Add test for FileChannels.contentEquals() #509

- Fix FileChannels.contentEquals()

Author: garydgregory

src/changes/changes.xml

@@ -50,6 +50,8 @@ The <action> type attribute can be add,update,fix,remove.
     <release version="2.15.1" date="20YY-MM-DD" description="Java 8 is required.">
       <!-- FIX -->
       <action dev="sebb" type="fix" due-to="Gregor Dschung">Fix wrong issue id in changelog #503.</action>
+      <action dev="ggregory" type="fix" due-to="Stephan Markwalder, Gary Gregory">Add test for FileChannels.contentEquals() #509.</action>
+      <action dev="ggregory" type="fix" due-to="Gary Gregory">Fix FileChannels.contentEquals().</action>
     </release>
     <release version="2.15.0" date="2023-10-21" description="Java 8 is required.">
       <!-- FIX -->

src/main/java/org/apache/commons/io/channels/FileChannels.java

@@ -60,6 +60,8 @@ public static boolean contentEquals(final FileChannel channel1, final FileChanne
         while (true) {
             final int read1 = channel1.read(byteBuffer1);
             final int read2 = channel2.read(byteBuffer2);
+            byteBuffer1.clear();
+            byteBuffer2.clear();
             if (read1 == IOUtils.EOF && read2 == IOUtils.EOF) {
                 return byteBuffer1.equals(byteBuffer2);
             }
@@ -69,8 +71,6 @@ public static boolean contentEquals(final FileChannel channel1, final FileChanne
             if (!byteBuffer1.equals(byteBuffer2)) {
                 return false;
             }
-            byteBuffer1.clear();
-            byteBuffer2.clear();
         }
     }
 

src/test/java/org/apache/commons/io/channels/FileChannelsTest.java

@@ -0,0 +1,112 @@
+/*
+ * 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.commons.io.channels;
+
+import static java.nio.charset.StandardCharsets.US_ASCII;
+import static org.junit.jupiter.api.Assertions.assertFalse;
+import static org.junit.jupiter.api.Assertions.assertNotEquals;
+import static org.junit.jupiter.api.Assertions.assertTrue;
+
+import java.io.File;
+import java.io.FileInputStream;
+import java.io.IOException;
+import java.nio.channels.FileChannel;
+
+import org.apache.commons.io.FileUtils;
+import org.apache.commons.io.file.AbstractTempDirTest;
+import org.apache.commons.lang3.StringUtils;
+import org.junit.jupiter.api.Test;
+
+/**
+ * Tests {@link FileChannels}.
+ */
+public class FileChannelsTest extends AbstractTempDirTest {
+
+    private static final int BUFFER_SIZE = 1024;
+    private static final String CONTENT = StringUtils.repeat("x", BUFFER_SIZE);
+
+    private boolean isEmpty(final File empty) {
+        return empty.length() == 0;
+    }
+
+    private void testContentEquals(final String content1, final String content2) throws IOException {
+        assertTrue(FileChannels.contentEquals(null, null, BUFFER_SIZE));
+
+        // Prepare test files with same size but different content
+        // (first 3 bytes are different, followed by a large amount of equal content)
+        final File file1 = new File(tempDirFile, "test1.txt");
+        final File file2 = new File(tempDirFile, "test2.txt");
+        FileUtils.writeStringToFile(file1, content1, US_ASCII);
+        FileUtils.writeStringToFile(file2, content2, US_ASCII);
+
+        // File checksums are different
+        assertNotEquals(FileUtils.checksumCRC32(file1), FileUtils.checksumCRC32(file2));
+
+        try (FileInputStream stream1 = new FileInputStream(file1);
+                FileInputStream stream2 = new FileInputStream(file2);
+                FileChannel channel1 = stream1.getChannel();
+                FileChannel channel2 = stream2.getChannel()) {
+            assertFalse(FileChannels.contentEquals(channel1, channel2, BUFFER_SIZE));
+        }
+        try (FileInputStream stream1 = new FileInputStream(file1);
+                FileInputStream stream2 = new FileInputStream(file2);
+                FileChannel channel1 = stream1.getChannel();
+                FileChannel channel2 = stream2.getChannel()) {
+            assertTrue(FileChannels.contentEquals(channel1, channel1, BUFFER_SIZE));
+            assertTrue(FileChannels.contentEquals(channel2, channel2, BUFFER_SIZE));
+        }
+    }
+
+    @Test
+    public void testContentEqualsDifferentPostfix() throws IOException {
+        testContentEquals(CONTENT + "ABC", CONTENT + "XYZ");
+    }
+
+    @Test
+    public void testContentEqualsDifferentPrefix() throws IOException {
+        testContentEquals("ABC" + CONTENT, "XYZ" + CONTENT);
+    }
+
+    @Test
+    public void testContentEqualsEmpty() throws IOException {
+        assertTrue(FileChannels.contentEquals(null, null, BUFFER_SIZE));
+
+        final File empty = new File(tempDirFile, "empty.txt");
+        final File notEmpty = new File(tempDirFile, "not-empty.txt");
+        FileUtils.writeStringToFile(empty, StringUtils.EMPTY, US_ASCII);
+        FileUtils.writeStringToFile(notEmpty, "X", US_ASCII);
+        assertTrue(isEmpty(empty));
+        assertFalse(isEmpty(notEmpty));
+
+        // File checksums are different
+        assertNotEquals(FileUtils.checksumCRC32(empty), FileUtils.checksumCRC32(notEmpty));
+
+        try (FileInputStream streamEmpty = new FileInputStream(empty);
+                FileInputStream streamNotEmpty = new FileInputStream(notEmpty);
+                FileChannel channelEmpty = streamEmpty.getChannel();
+                FileChannel channelNotEmpty = streamNotEmpty.getChannel()) {
+            assertFalse(FileChannels.contentEquals(channelEmpty, channelNotEmpty, BUFFER_SIZE));
+            assertFalse(FileChannels.contentEquals(null, channelNotEmpty, BUFFER_SIZE));
+            assertFalse(FileChannels.contentEquals(channelNotEmpty, null, BUFFER_SIZE));
+            assertTrue(FileChannels.contentEquals(channelEmpty, channelEmpty, BUFFER_SIZE));
+            assertTrue(FileChannels.contentEquals(null, channelEmpty, BUFFER_SIZE));
+            assertTrue(FileChannels.contentEquals(channelEmpty, null, BUFFER_SIZE));
+            assertTrue(FileChannels.contentEquals(channelNotEmpty, channelNotEmpty, BUFFER_SIZE));
+        }
+    }
+
+}