OAK-11977 Tree store: BufferOverflowException (#2571)

Author: thomasmueller

oak-run-commons/src/main/java/org/apache/jackrabbit/oak/index/indexer/document/tree/store/PageFile.java

@@ -110,8 +110,10 @@ public byte[] toBytes() {
         // synchronization is needed because we share the buffer
         synchronized (PageFile.class) {
             ByteBuffer buff = REUSED_BUFFER;
-            if (buff.capacity() < sizeInBytes * 2) {
-                buff = REUSED_BUFFER = ByteBuffer.allocate(sizeInBytes * 2);
+            // the sizeInBytes only assumes 1 byte per character
+            // but there can be more byte due to using UTF-8
+            if (buff.capacity() < sizeInBytes * 4) {
+                buff = REUSED_BUFFER = ByteBuffer.allocate(sizeInBytes * 4);
             }
             buff.rewind();
             // first byte may not be '4', as that is used for LZ4 compression

oak-run-commons/src/test/java/org/apache/jackrabbit/oak/index/indexer/document/tree/store/PageFileTest.java

@@ -61,4 +61,16 @@ public void serializeInnerNode() {
         assertEquals(f.getUpdate(), f2.getUpdate());
     }
 
+    @Test
+    public void largeStringTest() {
+        PageFile f = new PageFile(false, 1_000_000);
+        StringBuilder buff = new StringBuilder();
+        for (int i = 0; i < 1_000_000; i++) {
+            buff.append('\uffff');
+        }
+        f.appendRecord("test", buff.toString());
+        // expected that the buffer doesn't overflow here
+        f.toBytes();
+    }
+
 }