package de.spieleck.app.cngram ;

/*	Please see the license information in the header below. */

/*
 NGramJ - n-gram based text classification
 Copyright (C) 2001- Frank S. Nestel (frank at spieleck.de)

 This program 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 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 Lesser General Public License
 along with this program (lesser.txt); if not, write to the Free Software
 Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA  02111-1307, USA.
 */

/**
 * A very light (and therefore fast, efficient) implementation
 * of a CharSequence. Tailored for Ngram purpose.
 * @author frank nestel
 * @author $Author: nestefan $
 * @version $Revision: 2 $ $Date: 2006-03-27 23:00:21 +0200 (Mo, 27 Mrz 2006) $ $Author: nestefan $
 */
public class LightCharSequence
    implements CharSequence
{
    private char[] chars ;

    private int hashCode ;

    public LightCharSequence( CharSequence seq )
    {
        chars = new char[ seq.length() ] ;
        for ( int i = 0 ; i < chars.length ; i++ )
        {
            chars[ i ] = seq.charAt( i ) ;
        }
        calcHashCode() ;
    }

    public LightCharSequence( CharSequence seq , int start , int end )
    {
        chars = new char[ end - start ] ;
        for ( int i = start ; i < end ; i++ )
        {
            chars[ i ] = seq.charAt( i - start ) ;
        }
        calcHashCode() ;
    }

    protected void calcHashCode()
    {
        hashCode = 42 + length() ;
        for ( int i = 0 ; i < chars.length ; i++ )
        {
            hashCode = hashCode * 0x110001 + charAt( i ) + 1 ;
        }
    }

    public char charAt( int pos )
    {
        return chars[ pos ] ;
    }

    public int length()
    {
        return chars.length ;
    }

    public CharSequence subSequence( int start , int end )
    {
        return new LightCharSequence( this , start , end ) ;
    }

    public String toString()
    {
        return new String( chars ) ;
    }

    public boolean equals( Object o )
    {
        if ( !( o instanceof LightCharSequence ) )
        {
            return false ;
        }
        LightCharSequence l = (LightCharSequence)o ;

        if ( l.length() != length() )
        {
            return false ;
        }
        for ( int i = 0 ; i < length() ; i++ )
        {
            if ( l.charAt( i ) != charAt( i ) )
            {
                return false ;
            }
        }
        return true ;
    }

    public int hashCode()
    {
        return hashCode ;
    }
}