From 0000000000000000000000000000000000000000 Mon Sep 17 00:00:00 2001
From: Spottedleaf <Spottedleaf@users.noreply.github.com>
Date: Sat, 15 Jun 2019 08:54:33 -0700
Subject: [PATCH] Fix World#isChunkGenerated calls

Optimize World#loadChunk() too
This patch also adds a chunk status cache on region files (note that
its only purpose is to cache the status on DISK)

diff --git a/src/main/java/net/minecraft/server/ChunkProviderServer.java b/src/main/java/net/minecraft/server/ChunkProviderServer.java
index 0000000000000000000000000000000000000000..0000000000000000000000000000000000000000 100644
--- a/src/main/java/net/minecraft/server/ChunkProviderServer.java
+++ b/src/main/java/net/minecraft/server/ChunkProviderServer.java
@@ -0,0 +0,0 @@ public class ChunkProviderServer extends IChunkProvider {
     private final WorldServer world;
     public final Thread serverThread; // Paper - private -> public
     private final LightEngineThreaded lightEngine;
-    private final ChunkProviderServer.a serverThreadQueue;
+    public final ChunkProviderServer.a serverThreadQueue; // Paper private -> public
     public final PlayerChunkMap playerChunkMap;
     private final WorldPersistentData worldPersistentData;
     private long lastTickTime;
@@ -0,0 +0,0 @@ public class ChunkProviderServer extends IChunkProvider {
 
         return ret;
     }
+
+    @Nullable
+    public IChunkAccess getChunkAtImmediately(int x, int z) {
+        long k = ChunkCoordIntPair.pair(x, z);
+
+        // Note: Bypass cache to make this MT-Safe
+
+        PlayerChunk playerChunk = this.getChunk(k);
+        if (playerChunk == null) {
+            return null;
+        }
+
+        return playerChunk.getAvailableChunkNow();
+
+    }
     // Paper end
 
     @Nullable
diff --git a/src/main/java/net/minecraft/server/ChunkRegionLoader.java b/src/main/java/net/minecraft/server/ChunkRegionLoader.java
index 0000000000000000000000000000000000000000..0000000000000000000000000000000000000000 100644
--- a/src/main/java/net/minecraft/server/ChunkRegionLoader.java
+++ b/src/main/java/net/minecraft/server/ChunkRegionLoader.java
@@ -0,0 +0,0 @@ public class ChunkRegionLoader {
     }
     // Paper end
 
+    // Paper start
+    public static ChunkStatus getStatus(NBTTagCompound compound) {
+        if (compound == null) {
+            return null;
+        }
+
+        // Note: Copied from below
+        return ChunkStatus.getStatus(compound.getCompound("Level").getString("Status"));
+    }
+    // Paper end
+
     public static ChunkStatus.Type a(@Nullable NBTTagCompound nbttagcompound) {
         if (nbttagcompound != null) {
             ChunkStatus chunkstatus = ChunkStatus.a(nbttagcompound.getCompound("Level").getString("Status"));
diff --git a/src/main/java/net/minecraft/server/ChunkStatus.java b/src/main/java/net/minecraft/server/ChunkStatus.java
index 0000000000000000000000000000000000000000..0000000000000000000000000000000000000000 100644
--- a/src/main/java/net/minecraft/server/ChunkStatus.java
+++ b/src/main/java/net/minecraft/server/ChunkStatus.java
@@ -0,0 +0,0 @@ public class ChunkStatus {
         return this.s;
     }
 
+    public ChunkStatus getPreviousStatus() { return this.e(); } // Paper - OBFHELPER
     public ChunkStatus e() {
         return this.u;
     }
@@ -0,0 +0,0 @@ public class ChunkStatus {
         return this.y;
     }
 
