From 8375c097918c91e3a4ff945847903ff33c1f770f Mon Sep 17 00:00:00 2001
From: Aikar <aikar@aikar.co>
Date: Sat, 11 Aug 2018 00:49:20 -0400
Subject: [PATCH] Detect and repair corrupt Region Files

If the file has partial data written but not the full 8192 bytes,
then the server will be unable to load that region file...

I don't know why mojang only checks for 4096, when anything less than 8192 is a crash.

But to be safe, it will attempt to back up the file.

diff --git a/src/main/java/net/minecraft/server/RegionFile.java b/src/main/java/net/minecraft/server/RegionFile.java
index 5d2853b9ce..6a2edfd1e1 100644
--- a/src/main/java/net/minecraft/server/RegionFile.java
+++ b/src/main/java/net/minecraft/server/RegionFile.java
@@ -22,10 +22,10 @@ import javax.annotation.Nullable;
 
 public class RegionFile {
     private static final byte[] a = new byte[4096];
-    private final File b;
-    private RandomAccessFile c;
-    private final int[] d = new int[1024];
-    private final int[] e = new int[1024];
+    private final File b;private File getFile() { return b; } // Paper - OBFHELPER
+    private RandomAccessFile c;private RandomAccessFile getDataFile() { return c; } // Paper - OBFHELPER
+    private final int[] d = new int[1024];private int[] offsets = d; // Paper - OBFHELPER
+    private final int[] e = new int[1024];private int[] timestamps = e; // Paper - OBFHELPER
     private List<Boolean> f;
     private int g;
     private long h;
@@ -40,7 +40,7 @@ public class RegionFile {
             }
 
             this.c = new RandomAccessFile(file1, "rw");
-            if (this.c.length() < 4096L) {
+            if (this.c.length() < 8192L) { // Paper - headers should be 8192
                 this.c.write(a);
                 this.c.write(a);
                 this.g += 8192;
@@ -74,16 +74,16 @@ public class RegionFile {
             for(int j1 = 0; j1 < 1024; ++j1) {
                 int k = headerAsInts.get(); // Paper
                 this.d[j1] = k;
-                if (k != 0 && (k >> 8) + (k & 255) <= this.f.size()) {
+                if (k > 0 && (k >> 8) > 1 && (k >> 8) + (k & 255) <= this.f.size()) { // Paper >= 1 as 0/1 are the headers, and negative isnt valid
                     for(int l = 0; l < (k & 255); ++l) {
                         this.f.set((k >> 8) + l, false);
                     }
-                }
+                } else if (k != 0) deleteChunk(j1); // Paper
             }
 
             for(int k1 = 0; k1 < 1024; ++k1) {
                 int l1 = headerAsInts.get(); // Paper
-                this.e[k1] = l1;
+                if (offsets[k1] != 0) this.timestamps[k1] = l1; // Paper - don't set timestamp if it got 0'd above due to corruption
             }
         } catch (IOException ioexception) {
             ioexception.printStackTrace();
@@ -276,6 +276,55 @@ public class RegionFile {
 
     }
 
+    // Paper start
+    public synchronized void deleteChunk(int j1) {
+        backup();
+        int k = offsets[j1];
+        int x = j1 & 1024;
+        int z = j1 >> 2;
+        int offset = (k >> 8);
+        int len = (k & 255);
+        org.apache.logging.log4j.Logger logger = org.apache.logging.log4j.LogManager.getLogger();
+        String debug = "idx:" + + j1 + " - " + x + "," + z + " - offset: " + offset + " - len: " + len;
+        try {
+            RandomAccessFile file = getDataFile();
+            file.seek(j1 * 4);
+            file.writeInt(0);
+            // clear the timestamp
+            file.seek(4096 + j1 * 4);
+            file.writeInt(0);
+            timestamps[j1] = 0;
+            offsets[j1] = 0;
+            logger.error("Deleted corrupt chunk (" + debug + ") " + getFile().getAbsolutePath(), e);
+        } catch (IOException e) {
+
+            logger.error("Error deleting corrupt chunk (" + debug + ") " + getFile().getAbsolutePath(), e);
+        }
+    }
+    private boolean backedUp = false;
+    private synchronized void backup() {
+        if (backedUp) {
+            return;
+        }
+        backedUp = true;
+        File file = this.getFile();
+        java.text.DateFormat formatter = new java.text.SimpleDateFormat("yyyy-MM-dd");
+        java.util.Date today = new java.util.Date();
+        File corrupt = new File(file.getParentFile(), file.getName() + "." + formatter.format(today) + ".corrupt");
+        if (corrupt.exists()) {
+            return;
+        }
+        org.apache.logging.log4j.Logger logger = org.apache.logging.log4j.LogManager.getLogger();
+        logger.error("Region file " + file.getAbsolutePath() + " was corrupt. Backing up to " + corrupt.getAbsolutePath() + " and repairing");
+        try {
+            java.nio.file.Files.copy(file.toPath(), corrupt.toPath());
+
+        } catch (IOException e) {
+            logger.error("Error backing up corrupt file" + file.getAbsolutePath(), e);
+        }
+    }
+    // Paper end
+
     class ChunkBuffer extends ByteArrayOutputStream {
         private final int b;
         private final int c;
-- 
2.19.1