ S21PacketChunkData.ChunkDataLayout layout = layoutOf(p_149269_0_, p_149269_1_, p_149269_2_);
S21PacketChunkData.Extracted extracted = new S21PacketChunkData.Extracted();
- byte[] abyte = field_149286_i;
+ extracted.field_150280_b = layout.sectionMask;
+ extracted.field_150281_c = layout.msbMask;
+ extracted.field_150282_a = new byte[layout.length];
+ writeChunkData(p_149269_0_, p_149269_1_, layout, extracted.field_150282_a, 0);
+ return extracted;
+ }

- if (p_149269_1_)
- {
- p_149269_0_.sendUpdates = true;
- }
+ /**
+ * Sizes the payload {@link #writeChunkData} produces for {@code chunk} without copying any block
+ * data. {@code sendAll} skips empty sections and appends the biome array, as a full chunk send
+ * does; {@code sectionFilter} is the bit mask of the sections to include.
+ */
+ public static S21PacketChunkData.ChunkDataLayout layoutOf(Chunk chunk, boolean sendAll, int sectionFilter)
+ {
+ ExtendedBlockStorage[] sections = chunk.getBlockStorageArray();
+ boolean hasSky = !chunk.worldObj.provider.hasNoSky;
+ S21PacketChunkData.ChunkDataLayout layout = new S21PacketChunkData.ChunkDataLayout();
+ int length = 0;

- int l;
-
- for (l = 0; l < aextendedblockstorage.length; ++l)
+ for (int l = 0; l < sections.length; ++l)
{
- if (aextendedblockstorage[l] != null && (!p_149269_1_ || !aextendedblockstorage[l].isEmpty()) && (p_149269_2_ & 1 << l) != 0)
+ ExtendedBlockStorage section = sections[l];
+
+ if (section != null && (!sendAll || !section.isEmpty()) && (sectionFilter & 1 << l) != 0)
{
nibblearray = aextendedblockstorage[l].getMetadataArray();
- extracted.field_150280_b |= 1 << l;
+ layout.sectionMask |= 1 << l;
+ length += section.getBlockLSBArray().length;
+ length += section.getMetadataArray().getByteLength();
+ length += section.getBlocklightArray().getByteLength();

- if (aextendedblockstorage[l].getBlockMSBArray() != null)
+ if (hasSky)
{
- extracted.field_150281_c |= 1 << l;
- ++k;
+ length += section.getSkylightArray().getByteLength();
}
+
+ if (section.getBlockMSBArray() != null)
+ {
+ layout.msbMask |= 1 << l;
+ length += section.getBlockMSBArray().getByteLength();
+ }
}
}

- for (l = 0; l < aextendedblockstorage.length; ++l)
+ if (sendAll)
{
- if (aextendedblockstorage[l] != null && (!p_149269_1_ || !aextendedblockstorage[l].isEmpty()) && (p_149269_2_ & 1 << l) != 0)
+ length += chunk.getBiomeArray().length;
+ }
+
+ layout.length = length;
+ return layout;
+ }
+
+ /**
+ * Copies the chunk payload described by {@code layout} into {@code dest} from {@code offset} on,
+ * in wire order: block ids, metadata, block light, sky light, extra ids, biomes. Returns the
+ * offset just past the written bytes.
+ */
+ public static int writeChunkData(Chunk chunk, boolean sendAll, S21PacketChunkData.ChunkDataLayout layout, byte[] dest, int offset)
+ {
+ ExtendedBlockStorage[] sections = chunk.getBlockStorageArray();
+ int j = offset;
+
+ if (sendAll)
+ {
+ chunk.sendUpdates = true;
+ }
+
+ for (int l = 0; l < sections.length; ++l)
+ {
+ if ((layout.sectionMask & 1 << l) != 0)
{
- byte[] abyte1 = aextendedblockstorage[l].getBlockLSBArray();
- System.arraycopy(abyte1, 0, abyte, j, abyte1.length);
- j += abyte1.length;
+ byte[] lsb = sections[l].getBlockLSBArray();
+ System.arraycopy(lsb, 0, dest, j, lsb.length);
+ j += lsb.length;
}
}

- NibbleArray nibblearray;
-
- for (l = 0; l < aextendedblockstorage.length; ++l)
+ for (int l = 0; l < sections.length; ++l)
{
- if (aextendedblockstorage[l] != null && (!p_149269_1_ || !aextendedblockstorage[l].isEmpty()) && (p_149269_2_ & 1 << l) != 0)
+ if ((layout.sectionMask & 1 << l) != 0)
{
- nibblearray = aextendedblockstorage[l].getMetadataArray();
- System.arraycopy(nibblearray.data, 0, abyte, j, nibblearray.data.length);
- j += nibblearray.data.length;
+ // Spigot start
+ nibblearray.copyToByteArray(abyte, j);
+ j += nibblearray.getByteLength();
+ // Spigot end
+ j = sections[l].getMetadataArray().copyToByteArray(dest, j);
}
}