+    // Paper start
+    public static ChunkStatus getStatus(String name) {
+        try {
+            // We need this otherwise we return EMPTY for invalid names
+            MinecraftKey key = new MinecraftKey(name);
+            return IRegistry.CHUNK_STATUS.getOptional(key).orElse(null);
+        } catch (Exception ex) {
+            return null; // invalid name
+        }
+    }
+    // Paper end
     public static ChunkStatus a(String s) {
         return (ChunkStatus) IRegistry.CHUNK_STATUS.get(MinecraftKey.a(s));
     }
diff --git a/src/main/java/net/minecraft/server/IChunkLoader.java b/src/main/java/net/minecraft/server/IChunkLoader.java
index 0000000000000000000000000000000000000000..0000000000000000000000000000000000000000 100644
--- a/src/main/java/net/minecraft/server/IChunkLoader.java
+++ b/src/main/java/net/minecraft/server/IChunkLoader.java
@@ -0,0 +0,0 @@ import javax.annotation.Nullable;
 
 public class IChunkLoader implements AutoCloseable {
 
-    private final IOWorker a;
+    private final IOWorker a; public IOWorker getIOWorker() { return a; } // Paper - OBFHELPER
     protected final DataFixer b;
     @Nullable
     private PersistentStructureLegacy c;
diff --git a/src/main/java/net/minecraft/server/PlayerChunk.java b/src/main/java/net/minecraft/server/PlayerChunk.java
index 0000000000000000000000000000000000000000..0000000000000000000000000000000000000000 100644
--- a/src/main/java/net/minecraft/server/PlayerChunk.java
+++ b/src/main/java/net/minecraft/server/PlayerChunk.java
@@ -0,0 +0,0 @@ public class PlayerChunk {
         Either<IChunkAccess, PlayerChunk.Failure> either = (Either<IChunkAccess, PlayerChunk.Failure>) statusFuture.getNow(null);
         return either == null ? null : (Chunk) either.left().orElse(null);
     }
+
+    public IChunkAccess getAvailableChunkNow() {
+        // TODO can we just getStatusFuture(EMPTY)?
+        for (ChunkStatus curr = ChunkStatus.FULL, next = curr.getPreviousStatus(); curr != next; curr = next, next = next.getPreviousStatus()) {
+            CompletableFuture<Either<IChunkAccess, PlayerChunk.Failure>> future = this.getStatusFutureUnchecked(curr);
+            Either<IChunkAccess, PlayerChunk.Failure> either = future.getNow(null);
+            if (either == null || !either.left().isPresent()) {
+                continue;
+            }
+            return either.left().get();
+        }
+        return null;
+    }
     // Paper end
 
     public CompletableFuture<Either<IChunkAccess, PlayerChunk.Failure>> getStatusFutureUnchecked(ChunkStatus chunkstatus) {
diff --git a/src/main/java/net/minecraft/server/PlayerChunkMap.java b/src/main/java/net/minecraft/server/PlayerChunkMap.java
index 0000000000000000000000000000000000000000..0000000000000000000000000000000000000000 100644
--- a/src/main/java/net/minecraft/server/PlayerChunkMap.java
+++ b/src/main/java/net/minecraft/server/PlayerChunkMap.java
@@ -0,0 +0,0 @@ public class PlayerChunkMap extends IChunkLoader implements PlayerChunk.d {
     }
 
