package it.unimi.dsi.util;
/*
* Sux4J: Succinct data structures for Java
*
* Copyright (C) 2009 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.
*
*/
import it.unimi.dsi.Util;
import it.unimi.dsi.fastutil.io.BinIO;
import it.unimi.dsi.fastutil.objects.AbstractObject2LongFunction;
import it.unimi.dsi.fastutil.objects.Object2LongFunction;
import it.unimi.dsi.fastutil.objects.ObjectList;
import it.unimi.dsi.io.FileLinesCollection;
import it.unimi.dsi.lang.MutableString;
import java.io.IOException;
import java.io.Serializable;
import java.nio.charset.Charset;
import org.apache.log4j.Logger;
import com.martiansoftware.jsap.FlaggedOption;
import com.martiansoftware.jsap.JSAP;
import com.martiansoftware.jsap.JSAPException;
import com.martiansoftware.jsap.JSAPResult;
import com.martiansoftware.jsap.Parameter;
import com.martiansoftware.jsap.SimpleJSAP;
import com.martiansoftware.jsap.Switch;
import com.martiansoftware.jsap.UnflaggedOption;
import com.martiansoftware.jsap.stringparsers.ForNameStringParser;
/** A string map based on a function signed using the original list of strings.
*
* <p>A minimal perfect hash function maps a set of string to an initial segment of the natural
* numbers, but will actually map <em>any</em> string to that segment. We can check that
* a string is part of the key set by hashing it to a value <var>h</var>, and checking that the <var>h</var>-th
* string of the original list does coincide. Since, moreover, this class implements {@link StringMap},
* and thus {@linkplain #list() exposes the original list}, we have a two-way
* dictionary. In other words, this is a <em>full</em> {@link StringMap} implementation.
*
* <p>Note that some care must be exercised: {@link CharSequence}'s contract does not
* prescribe equality by content, so if your function behaves badly on some implementations of
* {@link CharSequence} you might make the checks fail. To avoid difficulties, the
* constructor checks that every string in the list is hashed correctly.
*
* <p>For the same reason, this class implements <code>StringMap<MutableString></code>, and
* requires that the list of strings provided at construction time is actually a list of
* {@linkplain MutableString mutable strings}.
*
* <p>A typical usage of this class pairs a {@link FrontCodedStringList} with some kind
* of succinct structure from <a href="http://sux4j.dsi.unimi.it/">Sux4J</a>.
*
* @author Sebastiano Vigna
* @since 1.0.8
*/
public class LiterallySignedStringMap extends AbstractObject2LongFunction<CharSequence> implements StringMap<MutableString>, Serializable {
private static final long serialVersionUID = 0L;
private static final Logger LOGGER = Util.getLogger( LiterallySignedStringMap.class );
/** The underlying map. */
protected final Object2LongFunction<? extends CharSequence> function;
/** The underlying list. */
protected final ObjectList<? extends MutableString> list;
/** The size of {@link #list}. */
protected final int size;
/** Creates a new shift-add-xor signed string map using a given hash map.
*
* @param function a function mapping each string in <code>list</code> to its ordinal position.
* @param list a list of strings.
*/
public LiterallySignedStringMap( final Object2LongFunction<? extends CharSequence> function, final ObjectList<? extends MutableString> list ) {
this.function = function;
this.list = list;
size = list.size();
for( int i = 0; i < size; i++ ) if ( function.getLong( list.get( i ) ) != i ) throw new IllegalArgumentException( "Function and list do not agree" );
defRetValue = -1;
}
@SuppressWarnings("unchecked")
public long getLong( final Object o ) {
final CharSequence s = (CharSequence)o;
final long index = function.getLong( s );
return index >= 0 && index < size && list.get( (int)index ).equals( s ) ? index : defRetValue;
}
@SuppressWarnings("unchecked")
public Long get( final Object o ) {
final CharSequence s = (CharSequence)o;
final long index = function.getLong( s );
return index >= 0 && index < size && list.get( (int)index ).equals( s ) ? Long.valueOf( index ) : null;
}
public int size() {
return function.size();
}
public boolean containsKey( final Object o ) {
return getLong( o ) != -1;
}
public ObjectList<? extends MutableString> list() {
return list;
}
@SuppressWarnings("unchecked")
public static void main( final String[] arg ) throws IOException, JSAPException, ClassNotFoundException, SecurityException, NoSuchMethodException {
final SimpleJSAP jsap = new SimpleJSAP( LiterallySignedStringMap.class.getName(), "Builds a shift-add-xor signed string map by reading a newline-separated list of strings and a function built on the same list of strings.",
new Parameter[] {
new FlaggedOption( "encoding", ForNameStringParser.getParser( Charset.class ), "UTF-8", JSAP.NOT_REQUIRED, 'e', "encoding", "The string file encoding." ),
new Switch( "zipped", 'z', "zipped", "The string list is compressed in gzip format." ),
new Switch( "text", 't', "text", "The string list actually a text file, with one string per line." ),
new UnflaggedOption( "function", JSAP.STRING_PARSER, JSAP.NO_DEFAULT, JSAP.REQUIRED, JSAP.NOT_GREEDY, "The filename of the function to be signed." ),
new UnflaggedOption( "list", JSAP.STRING_PARSER, JSAP.NO_DEFAULT, JSAP.REQUIRED, JSAP.NOT_GREEDY, "The filename of the serialised list of strings, or of a text file containing a list of strings, if -t is specified." ),
new UnflaggedOption( "map", JSAP.STRING_PARSER, JSAP.NO_DEFAULT, JSAP.REQUIRED, JSAP.NOT_GREEDY, "The filename of the resulting map." ),
});
JSAPResult jsapResult = jsap.parse( arg );
if ( jsap.messagePrinted() ) return;
final String functionName = jsapResult.getString( "function" );
final String listName = jsapResult.getString( "list" );
final String mapName = jsapResult.getString( "map" );
final Charset encoding = (Charset)jsapResult.getObject( "encoding" );
final boolean zipped = jsapResult.getBoolean( "zipped" );
final boolean text = jsapResult.getBoolean( "text" );
ObjectList<MutableString> list = text ? new FileLinesCollection( listName, encoding.toString(), zipped ).allLines() : (ObjectList)BinIO.loadObject( listName );
LOGGER.info( "Signing..." );
BinIO.storeObject( new LiterallySignedStringMap( (Object2LongFunction)BinIO.loadObject( functionName ), list ), mapName );
LOGGER.info( "Completed." );
}
}