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/* SubstringFunction.java --

   Copyright (C) 2004 Free Software Foundation, Inc.

This file is part of GNU Classpath.

GNU Classpath 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; either version 2, or (at your option)

any later version.

GNU Classpath 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 GNU Classpath; see the file COPYING.  If not, write to the

Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA

02110-1301 USA.

Linking this library statically or dynamically with other modules is

making a combined work based on this library.  Thus, the terms and

conditions of the GNU General Public License cover the whole

combination.

As a special exception, the copyright holders of this library give you

permission to link this library with independent modules to produce an

executable, regardless of the license terms of these independent

modules, and to copy and distribute the resulting executable under

terms of your choice, provided that you also meet, for each linked

independent module, the terms and conditions of the license of that

module.  An independent module is a module which is not derived from

or based on this library.  If you modify this library, you may extend

this exception to your version of the library, but you are not

obligated to do so.  If you do not wish to do so, delete this

exception statement from your version. */

package gnu.xml.xpath;

import java.util.List;

import javax.xml.namespace.QName;

import org.w3c.dom.Node;

/**

 * The substring function returns the substring of the first argument

 * starting at the position specified in the second argument with length

 * specified in the third argument. For example, substring("12345",2,3)

 * returns "234". If the third argument is not specified, it returns the

 * substring starting at the position specified in the second argument and

 * continuing to the end of the string. For example, substring("12345",2)

 * returns "2345".

 *

 * @author <a href='mailto:dog@gnu.org'>Chris Burdess</a>

 */

final class SubstringFunction

  extends Expr

{

  final Expr arg1;

  final Expr arg2;

  final Expr arg3;

  SubstringFunction(List args)

  {

    this((Expr) args.get(0), (Expr) args.get(1),

         (args.size() > 2) ? (Expr) args.get(2) : null);

  }

  SubstringFunction(Expr arg1, Expr arg2, Expr arg3)

  {

    this.arg1 = arg1;

    this.arg2 = arg2;

    this.arg3 = arg3;

  }

  public Object evaluate(Node context, int pos, int len)

  {

    Object val1 = arg1.evaluate(context, pos, len);

    Object val2 = arg2.evaluate(context, pos, len);

    String s = _string(context, val1);

    int p = (val2 instanceof Double) ?

      ((Double) val2).intValue() :

        (int) Math.round(_number(context, val2));

    p--;

    if (p < 0)

      {

        p = 0;

      }

    int l = s.length() - p;

    if (l <= 0)

      {

        return "";

      }

    if (arg3 != null)

      {

        Object val3 = arg3.evaluate(context, pos, len);

        int v3 = (val3 instanceof Double) ?

          ((Double) val3).intValue() :

            (int) Math.round(_number(context, val3));

        if (v3 < l)

          {

            l = v3;

          }

      }

    return s.substring(p, p + l);

  }

  public Expr clone(Object context)

  {

    return new SubstringFunction(arg1.clone(context), arg2.clone(context),

                                 (arg3 == null) ? null : arg3.clone(context));

  }

  public boolean references(QName var)

  {

    return (arg1.references(var) || arg2.references(var) ||

            (arg3 == null) ? false : arg3.references(var));

  }

  public String toString()

  {

    return (arg3 == null) ? "substring(" + arg1 + "," + arg2 + ")" :

      "substring(" + arg1 + "," + arg2 + "," + arg3 + ")";

  }

}