gcc/libjava/gnu/xml/xpath/IdFunction.java

/* IdFunction.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.

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Free Software Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA
02111-1307 USA.

Linking this library statically or dynamically with other modules is
making a combined work based on this library.  Thus, the terms and
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permission to link this library with independent modules to produce an
executable, regardless of the license terms of these independent
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exception statement from your version. */

package gnu.xml.xpath;

import java.util.Collection;
import java.util.List;
import org.w3c.dom.Node;

/**
 * The <code>id</code> function selects elements by their unique ID.
 * When the argument to id is of type node-set, then the result is
 * the union of the result of applying id to the string-value of each of the
 * nodes in the argument node-set. When the argument to id is of any other
 * type, the argument is converted to a string as if by a call to the string
 * function; the string is split into a whitespace-separated list of tokens
 * (whitespace is any sequence of characters matching the production S); the
 * result is a node-set containing the elements in the same document as the
 * context node that have a unique ID equal to any of the tokens in the
 * list.
 *
 * @author <a href='mailto:dog@gnu.org'>Chris Burdess</a>
 */
public final class IdFunction
  extends Pattern
{

  final Expr arg;

  IdFunction(List args)
  {
    this((Expr) args.get(0));
  }

  public IdFunction(Expr arg)
  {
    this.arg = arg;
  }

  public boolean matches(Node context)
  {
    Object ret = evaluate(context, 1, 1);
    return !((Collection) ret).isEmpty();
  }

  public Object evaluate(Node context, int pos, int len)
  {
    Object val = arg.evaluate(context, pos, len);
    return _id(context, val);
  }

  public Expr clone(Object context)
  {
    return new IdFunction(arg.clone(context));
  }

  public String toString()
  {
    return "id(" + arg + ")";
  }
  
}