     @Nullable
-    private NBTTagCompound readChunkData(ChunkCoordIntPair chunkcoordintpair) throws IOException {
+    public NBTTagCompound readChunkData(ChunkCoordIntPair chunkcoordintpair) throws IOException { // Paper - private -> public
         NBTTagCompound nbttagcompound = this.read(chunkcoordintpair);
+        // Paper start - Cache chunk status on disk
+        if (nbttagcompound == null) {
+            return null;
+        }
+
+        nbttagcompound = this.getChunkData(this.world.getTypeKey(), this.l, nbttagcompound, chunkcoordintpair, world); // CraftBukkit
+        if (nbttagcompound == null) {
+            return null;
+        }
+
+        this.updateChunkStatusOnDisk(chunkcoordintpair, nbttagcompound);
+
+        return nbttagcompound;
+        // Paper end
+    }
+
+    // Paper start - chunk status cache "api"
+    public ChunkStatus getChunkStatusOnDiskIfCached(ChunkCoordIntPair chunkPos) {
+        RegionFile regionFile = this.getIOWorker().getRegionFileCache().getRegionFileIfLoaded(chunkPos);
+
+        return regionFile == null ? null : regionFile.getStatusIfCached(chunkPos.x, chunkPos.z);
+    }
+
+    public ChunkStatus getChunkStatusOnDisk(ChunkCoordIntPair chunkPos) throws IOException {
+        RegionFile regionFile = this.getIOWorker().getRegionFileCache().getFile(chunkPos, true);
+
+        if (regionFile == null || !regionFile.chunkExists(chunkPos)) {
+            return null;
+        }
+
+        ChunkStatus status = regionFile.getStatusIfCached(chunkPos.x, chunkPos.z);
+
+        if (status != null) {
+            return status;
+        }
+
+        this.readChunkData(chunkPos);
 
-        return nbttagcompound == null ? null : this.getChunkData(this.world.getTypeKey(), this.l, nbttagcompound, chunkcoordintpair, world); // CraftBukkit
+        return regionFile.getStatusIfCached(chunkPos.x, chunkPos.z);
     }
 
+    public void updateChunkStatusOnDisk(ChunkCoordIntPair chunkPos, @Nullable NBTTagCompound compound) throws IOException {
+        RegionFile regionFile = this.getIOWorker().getRegionFileCache().getFile(chunkPos, false);
+
+        regionFile.setStatus(chunkPos.x, chunkPos.z, ChunkRegionLoader.getStatus(compound));
+    }
+
+    public IChunkAccess getUnloadingChunk(int chunkX, int chunkZ) {
+        PlayerChunk chunkHolder = this.pendingUnload.get(ChunkCoordIntPair.pair(chunkX, chunkZ));
+        return chunkHolder == null ? null : chunkHolder.getAvailableChunkNow();
+    }
+    // Paper end
+
     boolean isOutsideOfRange(ChunkCoordIntPair chunkcoordintpair) {
         // Spigot start
         return isOutsideOfRange(chunkcoordintpair, false);
diff --git a/src/main/java/net/minecraft/server/RegionFile.java b/src/main/java/net/minecraft/server/RegionFile.java
index 0000000000000000000000000000000000000000..0000000000000000000000000000000000000000 100644
--- a/src/main/java/net/minecraft/server/RegionFile.java
+++ b/src/main/java/net/minecraft/server/RegionFile.java
@@ -0,0 +0,0 @@ public class RegionFile implements AutoCloseable {
     private final RegionFileBitSet freeSectors;
     public final File file;
 
+    // Paper start - Cache chunk status
+    private final ChunkStatus[] statuses = new ChunkStatus[32 * 32];
+
+    private boolean closed;
+
+    // invoked on write/read
+    public void setStatus(int x, int z, ChunkStatus status) {
+        if (this.closed) {
+            // We've used an invalid region file.
+            throw new IllegalStateException("RegionFile is closed");
+        }
+        this.statuses[this.getChunkLocation(new ChunkCoordIntPair(x, z))] = status;
+    }
+
+    public ChunkStatus getStatusIfCached(int x, int z) {
+        if (this.closed) {
+            // We've used an invalid region file.
+            throw new IllegalStateException("RegionFile is closed");
+        }
+        final int location = this.getChunkLocation(new ChunkCoordIntPair(x, z));
+        return this.statuses[location];
+    }
+    // Paper end
+
     public RegionFile(File file, File file1, boolean flag) throws IOException {
         this(file.toPath(), file1.toPath(), RegionFileCompression.b, flag);
     }
@@ -0,0 +0,0 @@ public class RegionFile implements AutoCloseable {
         return this.getOffset(chunkcoordintpair) != 0;
     }
 
