pregelix/pregelix-dataflow/src/main/java/edu/uci/ics/pregelix/dataflow/KeyValueParserFactory.java

/*
 * Copyright 2009-2013 by The Regents of the University of California
 * Licensed 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 from
 * 
 *     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 edu.uci.ics.pregelix.dataflow;

import java.io.DataOutput;
import java.nio.ByteBuffer;

import org.apache.hadoop.io.Writable;

import edu.uci.ics.hyracks.api.comm.IFrameWriter;
import edu.uci.ics.hyracks.api.context.IHyracksTaskContext;
import edu.uci.ics.hyracks.api.exceptions.HyracksDataException;
import edu.uci.ics.hyracks.dataflow.common.comm.io.ArrayTupleBuilder;
import edu.uci.ics.hyracks.dataflow.common.comm.io.FrameTupleAppender;
import edu.uci.ics.hyracks.dataflow.common.comm.util.FrameUtils;
import edu.uci.ics.hyracks.hdfs.api.IKeyValueParser;
import edu.uci.ics.hyracks.hdfs.api.IKeyValueParserFactory;

/**
 * @author yingyib
 */
public class KeyValueParserFactory<K extends Writable, V extends Writable> implements IKeyValueParserFactory<K, V> {
    private static final long serialVersionUID = 1L;

    @Override
    public IKeyValueParser<K, V> createKeyValueParser(IHyracksTaskContext ctx) throws HyracksDataException {
        final ArrayTupleBuilder tb = new ArrayTupleBuilder(2);
        final DataOutput dos = tb.getDataOutput();
        final ByteBuffer buffer = ctx.allocateFrame();
        final FrameTupleAppender appender = new FrameTupleAppender(ctx.getFrameSize());
        appender.reset(buffer, true);

        return new IKeyValueParser<K, V>() {

            @Override
            public void open(IFrameWriter writer) throws HyracksDataException {

            }

            @Override
            public void parse(K key, V value, IFrameWriter writer, String fileString) throws HyracksDataException {
                try {
                    tb.reset();
                    key.write(dos);
                    tb.addFieldEndOffset();
                    value.write(dos);
                    tb.addFieldEndOffset();
                    if (!appender.append(tb.getFieldEndOffsets(), tb.getByteArray(), 0, tb.getSize())) {
                        FrameUtils.flushFrame(buffer, writer);
                        appender.reset(buffer, true);
                        if (!appender.append(tb.getFieldEndOffsets(), tb.getByteArray(), 0, tb.getSize())) {
                            throw new HyracksDataException("tuple cannot be appended into the frame");
                        }
                    }
                } catch (Exception e) {
                    throw new HyracksDataException(e);
                }
            }

            @Override
            public void close(IFrameWriter writer) throws HyracksDataException {
                FrameUtils.flushFrame(buffer, writer);
            }

        };
    }
}