Fix pooled buffer leak resulting in dynmap black spots - Fixes #3386

Dynmap accessed the raw bytes because it utilized NBT locally, but the
NBTTagcompound was garbage collected while the bytes were still being used.

This will return getBytes() back to being safe, and add a new PoolSafe method
that will prevent the additional allocations for general chunk loading.

Also fixed applyPatches for people with paths in their working directory
if they have mcdev sources built.

Spigot-Server-Patches/Optimize-NibbleArray-to-use-pooled-buffers.patch

@@ -12,6 +12,32 @@ diff --git a/src/main/java/net/minecraft/server/ChunkRegionLoader.java b/src/mai
 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 {
+             if (flag) {
+                 if (nbttagcompound2.hasKeyOfType("BlockLight", 7)) {
+                     // Paper start - delay this task since we're executing off-main
+-                    NibbleArray blockLight = new NibbleArray(nbttagcompound2.getByteArray("BlockLight"));
++                    // Pool safe get and clean
++                    NBTTagByteArray blockLightArray = nbttagcompound2.getByteArrayTag("BlockLight");
++                    // NibbleArray will copy the data in the ctor
++                    NibbleArray blockLight = new NibbleArray(blockLightArray.getBytesPoolSafe());
++                    blockLightArray.cleanPooledBytes();
+                     // Note: We move the block light nibble array creation here for perf & in case the compound is modified
+                     tasksToExecuteOnMain.add(() -> {
+                         lightengine.a(EnumSkyBlock.BLOCK, SectionPosition.a(chunkcoordintpair, b0), blockLight);
+@@ -0,0 +0,0 @@ public class ChunkRegionLoader {
+ 
+                 if (flag2 && nbttagcompound2.hasKeyOfType("SkyLight", 7)) {
+                     // Paper start - delay this task since we're executing off-main
+-                    NibbleArray skyLight = new NibbleArray(nbttagcompound2.getByteArray("SkyLight"));
++                    // Pool safe get and clean
++                    NBTTagByteArray skyLightArray = nbttagcompound2.getByteArrayTag("SkyLight");
++                    // NibbleArray will copy the data in the ctor
++                    NibbleArray skyLight = new NibbleArray(skyLightArray.getBytesPoolSafe());
++                    skyLightArray.cleanPooledBytes();
+                     // Note: We move the block light nibble array creation here for perf & in case the compound is modified
+                     tasksToExecuteOnMain.add(() -> {
+                         lightengine.a(EnumSkyBlock.SKY, SectionPosition.a(chunkcoordintpair, b0), skyLight);
 @@ -0,0 +0,0 @@ public class ChunkRegionLoader {
                  }
  
@@ -73,13 +99,74 @@ index 0000000000000000000000000000000000000000..00000000000000000000000000000000
 +            NBTTagByteArray nbt = new NBTTagByteArray(abyte);
 +            if (abyte.length == 2048) {
 +                // register cleaner
-+                MCUtil.registerCleaner(nbt, abyte, NibbleArray::releaseBytes);
++                nbt.cleaner = MCUtil.registerCleaner(nbt, abyte, NibbleArray::releaseBytes);
 +            }
 +            return nbt;
 +            // Paper end
          }
  
          @Override
+@@ -0,0 +0,0 @@ public class NBTTagByteArray extends NBTList<NBTTagByte> {
+     }
+ 
+     public byte[] getBytes() {
++        // Paper start
++        Runnable cleaner = this.cleaner;
++        if (cleaner != null) { // This will only be possible for 2048 byte arrays
++            // cleaners are thread safe if it tries to run twice, if getBytes is accessed concurrently, worse
++            // case is multiple clones
++            this.data = this.data.clone();
++            this.cleaner = null;
++            cleaner.run();
++        }
++        if (this.data == null) {
++            new Throwable("Horrible thing happened! Something hooked into Chunk Loading internals and accessed NBT after chunk was done loading. Please tell plugin to stop doing this, clone the memory before hand.").printStackTrace();
++        }
++        return this.data;
++    }
++    Runnable cleaner;
++    public void cleanPooledBytes() {
++        Runnable cleaner = this.cleaner;
++        if (cleaner != null) { // This will only be possible for 2048 byte arrays
++            this.cleaner = null;
++            this.data = null;
++            cleaner.run();
++        }
++    }
++    /**
++     * Use ONLY if you know the life of your usage of the bytes matches the life of the nbt node itself.
++     * If this NBT node can go unreachable before your usage of the bytes is over with, DO NOT use this
++     */
++    public byte[] getBytesPoolSafe() {
++        // Paper end
+         return this.data;
+     }
+ 
+diff --git a/src/main/java/net/minecraft/server/NBTTagCompound.java b/src/main/java/net/minecraft/server/NBTTagCompound.java
+index 0000000000000000000000000000000000000000..0000000000000000000000000000000000000000 100644
+--- a/src/main/java/net/minecraft/server/NBTTagCompound.java
++++ b/src/main/java/net/minecraft/server/NBTTagCompound.java
+@@ -0,0 +0,0 @@ public class NBTTagCompound implements NBTBase {
+         return new byte[0];
+     }
+ 
++    // Paper start
++    public NBTTagByteArray getByteArrayTag(String s) {
++        try {
++            if (this.hasKeyOfType(s, 7)) {
++                return ((NBTTagByteArray) this.map.get(s));
++            }
++        } catch (ClassCastException classcastexception) {
++            throw new ReportedException(this.a(s, NBTTagByteArray.a, classcastexception));
++        }
++
++        return new NBTTagByteArray(new byte[0]);
++    }
++    // Paper end
++
+     public int[] getIntArray(String s) {
+         try {
+             if (this.hasKeyOfType(s, 11)) {
 diff --git a/src/main/java/net/minecraft/server/NibbleArray.java b/src/main/java/net/minecraft/server/NibbleArray.java
 index 0000000000000000000000000000000000000000..0000000000000000000000000000000000000000 100644
 --- a/src/main/java/net/minecraft/server/NibbleArray.java

scripts/applyPatches.sh

@@ -92,14 +92,14 @@ echo "Importing MC Dev"
 ./scripts/importmcdev.sh "$basedir" || exit 1
 
 # Apply paper
-cd "$basedir"
 (
     applyPatch "work/Spigot/Spigot-API" Paper-API HEAD &&
     applyPatch "work/Spigot/Spigot-Server" Paper-Server HEAD
+    cd "$basedir"
 
     # if we have previously ran ./paper mcdev, update it
     if [ -d "$workdir/Minecraft/$minecraftversion/src" ]; then
-        $basedir/scripts/makemcdevsrc.sh $basedir
+        ./scripts/makemcdevsrc.sh "$basedir"
     fi
 ) || (
     echo "Failed to apply Paper Patches"