Inspecting javaparser generator for bugs

core/src/main/java/com/github/gumtreediff/io/LineReader.java

@@ -54,10 +54,12 @@ public LineReader(Reader parent) {
     @Override
     public int read(char[] cbuf, int off, int len) throws IOException {
         int r = reader.read(cbuf, off, len);
-        for (int i = 0; i < len; i++)
-            if (cbuf[off + i] == '\n')
-                lines.add(currentPos + i);
-        currentPos += len;
+        if (r > 0) {
+            for (int i = 0; i < r; i++)
+                if (cbuf[off + i] == '\n')
+                    lines.add(currentPos + i);
+            currentPos += r;
+        }
         return r;
     }
 

core/src/test/java/com/github/gumtreediff/test/TestTreeIoUtils.java

@@ -90,6 +90,29 @@ public void testLineReader() throws IOException {
         assertArrayEquals(new int[] { 3, 2 }, lr.positionFor(9));
     }
 
+    @Test
+    public void testLineReaderWithPartialReads() throws IOException {
+        StringReader reader = new StringReader("foo\nbar\nbaz\n") {
+            @Override
+            public int read(char[] cbuf, int off, int len) throws IOException {
+                return super.read(cbuf, off, Math.min(len, 2));
+            }
+        };
+        LineReader lr = new LineReader(reader);
+        char[] buffer = new char[8];
+        StringBuilder contents = new StringBuilder();
+        int count;
+
+        while ((count = lr.read(buffer, 0, buffer.length)) != -1)
+            contents.append(buffer, 0, count);
+
+        assertEquals("foo\nbar\nbaz\n", contents.toString());
+        assertEquals(4, lr.positionFor(2, 1));
+        assertEquals(8, lr.positionFor(3, 1));
+        assertArrayEquals(new int[] { 2, 1 }, lr.positionFor(4));
+        assertArrayEquals(new int[] { 3, 1 }, lr.positionFor(8));
+    }
+
     @Test
     public void testPrintTextTree() throws Exception {
         TreeContext tc = getTreeContext();