JJTParserState.java

/**
 *
 * This file is a part of ZOOLA - an extensible BeanShell implementation.
 * Zoola is based on original BeanShell code created by Pat Niemeyer.
 *
 * Original BeanShell code is Copyright (C) 2000 Pat Niemeyer <pat@pat.net>.
 *
 * New portions are Copyright 2012 Rafal Lewczuk <rafal.lewczuk@jitlogic.com>
 *
 * This 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 3 of the License, or (at your option) any later
 * version.
 *
 * This software 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 ZOOLA. If not, see <http://www.gnu.org/licenses/>.
 *
 */

package bsh;

import bsh.ast.Node;

class JJTParserState {
  private java.util.Stack nodes;
  private java.util.Stack marks;

  private int sp;		// number of nodes on stack
  private int mk;		// current mark
  private boolean node_created;

  JJTParserState() {
    nodes = new java.util.Stack();
    marks = new java.util.Stack();
    sp = 0;
    mk = 0;
  }

  /* Determines whether the current node was actually closed and
     pushed.  This should only be called in the final user action of a
     node scope.  */
  boolean nodeCreated() {
    return node_created;
  }

  /* Call this to reinitialize the node stack.  It is called
     automatically by the parser's ReInit() method. */
  void reset() {
    nodes.removeAllElements();
    marks.removeAllElements();
    sp = 0;
    mk = 0;
  }

  /* Returns the root node of the AST.  It only makes sense to call
     this after a successful parse. */
  Node rootNode() {
    return (Node)nodes.elementAt(0);
  }

  /* Pushes a node on to the stack. */
  void pushNode(Node n) {
    nodes.push(n);
    ++sp;
  }

  /* Returns the node on the top of the stack, and remove it from the
     stack.  */
  Node popNode() {
    if (--sp < mk) {
      mk = ((Integer)marks.pop()).intValue();
    }
    return (Node)nodes.pop();
  }

  /* Returns the node currently on the top of the stack. */
  Node peekNode() {
    return (Node)nodes.peek();
  }

  /* Returns the number of children on the stack in the current node
     scope. */
  int nodeArity() {
    return sp - mk;
  }


  void clearNodeScope(Node n) {
    while (sp > mk) {
      popNode();
    }
    mk = ((Integer)marks.pop()).intValue();
  }


  void openNodeScope(Node n) {
    marks.push(new Integer(mk));
    mk = sp;
    n.jjtOpen();
  }


  /* A definite node is constructed from a specified number of
     children.  That number of nodes are popped from the stack and
     made the children of the definite node.  Then the definite node
     is pushed on to the stack. */
  void closeNodeScope(Node n, int num) {
    mk = ((Integer)marks.pop()).intValue();
    while (num-- > 0) {
      Node c = popNode();
      c.jjtSetParent(n);
      n.jjtAddChild(c, num);
    }
    n.jjtClose();
    pushNode(n);
    node_created = true;
  }


  /* A conditional node is constructed if its condition is true.  All
     the nodes that have been pushed since the node was opened are
     made children of the the conditional node, which is then pushed
     on to the stack.  If the condition is false the node is not
     constructed and they are left on the stack. */
  void closeNodeScope(Node n, boolean condition) {
    if (condition) {
      int a = nodeArity();
      mk = ((Integer)marks.pop()).intValue();
      while (a-- > 0) {
	Node c = popNode();
	c.jjtSetParent(n);
	n.jjtAddChild(c, a);
      }
      n.jjtClose();
      pushNode(n);
      node_created = true;
    } else {
      mk = ((Integer)marks.pop()).intValue();
      node_created = false;
    }
  }
}