/*
 * $Id$
 *
 * Copyright (C) 2003-2015 JNode.org
 *
 * 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 library; If not, write to the Free Software Foundation, Inc., 
 * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
 */
 
package org.jnode.vm.classmgr;

import org.jnode.vm.objects.VmSystemObject;

/**
 * @author epr
 */
public class VmLineNumberMap extends VmSystemObject {

    /**
     * Line number table. The line-number table should be interpreted as
     * follows: Each line number entry consists of two entries in the following
     * array. Entry i*2+0 = start_pc Entry i*2+1 = line_number So lnTable.length ==
     * noLineNrs*2
     */
    private final char[] lnTable;

    public static final int LNT_STARTPC_OFS = 0;

    public static final int LNT_LINENR_OFS = 1;

    public static final int LNT_ELEMSIZE = 2;

    public VmLineNumberMap(char[] lnTable) {
        this.lnTable = lnTable;
    }

    /**
     * Gets the number of entries of this table
     *
     * @return length of the table
     */
    public int getLength() {
        return (lnTable == null) ? 0 : (lnTable.length / LNT_ELEMSIZE);
    }

    /**
     * Gets the start PC field of an entry in this table with a given index.
     *
     * @param index
     * @return int
     */
    public int getStartPCAt(int index) {
        return lnTable[index * LNT_ELEMSIZE + LNT_STARTPC_OFS];
    }

    /**
     * Gets the line number field of an entry in this table with a given index.
     *
     * @param index
     * @return int
     */
    public int getLineNrAt(int index) {
        return lnTable[index * LNT_ELEMSIZE + LNT_LINENR_OFS];
    }

    /**
     * Gets the linenumber for a given PC.
     *
     * @param pc
     * @return The line number
     */
    public int findLineNr(int pc) {
        int ln = 0;
        if (lnTable != null) {
            final int len = lnTable.length;
            for (int i = 0; i < len; i += LNT_ELEMSIZE) {
                final char startPC = lnTable[i + LNT_STARTPC_OFS];
                final char lineNr = lnTable[i + LNT_LINENR_OFS];
                if (startPC <= pc) {
                    ln = lineNr;
                } else {
                    return ln;
                }
            }
        }
        return ln;
    }

}