Don't thread single chunk compression. Fixes BUKKIT-2927

Packet 51 is used to send updates about large changes to single chunks
and to remove chunks from the client when they get out of range. In the
first case a single packet object is created and queued for all relevant
players. With our current chunk compression scheme this means the first
player to have the packet processed will start the compression and get the
packet correctly but the rest will get garbage.

Since this packet never contains much data it is better to simply handle
compression of it on the main thread like vanilla does instead of putting in
locks and dealing with their overhead and complexity.

src/main/java/net/minecraft/server/Packet51MapChunk.java

@@ -15,17 +15,9 @@ public class Packet51MapChunk extends Packet {
     public int d;
     private byte[] buffer;
     private byte[] inflatedBuffer;
-    private boolean e;
+    public boolean e;
     private int size;
     private static byte[] buildBuffer = new byte[196864];
-    // CraftBukkit start
-    static final ThreadLocal<Deflater> localDeflater = new ThreadLocal<Deflater>() {
-        @Override
-        protected Deflater initialValue() {
-            return new Deflater(Deflater.DEFAULT_COMPRESSION);
-        }
-    };
-    // CraftBukkit end
 
     public Packet51MapChunk() {
         this.lowPriority = true;
@@ -37,12 +29,11 @@ public class Packet51MapChunk extends Packet {
         this.b = chunk.z;
         this.e = flag;
         ChunkMap chunkmap = a(chunk, flag, i);
-        // Deflater deflater = new Deflater(-1); // CraftBukkit
+        Deflater deflater = new Deflater(-1);
 
         this.d = chunkmap.c;
         this.c = chunkmap.b;
 
-        /* CraftBukkit start - moved to compress()
         try {
             this.inflatedBuffer = chunkmap.a;
             deflater.setInput(chunkmap.a, 0, chunkmap.a.length);
@@ -52,28 +43,9 @@ public class Packet51MapChunk extends Packet {
         } finally {
             deflater.end();
         }
-        */
-        this.inflatedBuffer = chunkmap.a;
     }
 
-    // Add compression method
-    public void compress() {
-        if (this.buffer != null) {
-            return;
-        }
-
-        Deflater deflater = localDeflater.get();
-        deflater.reset();
-        deflater.setInput(this.inflatedBuffer);
-        deflater.finish();
-
-        this.buffer = new byte[this.inflatedBuffer.length + 100];
-
-        this.size = deflater.deflate(this.buffer);
-    }
-    // CraftBukkit end
-
-    public void a(DataInputStream datainputstream) throws IOException {
+    public void a(DataInputStream datainputstream) throws IOException { // CraftBukkit - throws IOException
         this.a = datainputstream.readInt();
         this.b = datainputstream.readInt();
         this.e = datainputstream.readBoolean();
@@ -113,7 +85,6 @@ public class Packet51MapChunk extends Packet {
     }
 
     public void a(DataOutputStream dataoutputstream) throws IOException { // CraftBukkit - throws IOException
-        compress(); // CraftBukkit
         dataoutputstream.writeInt(this.a);
         dataoutputstream.writeInt(this.b);
         dataoutputstream.writeBoolean(this.e);