+    private final int getChunkLocation(ChunkCoordIntPair chunkcoordintpair) { return this.g(chunkcoordintpair); } // Paper - OBFHELPER
     private static int g(ChunkCoordIntPair chunkcoordintpair) {
         return chunkcoordintpair.j() + chunkcoordintpair.k() * 32;
     }
 
     public void close() throws IOException {
+        this.closed = true; // Paper
         try {
             this.d();
         } finally {
diff --git a/src/main/java/net/minecraft/server/RegionFileCache.java b/src/main/java/net/minecraft/server/RegionFileCache.java
index 0000000000000000000000000000000000000000..0000000000000000000000000000000000000000 100644
--- a/src/main/java/net/minecraft/server/RegionFileCache.java
+++ b/src/main/java/net/minecraft/server/RegionFileCache.java
@@ -0,0 +0,0 @@ public final class RegionFileCache implements AutoCloseable {
         this.c = flag;
     }
 
-    private RegionFile getFile(ChunkCoordIntPair chunkcoordintpair, boolean existingOnly) throws IOException { // CraftBukkit
+
+    // Paper start
+    public RegionFile getRegionFileIfLoaded(ChunkCoordIntPair chunkcoordintpair) {
+        return this.cache.getAndMoveToFirst(ChunkCoordIntPair.pair(chunkcoordintpair.getRegionX(), chunkcoordintpair.getRegionZ()));
+    }
+
+    // Paper end
+    public RegionFile getFile(ChunkCoordIntPair chunkcoordintpair, boolean existingOnly) throws IOException { // CraftBukkit // Paper - private >  public
         long i = ChunkCoordIntPair.pair(chunkcoordintpair.getRegionX(), chunkcoordintpair.getRegionZ());
         RegionFile regionfile = (RegionFile) this.cache.getAndMoveToFirst(i);
 
@@ -0,0 +0,0 @@ public final class RegionFileCache implements AutoCloseable {
 
         try {
             NBTCompressedStreamTools.a(nbttagcompound, (DataOutput) dataoutputstream);
-            regionfile.setOversized(chunkcoordintpair.x, chunkcoordintpair.z, false); // We don't do this anymore
+            regionfile.setStatus(chunkcoordintpair.x, chunkcoordintpair.z, ChunkRegionLoader.getStatus(nbttagcompound)); // Paper - cache status on disk
+            regionfile.setOversized(chunkcoordintpair.x, chunkcoordintpair.z, false);
         } catch (Throwable throwable1) {
             throwable = throwable1;
             throw throwable1;
diff --git a/src/main/java/org/bukkit/craftbukkit/CraftWorld.java b/src/main/java/org/bukkit/craftbukkit/CraftWorld.java
index 0000000000000000000000000000000000000000..0000000000000000000000000000000000000000 100644
--- a/src/main/java/org/bukkit/craftbukkit/CraftWorld.java
+++ b/src/main/java/org/bukkit/craftbukkit/CraftWorld.java
@@ -0,0 +0,0 @@ import java.util.Objects;
 import java.util.Random;
 import java.util.Set;
 import java.util.UUID;
+import java.util.concurrent.CompletableFuture;
 import java.util.function.Predicate;
 import java.util.stream.Collectors;
 import net.minecraft.server.ArraySetSorted;
@@ -0,0 +0,0 @@ public class CraftWorld implements World {
 
