Added FS record reader operator, module, test

2. incorporated review comments

library/src/main/java/org/apache/apex/malhar/lib/fs/FSRecordReader.java

@@ -0,0 +1,146 @@
+/**
+ * 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.apex.malhar.lib.fs;
+
+import java.io.IOException;
+import org.apache.hadoop.fs.FSDataInputStream;
+
+import com.datatorrent.api.Context.OperatorContext;
+import com.datatorrent.api.DefaultOutputPort;
+import com.datatorrent.lib.io.block.BlockMetadata;
+import com.datatorrent.lib.io.block.FSSliceReader;
+import com.datatorrent.lib.io.block.ReaderContext;
+
+/**
+ * This operator can be used for reading records/tuples from Filesystem in
+ * parallel (without ordering guarantees between tuples). Records can be
+ * delimited (e.g. newline) or fixed width records. Output tuples are byte[].
+ * 
+ * Typically, this operator will be connected to output of FileSplitterInput to
+ * read records in parallel.
+ */
+@org.apache.hadoop.classification.InterfaceStability.Evolving
+public class FSRecordReader extends FSSliceReader
+{
+  /**
+   * Record reader mode decides how to split the records.
+   */
+  public static enum RECORD_READER_MODE
+  {
+    DELIMITED_RECORD, FIXED_WIDTH_RECORD;
+  }
+
+  /**
+   * Criteria for record split
+   */
+  private RECORD_READER_MODE mode = RECORD_READER_MODE.DELIMITED_RECORD;
+
+  /**
+   * Length for fixed width record
+   */
+  private int recordLength;
+
+  /**
+   * Port to emit individual records/tuples as byte[]
+   */
+  public final transient DefaultOutputPort<byte[]> records = new DefaultOutputPort<byte[]>();
+
+  /**
+   * Initialize appropriate reader context based on mode selection
+   */
+  @Override
+  public void setup(OperatorContext context)
+  {
+    super.setup(context);
+    if (mode == RECORD_READER_MODE.FIXED_WIDTH_RECORD) {
+      ReaderContext.FixedBytesReaderContext<FSDataInputStream> fixedBytesReaderContext = new ReaderContext.FixedBytesReaderContext<FSDataInputStream>();
+      fixedBytesReaderContext.setLength(recordLength);
+      readerContext = fixedBytesReaderContext;
+    } else {
+      readerContext = new ReaderContext.ReadAheadLineReaderContext<FSDataInputStream>();
+    }
+  }
+
+  /**
+   * Read the block data and emit records based on reader context
+   *
+   * @param blockMetadata
+   *          block
+   * @throws IOException
+   */
+  protected void readBlock(BlockMetadata blockMetadata) throws IOException
+  {
+    readerContext.initialize(stream, blockMetadata, consecutiveBlock);
+    ReaderContext.Entity entity;
+    while ((entity = readerContext.next()) != null) {
+
+      counters.getCounter(ReaderCounterKeys.BYTES).add(entity.getUsedBytes());
+
+      byte[] record = entity.getRecord();
+
+      if (record != null) {
+        counters.getCounter(ReaderCounterKeys.RECORDS).increment();
+        records.emit(record);
+      }
+    }
+  }
+
+  /**
+   * Criteria for record split
+   * 
+   * @param mode
+   *          Mode
+   */
+  public void setMode(RECORD_READER_MODE mode)
+  {
+    this.mode = mode;
+  }
+
+  /**
+   * Criteria for record split
+   * 
+   * @return mode
+   */
+  public RECORD_READER_MODE getMode()
+  {
+    return mode;
+  }
+
+  /**
+   * Length for fixed width record
+   * 
+   * @param recordLength
+   */
+  public void setRecordLength(int recordLength)
+  {
+    this.recordLength = recordLength;
+  }
+
+  /**
+   * Length for fixed width record
+   * 
+   * @return record length
+   */
+  public int getRecordLength()
+  {
+    return recordLength;
+  }
+
+}