Minor optimizations for chunk retrieval

src/main/java/org/embeddedt/vintagefix/chunk/VintageChunkMap.java

@@ -0,0 +1,65 @@
+package org.embeddedt.vintagefix.chunk;
+
+import it.unimi.dsi.fastutil.longs.Long2ObjectOpenHashMap;
+import net.minecraft.util.math.ChunkPos;
+import net.minecraft.world.chunk.Chunk;
+
+/**
+ * This class implements a small LRU cache on top of Long2ObjectOpenHashMap to enable
+ * faster chunk lookups if the same chunk is retrieved many times.
+ */
+public class VintageChunkMap extends Long2ObjectOpenHashMap<Chunk> {
+    private static final int CACHE_SIZE = 4;
+    private final long[] cachedChunkPositions = new long[CACHE_SIZE];
+    private final Chunk[] cachedChunks = new Chunk[CACHE_SIZE];
+
+    public VintageChunkMap() {
+        super(8192);
+    }
+
+    @Override
+    public Chunk get(long key) {
+        for (int i = 0; i < 4; ++i) {
+            // Consolidate the scan into one comparison, allowing the JVM to better optimize the function
+            // This is considerably faster than scanning two arrays side-by-side
+            if (key == cachedChunkPositions[i]) {
+                Chunk chunk = this.cachedChunks[i];
+
+                // If the chunk exists for the key, return the result
+                // We also check that the position matches, in case mods try to access
+                // chunks on the wrong thread
+                if (chunk != null && ChunkPos.asLong(chunk.x, chunk.z) == key) {
+                    return chunk;
+                }
+            }
+        }
+
+        Chunk chunk = super.get(key);
+
+        if (chunk != null) {
+            this.addToCache(key, chunk);
+        }
+
+        return chunk;
+    }
+
+    @Override
+    public Chunk remove(long k) {
+        for (int i = 0; i < 4; ++i) {
+            if (k == cachedChunkPositions[i]) {
+                cachedChunks[i] = null;
+            }
+        }
+        return super.remove(k);
+    }
+
+    private void addToCache(long key, Chunk chunk) {
+        for (int i = CACHE_SIZE - 1; i > 0; --i) {
+            this.cachedChunkPositions[i] = this.cachedChunkPositions[i - 1];
+            this.cachedChunks[i] = this.cachedChunks[i - 1];
+        }
+
+        this.cachedChunkPositions[0] = key;
+        this.cachedChunks[0] = chunk;
+    }
+}

src/main/java/org/embeddedt/vintagefix/mixin/chunk_access/ChunkMixin.java

@@ -0,0 +1,42 @@
+package org.embeddedt.vintagefix.mixin.chunk_access;
+
+import net.minecraft.block.state.IBlockState;
+import net.minecraft.init.Blocks;
+import net.minecraft.util.math.BlockPos;
+import net.minecraft.world.World;
+import net.minecraft.world.chunk.Chunk;
+import net.minecraft.world.chunk.storage.ExtendedBlockStorage;
+import org.spongepowered.asm.mixin.Final;
+import org.spongepowered.asm.mixin.Mixin;
+import org.spongepowered.asm.mixin.Overwrite;
+import org.spongepowered.asm.mixin.Shadow;
+
+@Mixin(Chunk.class)
+public class ChunkMixin {
+    @Shadow
+    @Final
+    private ExtendedBlockStorage[] storageArrays;
+
+    @Shadow
+    @Final
+    public static ExtendedBlockStorage NULL_BLOCK_STORAGE;
+
+    private static final IBlockState DEFAULT_BLOCK_STATE = Blocks.AIR.getDefaultState();
+
+    /**
+     * @reason Reduce method size to help the JVM inline
+     * @author JellySquid
+     */
+    @Overwrite
+    public IBlockState getBlockState(int x, int y, int z) {
+        if (y >= 0 && (y >> 4) < this.storageArrays.length) {
+            ExtendedBlockStorage section = this.storageArrays[y >> 4];
+
+            if (section != NULL_BLOCK_STORAGE) {
+                return section.get(x & 15, y & 15, z & 15);
+            }
+        }
+
+        return DEFAULT_BLOCK_STATE;
+    }
+}

src/main/java/org/embeddedt/vintagefix/mixin/chunk_access/ChunkProviderClientMixin.java

@@ -0,0 +1,14 @@
+package org.embeddedt.vintagefix.mixin.chunk_access;
+
+import it.unimi.dsi.fastutil.longs.Long2ObjectMap;
+import net.minecraft.client.multiplayer.ChunkProviderClient;
+import net.minecraft.world.chunk.Chunk;
+import org.embeddedt.vintagefix.chunk.VintageChunkMap;
+import org.spongepowered.asm.mixin.Final;
+import org.spongepowered.asm.mixin.Mixin;
+import org.spongepowered.asm.mixin.Shadow;
+
+@Mixin(ChunkProviderClient.class)
+public class ChunkProviderClientMixin {
+    @Shadow @Final private final Long2ObjectMap<Chunk> loadedChunks = new VintageChunkMap();
+}

src/main/java/org/embeddedt/vintagefix/mixin/chunk_access/ChunkProviderServerMixin.java

@@ -0,0 +1,16 @@
+package org.embeddedt.vintagefix.mixin.chunk_access;
+
+import it.unimi.dsi.fastutil.longs.Long2ObjectMap;
+import net.minecraft.world.chunk.Chunk;
+import net.minecraft.world.gen.ChunkProviderServer;
+import org.embeddedt.vintagefix.chunk.VintageChunkMap;
+import org.spongepowered.asm.mixin.Final;
+import org.spongepowered.asm.mixin.Mixin;
+import org.spongepowered.asm.mixin.Shadow;
+
+@Mixin(ChunkProviderServer.class)
+public class ChunkProviderServerMixin {
+    @Shadow
+    @Final
+    private final Long2ObjectMap<Chunk> loadedChunks = new VintageChunkMap();
+}