     @Override
     public boolean isChunkGenerated(int x, int z) {
+        // Paper start - Fix this method
+        if (!Bukkit.isPrimaryThread()) {
+            return CompletableFuture.supplyAsync(() -> {
+                return CraftWorld.this.isChunkGenerated(x, z);
+            }, world.getChunkProvider().serverThreadQueue).join();
+        }
+        IChunkAccess chunk = world.getChunkProvider().getChunkAtImmediately(x, z);
+        if (chunk == null) {
+            chunk = world.getChunkProvider().playerChunkMap.getUnloadingChunk(x, z);
+        }
+        if (chunk != null) {
+            return chunk instanceof ProtoChunkExtension || chunk instanceof net.minecraft.server.Chunk;
+        }
         try {
-            return world.getChunkProvider().getChunkAtIfCachedImmediately(x, z) != null || world.getChunkProvider().playerChunkMap.read(new ChunkCoordIntPair(x, z)) != null; // Paper (TODO check if the first part can be removed)
+            return world.getChunkProvider().playerChunkMap.getChunkStatusOnDisk(new ChunkCoordIntPair(x, z)) == ChunkStatus.FULL;
+            // Paper end
         } catch (IOException ex) {
             throw new RuntimeException(ex);
         }
@@ -0,0 +0,0 @@ public class CraftWorld implements World {
     @Override
     public boolean loadChunk(int x, int z, boolean generate) {
         org.spigotmc.AsyncCatcher.catchOp("chunk load"); // Spigot
-        IChunkAccess chunk = world.getChunkProvider().getChunkAt(x, z, generate || isChunkGenerated(x, z) ? ChunkStatus.FULL : ChunkStatus.EMPTY, true); // Paper
+        // Paper start - Optimize this method
+        ChunkCoordIntPair chunkPos = new ChunkCoordIntPair(x, z);
 
-        // If generate = false, but the chunk already exists, we will get this back.
-        if (chunk instanceof ProtoChunkExtension) {
-            // We then cycle through again to get the full chunk immediately, rather than after the ticket addition
-            chunk = world.getChunkProvider().getChunkAt(x, z, ChunkStatus.FULL, true);
-        }
+        if (!generate) {
 
-        if (chunk instanceof net.minecraft.server.Chunk) {
-            world.getChunkProvider().addTicket(TicketType.PLUGIN, new ChunkCoordIntPair(x, z), 1, Unit.INSTANCE);
-            return true;
+            IChunkAccess immediate = world.getChunkProvider().getChunkAtImmediately(x, z);
+            if (immediate == null) {
+                immediate = world.getChunkProvider().playerChunkMap.getUnloadingChunk(x, z);
+            }
+            if (immediate != null) {
+                if (!(immediate instanceof ProtoChunkExtension) && !(immediate instanceof net.minecraft.server.Chunk)) {
+                    return false; // not full status
+                }
+                world.getChunkProvider().addTicket(TicketType.PLUGIN, chunkPos, 1, Unit.INSTANCE);
+                world.getChunkAt(x, z); // make sure we're at ticket level 32 or lower
+                return true;
+            }
+
+            net.minecraft.server.RegionFile file;
+            try {
+                file = world.getChunkProvider().playerChunkMap.getIOWorker().getRegionFileCache().getFile(chunkPos, false);
+            } catch (IOException ex) {
+                throw new RuntimeException(ex);
+            }
+
+            ChunkStatus status = file.getStatusIfCached(x, z);
+            if (!file.chunkExists(chunkPos) || (status != null && status != ChunkStatus.FULL)) {
+                return false;
+            }
+
+            IChunkAccess chunk = world.getChunkProvider().getChunkAt(x, z, ChunkStatus.EMPTY, true);
+            if (!(chunk instanceof ProtoChunkExtension) && !(chunk instanceof net.minecraft.server.Chunk)) {
+                return false;
+            }
+
+            // fall through to load
+            // we do this so we do not re-read the chunk data on disk
         }
 
-        return false;
+        world.getChunkProvider().addTicket(TicketType.PLUGIN, chunkPos, 1, Unit.INSTANCE);
+        world.getChunkProvider().getChunkAt(x, z, ChunkStatus.FULL, true);
+        return true;
+        // Paper end
     }
 
     @Override
