prefixmap.java

MG4J (Managing Gigabytes for Java) is a free full-text search engine for large document collections

package it.unimi.dsi.mg4j.index;

import it.unimi.dsi.mg4j.search.Interval;
import it.unimi.dsi.mg4j.util.MutableString;

/*		 
 * MG4J: Managing Gigabytes for Java
 *
 * Copyright (C) 2004-2007 Sebastiano Vigna 
 *
 *  This library is free software; you can redistribute it and/or modify it
 *  under the terms of the GNU Lesser General Public License as published by the Free
 *  Software Foundation; either version 2.1 of the License, or (at your option)
 *  any later version.
 *
 *  This library 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 Lesser General Public License
 *  for more details.
 *
 *  You should have received a copy of the GNU Lesser 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.
 *
 */


/** A map from prefixes to term intervals (and possibly viceversa).
 *
 * <P>Given a list of terms in lexicographic order numbered from 0, we can ask, given a prefix,
 * which interval of terms starts with the given prefix. This information is very useful to 
 * satisfy prefix queries (e.g., <samp>monitor*</samp>) with a brute-force approach, that is,
 * {@linkplain it.unimi.dsi.mg4j.search.OrDocumentIterator or-ing the document iterators} corresponding
 * to each term. The interval is more useful than the actual list of terms starting with the prefix,
 * as it allows to build directly the composed iterator.
 * 
 * <P>Optionally, a prefix map may provide the opposite service: given an interval of terms, it
 *  may provide the maximum common prefix. This feature can be checked for by calling {@link #hasPrefixes()}.
 *
 * @author Sebastiano Vigna 
 * @since 0.9.2
 * @deprecated As of MG4J 2.1, replaced by {@link it.unimi.dsi.util.PrefixMap}.
 */

@Deprecated
public interface PrefixMap {
	/** Returns the interval of terms starting with the given prefix.
	 * 
	 * @param prefix a prefix.
	 * @return the interval of terms starting with <code>prefix</code> 
	 * ({@link it.unimi.dsi.mg4j.search.Intervals#EMPTY_INTERVAL} in case no term starts with <code>prefix</code>).
	 */

	public Interval getInterval( CharSequence prefix );

	/** Returns true if this prefix map supports {@linkplain #getPrefix(Interval) prefix retrieval}. 
	 * 
	 * @return true if this prefix map supports {@linkplain #getPrefix(Interval) prefix retrieval}.
	 */
	
	public boolean hasPrefixes();
	
	/** Returns the maximum prefix common to all terms in the given nonempty interval (optional operation).
	 * 
	 * @param interval an interval.
	 * @return the maximum prefix common to all terms in the given nonempty interval.
	 */

	public CharSequence getPrefix( Interval interval );

	/** Writes in the given mutable string the maximum prefix common to all terms in the given nonempty interval (optional operation).
	 * 
	 * @param interval an interval.
	 * @param prefix a mutable string that will be filled with the maximum prefix common to all terms in the given nonempty interval.
	 * @return <code>prefix</code>.
	 */

	public MutableString getPrefix( Interval interval, MutableString prefix );

	/** Returns the number of terms in this prefix map. 
	 * @return the number of terms in this prefix map.
	 */
	public int size();
}