@@ -208,8 +210,10 @@
if (aextendedblockstorage[l] != null && (!p_149269_1_ || !aextendedblockstorage[l].isEmpty()) && (p_149269_2_ & 1 << l) != 0)
- for (l = 0; l < aextendedblockstorage.length; ++l)
+ for (int l = 0; l < sections.length; ++l)
{
- if (aextendedblockstorage[l] != null && (!p_149269_1_ || !aextendedblockstorage[l].isEmpty()) && (p_149269_2_ & 1 << l) != 0)
+ if ((layout.sectionMask & 1 << l) != 0)
{
nibblearray = aextendedblockstorage[l].getBlocklightArray();
- nibblearray = aextendedblockstorage[l].getBlocklightArray();
- System.arraycopy(nibblearray.data, 0, abyte, j, nibblearray.data.length);
- j += nibblearray.data.length;
+ // Spigot start
+ nibblearray.copyToByteArray(abyte, j);
+ j += nibblearray.getByteLength();
+ // Spigot end
+ j = sections[l].getBlocklightArray().copyToByteArray(dest, j);
}
}

@@ -220,8 +224,10 @@
if (aextendedblockstorage[l] != null && (!p_149269_1_ || !aextendedblockstorage[l].isEmpty()) && (p_149269_2_ & 1 << l) != 0)
- if (!p_149269_0_.worldObj.provider.hasNoSky)
+ if (!chunk.worldObj.provider.hasNoSky)
{
- for (l = 0; l < aextendedblockstorage.length; ++l)
+ for (int l = 0; l < sections.length; ++l)
{
- if (aextendedblockstorage[l] != null && (!p_149269_1_ || !aextendedblockstorage[l].isEmpty()) && (p_149269_2_ & 1 << l) != 0)
+ if ((layout.sectionMask & 1 << l) != 0)
{
nibblearray = aextendedblockstorage[l].getSkylightArray();
- nibblearray = aextendedblockstorage[l].getSkylightArray();
- System.arraycopy(nibblearray.data, 0, abyte, j, nibblearray.data.length);
- j += nibblearray.data.length;
+ // Spigot start
+ nibblearray.copyToByteArray(abyte, j);
+ j += nibblearray.getByteLength();
+ // Spigot end
+ j = sections[l].getSkylightArray().copyToByteArray(dest, j);
}
}
}
@@ -233,8 +239,10 @@
if (aextendedblockstorage[l] != null && (!p_149269_1_ || !aextendedblockstorage[l].isEmpty()) && aextendedblockstorage[l].getBlockMSBArray() != null && (p_149269_2_ & 1 << l) != 0)
{
nibblearray = aextendedblockstorage[l].getBlockMSBArray();

- if (k > 0)
+ for (int l = 0; l < sections.length; ++l)
{
- for (l = 0; l < aextendedblockstorage.length; ++l)
+ if ((layout.msbMask & 1 << l) != 0)
{
- if (aextendedblockstorage[l] != null && (!p_149269_1_ || !aextendedblockstorage[l].isEmpty()) && aextendedblockstorage[l].getBlockMSBArray() != null && (p_149269_2_ & 1 << l) != 0)
- {
- nibblearray = aextendedblockstorage[l].getBlockMSBArray();
- System.arraycopy(nibblearray.data, 0, abyte, j, nibblearray.data.length);
- j += nibblearray.data.length;
+ // Spigot start
+ nibblearray.copyToByteArray(abyte, j);
+ j += nibblearray.getByteLength();
+ // Spigot end
}
- }
+ j = sections[l].getBlockMSBArray().copyToByteArray(dest, j);
}
}

- if (p_149269_1_)
+ if (sendAll)
{
- byte[] abyte2 = p_149269_0_.getBiomeArray();
- System.arraycopy(abyte2, 0, abyte, j, abyte2.length);
- j += abyte2.length;
+ byte[] biomes = chunk.getBiomeArray();
+ System.arraycopy(biomes, 0, dest, j, biomes.length);
+ j += biomes.length;
}

- extracted.field_150282_a = new byte[j];
- System.arraycopy(abyte, 0, extracted.field_150282_a, 0, j);
- return extracted;
+ return j;
}
+ // Crucible end

public void processPacket(INetHandler p_148833_1_)
{
@@ -286,6 +337,14 @@
return this.field_149279_g;
}

+ /** Section masks and payload length of one chunk, as {@link #layoutOf} measures them. */
+ public static class ChunkDataLayout
+ {
+ public int sectionMask;
+ public int msbMask;
+ public int length;
+ }
+
public static class Extracted
{
public byte[] field_150282_a;
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