evalcontext.java

UML设计测试工具

/*
 * 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);
    }
}