From 60c113b0e85eab82e0803834af2dd2837d681e73 Mon Sep 17 00:00:00 2001
From: Daniel Mills <danielmillst@gmail.com>
Date: Tue, 20 Jul 2021 02:58:11 -0400
Subject: [PATCH] Allow reading region chunks without loading mca

---
 .../volmit/iris/engine/data/mca/MCAFile.java  | 24 +++++++++++++++++++
 .../volmit/iris/engine/data/mca/MCAUtil.java  | 10 ++++++++
 2 files changed, 34 insertions(+)

diff --git a/src/main/java/com/volmit/iris/engine/data/mca/MCAFile.java b/src/main/java/com/volmit/iris/engine/data/mca/MCAFile.java
index 86b04fe1b..ca4842971 100644
--- a/src/main/java/com/volmit/iris/engine/data/mca/MCAFile.java
+++ b/src/main/java/com/volmit/iris/engine/data/mca/MCAFile.java
@@ -19,6 +19,9 @@
 package com.volmit.iris.engine.data.mca;
 
 import com.volmit.iris.engine.data.nbt.tag.CompoundTag;
+import com.volmit.iris.engine.hunk.storage.ArrayHunk;
+import com.volmit.iris.util.collection.KList;
+import com.volmit.iris.util.math.Position2;
 
 import java.io.IOException;
 import java.io.RandomAccessFile;
@@ -88,6 +91,27 @@ public class MCAFile {
         }
     }
 
+    public KList<Position2> samplePositions(RandomAccessFile raf) throws IOException {
+        KList<Position2> p2 = new KList<>();
+        chunks = new AtomicReferenceArray<>(1024);
+        int x = 0;
+        int z = 0;
+        for (int i = 0; i < 1024; i++) {
+            x++;
+            z++;
+
+            raf.seek(i * 4);
+            int offset = raf.read() << 16;
+            offset |= (raf.read() & 0xFF) << 8;
+            offset |= raf.read() & 0xFF;
+            if (raf.readByte() == 0) {
+                continue;
+            }
+            p2.add(new Position2(x & 31, (z / 32) & 31));
+        }
+        return p2;
+    }
+
     public AtomicReferenceArray<Chunk> getChunks() {
         return chunks;
     }
diff --git a/src/main/java/com/volmit/iris/engine/data/mca/MCAUtil.java b/src/main/java/com/volmit/iris/engine/data/mca/MCAUtil.java
index e438cae10..68a23e4b8 100644
--- a/src/main/java/com/volmit/iris/engine/data/mca/MCAUtil.java
+++ b/src/main/java/com/volmit/iris/engine/data/mca/MCAUtil.java
@@ -18,6 +18,9 @@
 
 package com.volmit.iris.engine.data.mca;
 
+import com.volmit.iris.util.collection.KList;
+import com.volmit.iris.util.math.Position2;
+
 import java.io.File;
 import java.io.IOException;
 import java.io.RandomAccessFile;
@@ -83,6 +86,13 @@ public final class MCAUtil {
         }
     }
 
+    public static KList<Position2> sampleChunkPositions(File file) throws IOException {
+        MCAFile mcaFile = newMCAFile(file);
+        try (RandomAccessFile raf = new RandomAccessFile(file, "r")) {
+            return mcaFile.samplePositions(raf);
+        }
+    }
+
     /**
      * Calls {@link MCAUtil#write(MCAFile, File, boolean)} without changing the timestamps.
      *