HADOOP-6497. Add an adapter for Avro's SeekableInput interface, so that Avro can read FileSystem data. Contributed by Aaron Kimball.

git-svn-id: https://svn.apache.org/repos/asf/hadoop/common/trunk@900607 13f79535-47bb-0310-9956-ffa450edef68

CHANGES.txt

@@ -104,6 +104,10 @@ Trunk (unreleased changes)
     HADOOP-6492. Make some Avro serialization APIs public.
     (Aaron Kimball via cutting)
 
+    HADOOP-6497. Add an adapter for Avro's SeekableInput interface, so
+    that Avro can read FileSystem data.
+    (Aaron Kimball via cutting)
+
   OPTIMIZATIONS
 
   BUG FIXES

src/java/org/apache/hadoop/fs/AvroFSInput.java

@@ -0,0 +1,63 @@
+/**
+ * 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.hadoop.fs;
+
+import java.io.Closeable;
+import java.io.IOException;
+
+import org.apache.avro.file.SeekableInput;
+
+/** Adapts an {@link FSDataInputStream} to Avro's SeekableInput interface. */
+public class AvroFSInput implements Closeable, SeekableInput {
+  private final FSDataInputStream stream;
+  private final long len;
+
+  /** Construct given an {@link FSDataInputStream} and its length. */
+  public AvroFSInput(final FSDataInputStream in, final long len) {
+    this.stream = in;
+    this.len = len;
+  }
+
+  /** Construct given a {@link FileContext} and a {@link Path}. */
+  public AvroFSInput(final FileContext fc, final Path p) throws IOException {
+    FileStatus status = fc.getFileStatus(p);
+    this.len = status.getLen();
+    this.stream = fc.open(p);
+  }
+
+  public long length() {
+    return len;
+  }
+
+  public int read(byte[] b, int off, int len) throws IOException {
+    return stream.read(b, off, len);
+  }
+
+  public void seek(long p) throws IOException {
+    stream.seek(p);
+  }
+
+  public long tell() throws IOException {
+    return stream.getPos();
+  }
+
+  public void close() throws IOException {
+    stream.close();
+  }
+}

src/test/core/org/apache/hadoop/fs/TestAvroFSInput.java

@@ -0,0 +1,88 @@
+/**
+ * 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.hadoop.fs;
+
+import java.io.BufferedWriter;
+import java.io.IOException;
+import java.io.OutputStreamWriter;
+
+import org.apache.hadoop.conf.Configuration;
+
+import junit.framework.TestCase;
+
+public class TestAvroFSInput extends TestCase {
+
+  private static final String INPUT_DIR = "AvroFSInput";
+
+  private Path getInputPath() {
+    String dataDir = System.getProperty("test.build.data");
+    if (null == dataDir) {
+      return new Path(INPUT_DIR);
+    } else {
+      return new Path(new Path(dataDir), INPUT_DIR);
+    }
+  }
+
+
+  public void testAFSInput() throws Exception {
+    Configuration conf = new Configuration();
+    FileSystem fs = FileSystem.getLocal(conf);
+
+    Path dir = getInputPath();
+
+    if (!fs.exists(dir)) {
+      fs.mkdirs(dir);
+    }
+
+    Path filePath = new Path(dir, "foo");
+    if (fs.exists(filePath)) {
+      fs.delete(filePath, false);
+    }
+
+    FSDataOutputStream ostream = fs.create(filePath);
+    BufferedWriter w = new BufferedWriter(new OutputStreamWriter(ostream));
+    w.write("0123456789");
+    w.close();
+
+    // Create the stream
+    FileContext fc = FileContext.getFileContext(conf);
+    AvroFSInput avroFSIn = new AvroFSInput(fc, filePath);
+
+    assertEquals(10, avroFSIn.length());
+
+    // Check initial position
+    byte [] buf = new byte[1];
+    assertEquals(0, avroFSIn.tell());
+
+    // Check a read from that position.
+    avroFSIn.read(buf, 0, 1);
+    assertEquals(1, avroFSIn.tell());
+    assertEquals('0', (char)buf[0]);
+
+    // Check a seek + read
+    avroFSIn.seek(4);
+    assertEquals(4, avroFSIn.tell());
+    avroFSIn.read(buf, 0, 1);
+    assertEquals('4', (char)buf[0]);
+    assertEquals(5, avroFSIn.tell());
+
+    avroFSIn.close();
+  }
+}
+