From fb24299a05050580981f4637328a697c341cc500 Mon Sep 17 00:00:00 2001
From: Mike Primm <mike@tabrasa.io>
Date: Sat, 11 May 2019 16:45:10 -0500
Subject: [PATCH] Improved workaround for 1.14 chunk load problems

---
 .../bukkit/helper/v114/MapChunkCache114.java  | 61 ++++++++++++++++++-
 1 file changed, 58 insertions(+), 3 deletions(-)

diff --git a/bukkit-helper-114/src/main/java/org/dynmap/bukkit/helper/v114/MapChunkCache114.java b/bukkit-helper-114/src/main/java/org/dynmap/bukkit/helper/v114/MapChunkCache114.java
index b58b97b8..9bc72a5e 100644
--- a/bukkit-helper-114/src/main/java/org/dynmap/bukkit/helper/v114/MapChunkCache114.java
+++ b/bukkit-helper-114/src/main/java/org/dynmap/bukkit/helper/v114/MapChunkCache114.java
@@ -1,6 +1,12 @@
 package org.dynmap.bukkit.helper.v114;
 
 import org.bukkit.block.Biome;
+
+import java.io.File;
+import java.io.IOException;
+import java.io.RandomAccessFile;
+import java.util.HashMap;
+
 import org.bukkit.ChunkSnapshot;
 import org.bukkit.World;
 import org.dynmap.bukkit.helper.AbstractMapChunkCache;
@@ -64,13 +70,14 @@ public class MapChunkCache114 extends AbstractMapChunkCache {
 	public Snapshot wrapChunkSnapshot(ChunkSnapshot css) {
 		return new WrappedSnapshot(css);
 	}
+	
 	@Override
     public boolean loadChunkNoGenerate(World w, int x, int z) {
 		boolean generated = true;
 		// Check one in each direction: see if all are generated
-		for (int xx = x-4; xx <= x+4; xx++) {
-			for (int zz = z-4; zz <= z+4; zz++) {
-				if (w.isChunkGenerated(xx, zz) == false) {
+		for (int xx = x-3; xx <= x+3; xx++) {
+			for (int zz = z-3; zz <= z+3; zz++) {
+				if (isChunkGenerated(w, xx, zz) == false) {
 					generated = false;
 					break;
 				}
@@ -82,4 +89,52 @@ public class MapChunkCache114 extends AbstractMapChunkCache {
 		}
 		return rslt;
     }
+	
+	private static class CacheRec {
+		long timestamp;
+		long[] blockmap; // ( bit = 1 at blockmap[z] & (1 << x))
+	}
+	private static HashMap<String, CacheRec> regioncache = new HashMap<String, CacheRec>();
+	private static long CACHE_TIMEOUT = 15000L;	// 15 second cache
+	
+	private static boolean isChunkGenerated(World w, int x, int z) {
+		String fn = String.format("%s/region/r.%d.%d.mca", w.getWorldFolder().getPath(), (x >> 5), (z >> 5));
+		CacheRec rec = regioncache.get(fn);
+		long ts = System.currentTimeMillis();
+		if ((rec == null) || (rec.timestamp < ts)) {
+			if (rec == null) { 
+				rec = new CacheRec();
+				rec.blockmap = new long[32];
+			}
+			rec.timestamp = ts + CACHE_TIMEOUT;
+			RandomAccessFile raf = null;
+			byte[] dat = new byte[4096];
+			try {
+				raf = new RandomAccessFile(fn, "r");
+				raf.seek(0);
+				raf.read(dat);
+			} catch (IOException iox) {
+			} finally {
+				if (raf != null) {
+					try {
+						raf.close();
+					} catch (IOException iox) {
+					}
+				}
+			}
+			// Build cache map
+			for (int zz = 0; zz < 32; zz++) {
+				long val = 0;
+				for (int xx = 0; xx < 32; xx++) {
+					int off = 4*((zz << 5) + xx);
+					int v = dat[off] | dat[off+1] | dat[off+2] | dat[off+3];
+					if (v != 0)
+						val |= (1L << xx);
+				}
+				rec.blockmap[zz] = val;
+			}
+			regioncache.put(fn, rec);
+		}
+		return (rec.blockmap[z & 31] & (1L << (x & 31))) != 0;
+	}
 }