From a39de7d7d245b4bef3b845452dfcc00e9999232d Mon Sep 17 00:00:00 2001
From: David Choo <davchoo@users.noreply.github.com>
Date: Fri, 14 Jan 2022 14:57:59 -0500
Subject: [PATCH] Fix ArrayIndexOutOfBoundsException for worlds lower than -64
 (#2759)

* Fix ArrayIndexOutOfBoundsException for worlds lower than -64

`chunkSize` is Java section count while `sectionCount` is the Bedrock section count

* Send biomes for air sections while also staying within limits

.-.

* Move protocol version check to variable
---
 .../JavaLevelChunkWithLightTranslator.java    | 37 +++++++++----------
 1 file changed, 18 insertions(+), 19 deletions(-)

diff --git a/core/src/main/java/org/geysermc/geyser/translator/protocol/java/level/JavaLevelChunkWithLightTranslator.java b/core/src/main/java/org/geysermc/geyser/translator/protocol/java/level/JavaLevelChunkWithLightTranslator.java
index 75e0390c3..97b826473 100644
--- a/core/src/main/java/org/geysermc/geyser/translator/protocol/java/level/JavaLevelChunkWithLightTranslator.java
+++ b/core/src/main/java/org/geysermc/geyser/translator/protocol/java/level/JavaLevelChunkWithLightTranslator.java
@@ -309,32 +309,31 @@ public class JavaLevelChunkWithLightTranslator extends PacketTranslator<Clientbo
                 }
             }
 
-            // At this point we're dealing with Bedrock chunk sections
+            // As of 1.17.10, Bedrock hardcodes to always read 32 biome sections
+            // As of 1.18, this hardcode was lowered to 25
+            boolean isNewVersion = session.getUpstream().getProtocolVersion() >= Bedrock_v475.V475_CODEC.getProtocolVersion();
+            int biomeCount = isNewVersion ? 25 : 32;
             int dimensionOffset = (overworld ? MINIMUM_ACCEPTED_HEIGHT_OVERWORLD : MINIMUM_ACCEPTED_HEIGHT) >> 4;
-            for (int i = 0; i < chunkSize; i++) {
+            for (int i = 0; i < biomeCount; i++) {
                 int biomeYOffset = dimensionOffset + i;
                 if (biomeYOffset < yOffset) {
-                    // Ignore this biome section since it goes above or below the height of the Java world
+                    // Ignore this biome section since it goes below the height of the Java world
                     byteBuf.writeBytes(ChunkUtils.EMPTY_BIOME_DATA);
                     continue;
                 }
-                BiomeTranslator.toNewBedrockBiome(session, javaBiomes[i + (dimensionOffset - yOffset)]).writeToNetwork(byteBuf);
-            }
+                if (biomeYOffset >= (chunkSize + yOffset)) {
+                    // This biome section goes above the height of the Java world
+                    if (isNewVersion) {
+                        // A header that says to carry on the biome data from the previous chunk
+                        // This notably fixes biomes in the End
+                        byteBuf.writeByte((127 << 1) | 1);
+                    } else {
+                        byteBuf.writeBytes(ChunkUtils.EMPTY_BIOME_DATA);
+                    }
+                    continue;
+                }
 
-            // As of 1.17.10, Bedrock hardcodes to always read 32 biome sections
-            // As of 1.18, this hardcode was lowered to 25
-            if (session.getUpstream().getProtocolVersion() >= Bedrock_v475.V475_CODEC.getProtocolVersion()) {
-                int remainingEmptyBiomes = 25 - chunkSize;
-                for (int i = 0; i < remainingEmptyBiomes; i++) {
-                    // A header that says to carry on the biome data from the previous chunk
-                    // This notably fixes biomes in the End
-                    byteBuf.writeByte((127 << 1) | 1);
-                }
-            } else {
-                int remainingEmptyBiomes = 32 - chunkSize;
-                for (int i = 0; i < remainingEmptyBiomes; i++) {
-                    byteBuf.writeBytes(ChunkUtils.EMPTY_BIOME_DATA);
-                }
+                BiomeTranslator.toNewBedrockBiome(session, javaBiomes[i + (dimensionOffset - yOffset)]).writeToNetwork(byteBuf);
             }
 
             byteBuf.writeByte(0); // Border blocks - Edu edition only