    001/*
    002 * Copyright (c) 2007-2016 Concurrent, Inc. All Rights Reserved.
    003 *
    004 * Project and contact information: http://www.cascading.org/
    005 *
    006 * This file is part of the Cascading project.
    007 *
    008 * Licensed under the Apache License, Version 2.0 (the "License");
    009 * you may not use this file except in compliance with the License.
    010 * You may obtain a copy of the License at
    011 *
    012 *     http://www.apache.org/licenses/LICENSE-2.0
    013 *
    014 * Unless required by applicable law or agreed to in writing, software
    015 * distributed under the License is distributed on an "AS IS" BASIS,
    016 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
    017 * See the License for the specific language governing permissions and
    018 * limitations under the License.
    019 */
    020
    021package cascading.tuple.hadoop.util;
    022
    023import java.io.Serializable;
    024import java.util.Arrays;
    025import java.util.Comparator;
    026
    027import cascading.tuple.Hasher;
    028import cascading.tuple.StreamComparator;
    029import cascading.tuple.hadoop.io.BufferedInputStream;
    030import org.apache.hadoop.io.WritableComparator;
    031
    032/**
    033 * Class BytesComparator is used to compare arrays of bytes.
    034 * <p/>
    035 * Note that BytesComparator implements {@link Hasher}, but for the Hasher interface to be applied during grouping,
    036 * sorting or joining, it must be set on a {@link cascading.tuple.Fields} instance via
    037 * {@link cascading.tuple.Fields#setComparator(Comparable, java.util.Comparator)}.
    038 */
    039public class BytesComparator implements StreamComparator<BufferedInputStream>, Hasher<byte[]>, Comparator<byte[]>, Serializable
    040  {
    041  @Override
    042  public int compare( byte[] lhs, byte[] rhs )
    043    {
    044    if( lhs == rhs )
    045      return 0;
    046
    047    return WritableComparator.compareBytes( lhs, 0, lhs.length, rhs, 0, rhs.length );
    048    }
    049
    050  @Override
    051  public int compare( BufferedInputStream lhsStream, BufferedInputStream rhsStream )
    052    {
    053    byte[] lhs = lhsStream.getBuffer();
    054    int lhsPos = lhsStream.getPosition();
    055    int lhsLen = readLen( lhs, lhsPos );
    056
    057    lhsStream.skip( lhsLen + 4 );
    058
    059    byte[] rhs = rhsStream.getBuffer();
    060    int rhsPos = rhsStream.getPosition();
    061    int rhsLen = readLen( rhs, rhsPos );
    062
    063    rhsStream.skip( rhsLen + 4 );
    064
    065    return WritableComparator.compareBytes( lhs, lhsPos + 4, lhsLen, rhs, rhsPos + 4, rhsLen );
    066    }
    067
    068  private int readLen( byte[] buffer, int off )
    069    {
    070    return ( ( buffer[ off ] & 0xff ) << 24 ) +
    071      ( ( buffer[ off + 1 ] & 0xff ) << 16 ) +
    072      ( ( buffer[ off + 2 ] & 0xff ) << 8 ) +
    073      ( buffer[ off + 3 ] & 0xff );
    074    }
    075
    076  @Override
    077  public int hashCode( byte[] value )
    078    {
    079    return Arrays.hashCode( value );
    080    }
    081  }