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/**

Copyright (C) SYSTAP, LLC DBA Blazegraph 2006-2016.  All rights reserved.

Contact:
     SYSTAP, LLC DBA Blazegraph
     2501 Calvert ST NW #106
     Washington, DC 20008
     [email protected]

This program is free software; you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation; version 2 of the License.

This program is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
GNU General Public License for more details.

You should have received a copy of the GNU General Public License
along with this program; if not, write to the Free Software
Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
*/
package com.bigdata.btree.raba;

import java.util.Iterator;

/**
 * Class with implementations supporting mutable and immutable variable length
 * byte[] keys.
 * 
 * @todo supporting a scalar int32 key natively would provide better performance
 *       for an object index. once it is up to int64, the byte[] approach could
 *       in fact be better on 32-bit hardware.
 * 
 * @todo explore the use of sparse buffers that minimize copying for more
 *       efficient management of large #s of keys - how would search work for
 *       such buffers?
 * 
 * @todo explore use of interpolated search. certainly we should be able to
 *       estimate the distribution of the keys when creating an immutable key
 *       buffer and choose binary vs interpolated vs linear search based on
 *       that.
 * 
 * @author Bryan Thompson
 * @version $Id$
 */
public abstract class AbstractKeyBuffer implements IRaba {

    /**
     * Test the search key against the leading prefix shared by all bytes in the
     * key buffer.
     * 
     * @param prefixLength
     *            The length of the prefix shared by all keys in the buffer.
     * 
     * @param searchKey
     *            The search key.
     * 
     * @return Zero iff all bytes match and otherwise the insert position for
     *         the search key in the buffer. The insert position will be before
     *         the first key iff the search key is less than the prefix (-1) and
     *         will be after the last key iff the search key is greater than the
     *         prefix (-(nkeys)-1).
     */
    abstract protected int _prefixMatchLength(final int prefixLength,
            final byte[] searchKey);
    
    /**
     * Linear search.
     */
    abstract protected int _linearSearch(final int searchKeyOffset, final byte[] searchKey);

    /**
     * Binary search.
     */
    abstract protected int _binarySearch(final int searchKeyOffset, final byte[] searchKey);

    @Override
    public Iterator iterator() {

        return new Iterator() {

            int i = 0;
            
            @Override
            public boolean hasNext() {
                return i < size();
            }

            @Override
            public byte[] next() {
                return get(i++);
            }

            @Override
            public void remove() {
                throw new UnsupportedOperationException();
            }
            
        };

    }

    /**
     * Return the largest leading prefix shared by all keys.
     */
    abstract public byte[] getPrefix();
    
    /**
     * The length of the leading prefix shared by all keys.
     */
    abstract public int getPrefixLength();

}