/**
 * Copyright 2009 Saptarshi Guha
 *
 *   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 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.godhuli.rhipe;


import com.google.protobuf.InvalidProtocolBufferException;
import org.apache.commons.logging.Log;
import org.apache.commons.logging.LogFactory;
import org.apache.hadoop.mapreduce.Partitioner;
import org.godhuli.rhipe.REXPProtos.REXP;

public class RHPartitionerText extends Partitioner<RHBytesWritable, RHBytesWritable> {
    protected static final Log LOG = LogFactory.getLog(RHPartitionerText.class);

    public int getPartition(final RHBytesWritable key, final RHBytesWritable value, final int numReduceTasks) {
        int hashcode = 0;
        try {
            final REXP r = key.getParsed();
            for (int i = RHMRHelper.PARTITION_START; i <= RHMRHelper.PARTITION_END; i++) {
                // System.err.print( r.getStringValue(i).getStrval());
                final byte[] a = r.getStringValue(i).getStrval().getBytes();
                hashcode = hashCode(a, hashcode);
                // System.err.println(" hashcode="+hashcode);
            }
        }
        catch (InvalidProtocolBufferException e) {
            LOG.error(e);
        }
        return (hashcode & Integer.MAX_VALUE) % numReduceTasks;
    }

    protected int hashCode(final byte[] b, int currentHash) {
        for (int i = 0; i < b.length; i++) {
            currentHash = 31 * currentHash + b[i];
        }
        return currentHash;
    }

}