/* * USE - UML based specification environment * Copyright (C) 1999-2004 Mark Richters, University of Bremen * * This program 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 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 General Public License * along with this program; if not, write to the Free Software * Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA. *//* $ProjectHeader: use 2-3-0-release.1 Mon, 12 Sep 2005 20:18:33 +0200 green $ */package org.tzi.use.uml.ocl.expr;import java.io.PrintWriter;import java.util.Stack;import org.tzi.use.uml.ocl.value.Value;import org.tzi.use.uml.ocl.value.VarBindings;import org.tzi.use.uml.sys.MSystemState;import org.tzi.use.util.Log;/** * Context information used during evaluation. * * @version     $ProjectVersion: 2-3-0-release.1 $ * @author  Mark Richters */final class EvalContext {    private MSystemState fPreState; // required for postconditions    private MSystemState fPostState; // default state    private VarBindings fVarBindings;    private int fNesting;   // for indentation during trace    private PrintWriter fEvalLog; // may be null    private boolean fEnableEvalTree;    private Stack fNodeStack;    private EvalNode fRootNode;    /**     * Creates new evaluation context. The parameter preState may be     * null in which case it is set to postState.     */    EvalContext(MSystemState preState,                MSystemState postState,                VarBindings globalBindings,                PrintWriter evalLog) {        fPreState = preState;        fPostState = postState;        fVarBindings = new VarBindings(globalBindings);        fNesting = 0;        fEvalLog = evalLog;    }    /**     * Turns on building an evaluation tree. The tree is used, e.g.,     * in the evaluation browser.       */    void enableEvalTree() {        fEnableEvalTree = true;        fNodeStack = new Stack();    }    /**     * Pushes a new variable binding onto the binding stack.     */    void pushVarBinding(String varname, Value value) {        fVarBindings.push(varname, value);    }    /**     * Pops the last added variable binding from the binding stack.     */    void popVarBinding() {        fVarBindings.pop();    }    /**     * Returns current state of variable bindings (for debugging).     */    VarBindings varBindings() {        return fVarBindings;    }    /**     * Returns the current system state.     */    MSystemState postState() {        return fPostState;    }    /**     * Returns the prestate.     */    MSystemState preState() {        return fPreState;    }    /**      * Search current bindings for variable name. Visibility is     * determined by the order of elements. Variable bindings may thus     * be hidden by bindings at earlier positions.     *     * @return value for name binding or null if not bound     */    Value getVarValue(String name) {        return fVarBindings.getValue(name);    }    /**     * Returns the root node of the evaluation tree after evaluation     * is complete. Result is null, if building the tree has not been     * enabled before.     */    EvalNode getEvalNodeRoot() {        return fRootNode;    }    void enter(Expression expr) {        fNesting++;        if (Log.isTracing() ) {            String ec = expr.getClass().getName();            ec = ec.substring(ec.lastIndexOf(".") + 1);            Log.trace(this, indent() + "enter " + ec + " \"" + expr + "\"");        }        if (fEnableEvalTree )            fNodeStack.push(new EvalNode());    }    void exit(Expression expr, Value result) {        fNesting--;        if (Log.isTracing() ) {            Log.trace(this, indent() + "exit  \"" + expr + "\" = " + result);        }        // print the results sequentially from the innermost        // subexpression to the outermost expression        if (fEvalLog != null )            fEvalLog.println("  " + expr + " : " +                              result.type() + " = " + result);        if (fEnableEvalTree ) {            EvalNode n = (EvalNode) fNodeStack.pop();            n.setExpression(expr);            n.setResult(result);            if (! fNodeStack.empty() )                ((EvalNode) fNodeStack.peek()).addChild(n);            else                fRootNode = n;        }    }    private String indent() {        char[] indent = new char[fNesting];        for (int i = 0; i < fNesting; i++)            indent[i] = ' ';        return new String(indent);    }}