Github user vanzin commented on a diff in the pull request:
https://github.com/apache/spark/pull/5400#discussion_r31545767
--- Diff:
network/common/src/test/java/org/apache/spark/network/buffer/LargeByteBufferHelperSuite.java
---
@@ -0,0 +1,84 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one or more
+ * contributor license agreements. See the NOTICE file distributed with
+ * this work for additional information regarding copyright ownership.
+ * The ASF licenses this file to You under the Apache License, Version 2.0
+ * (the "License"); you may not use this file except in compliance with
+ * the License. You may obtain a copy of the License at
+ *
+ * http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+package org.apache.spark.network.buffer;
+
+import java.io.*;
+import java.nio.channels.FileChannel;
+
+import org.junit.Test;
+
+import static org.junit.Assert.*;
+
+public class LargeByteBufferHelperSuite {
+
+ @Test
+ public void testMapFile() throws IOException {
+ File testFile = File.createTempFile("large-byte-buffer-test", ".bin");
+ try {
+ testFile.deleteOnExit();
+ OutputStream out = new FileOutputStream(testFile);
+ byte[] buffer = new byte[1 << 16];
+ long len = ((long)buffer.length) + Integer.MAX_VALUE + 1;
+ for (int i = 0; i < buffer.length; i++) {
+ buffer[i] = (byte) i;
+ }
+ for (int i = 0; i < len / buffer.length; i++) {
+ out.write(buffer);
--- End diff --
I'm a little concerned that writing the same data over and over might mask
some nasty issues like the one I think I found earlier. Perhaps this should be
writing random data instead? (That would probably be prohibitively slow with
such a large test file, though.)
You could have two `java.util.Random` instances with the same seed to be
able to recreate the input data while checking.
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