context.java

這是一個javascript 的 interpreter是了解 web browser的好材料

/* -*- Mode: java; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 4 -*-
 *
 * ***** BEGIN LICENSE BLOCK *****
 * Version: MPL 1.1/GPL 2.0
 *
 * The contents of this file are subject to the Mozilla Public License Version
 * 1.1 (the "License"); you may not use this file except in compliance with
 * the License. You may obtain a copy of the License at
 * http://www.mozilla.org/MPL/
 *
 * Software distributed under the License is distributed on an "AS IS" basis,
 * WITHOUT WARRANTY OF ANY KIND, either express or implied. See the License
 * for the specific language governing rights and limitations under the
 * License.
 *
 * The Original Code is Rhino code, released
 * May 6, 1999.
 *
 * The Initial Developer of the Original Code is
 * Netscape Communications Corporation.
 * Portions created by the Initial Developer are Copyright (C) 1997-2000
 * the Initial Developer. All Rights Reserved.
 *
 * Contributor(s):
 *    Bob Jervis
 *
 * Alternatively, the contents of this file may be used under the terms of
 * the GNU General Public License Version 2 or later (the "GPL"), in which
 * case the provisions of the GPL are applicable instead of those above. If
 * you wish to allow use of your version of this file only under the terms of
 * the GPL and not to allow others to use your version of this file under the
 * MPL, indicate your decision by deleting the provisions above and replacing
 * them with the notice and other provisions required by the GPL. If you do
 * not delete the provisions above, a recipient may use your version of this
 * file under either the MPL or the GPL.
 *
 * ***** END LICENSE BLOCK ***** */

// API class

package org.mozilla.javascript;

import java.beans.PropertyChangeEvent;
import java.beans.PropertyChangeListener;
import java.io.CharArrayWriter;
import java.io.IOException;
import java.io.PrintWriter;
import java.io.Reader;
import java.io.StringWriter;
import java.io.Writer;
import java.lang.reflect.InvocationTargetException;
import java.lang.reflect.Method;
import java.util.Hashtable;
import java.util.Locale;

import org.mozilla.javascript.debug.DebuggableScript;
import org.mozilla.javascript.debug.Debugger;
import org.mozilla.javascript.xml.XMLLib;

/**
 * This class represents the runtime context of an executing script.
 *
 * Before executing a script, an instance of Context must be created
 * and associated with the thread that will be executing the script.
 * The Context will be used to store information about the executing
 * of the script such as the call stack. Contexts are associated with
 * the current thread  using the {@link #call(ContextAction)}
 * or {@link #enter()} methods.<p>
 *
 * Different forms of script execution are supported. Scripts may be
 * evaluated from the source directly, or first compiled and then later
 * executed. Interactive execution is also supported.<p>
 *
 * Some aspects of script execution, such as type conversions and
 * object creation, may be accessed directly through methods of
 * Context.
 *
 * @see Scriptable
 * @author Norris Boyd
 * @author Brendan Eich
 */

public class Context
{
    /**
     * Language versions.
     *
     * All integral values are reserved for future version numbers.
     */

    /**
     * The unknown version.
     */
    public static final int VERSION_UNKNOWN =   -1;

    /**
     * The default version.
     */
    public static final int VERSION_DEFAULT =    0;

    /**
     * JavaScript 1.0
     */
    public static final int VERSION_1_0 =      100;

    /**
     * JavaScript 1.1
     */
    public static final int VERSION_1_1 =      110;

    /**
     * JavaScript 1.2
     */
    public static final int VERSION_1_2 =      120;

    /**
     * JavaScript 1.3
     */
    public static final int VERSION_1_3 =      130;

    /**
     * JavaScript 1.4
     */
    public static final int VERSION_1_4 =      140;

    /**
     * JavaScript 1.5
     */
    public static final int VERSION_1_5 =      150;

    /**
     * JavaScript 1.6
     */
    public static final int VERSION_1_6 =      160;

    /**
     * JavaScript 1.7
     */
    public static final int VERSION_1_7 =      170;

    /**
     * Controls behaviour of <tt>Date.prototype.getYear()</tt>.
     * If <tt>hasFeature(FEATURE_NON_ECMA_GET_YEAR)</tt> returns true,
     * Date.prototype.getYear subtructs 1900 only if 1900 <= date < 2000.
     * The default behavior of {@link #hasFeature(int)} is always to subtruct
     * 1900 as rquired by ECMAScript B.2.4.
     */
    public static final int FEATURE_NON_ECMA_GET_YEAR = 1;

    /**
     * Control if member expression as function name extension is available.
     * If <tt>hasFeature(FEATURE_MEMBER_EXPR_AS_FUNCTION_NAME)</tt> returns
     * true, allow <tt>function memberExpression(args) { body }</tt> to be
     * syntax sugar for <tt>memberExpression = function(args) { body }</tt>,
     * when memberExpression is not a simple identifier.
     * See ECMAScript-262, section 11.2 for definition of memberExpression.
     * By default {@link #hasFeature(int)} returns false.
     */
    public static final int FEATURE_MEMBER_EXPR_AS_FUNCTION_NAME = 2;

    /**
     * Control if reserved keywords are treated as identifiers.
     * If <tt>hasFeature(RESERVED_KEYWORD_AS_IDENTIFIER)</tt> returns true,
     * treat future reserved keyword (see  Ecma-262, section 7.5.3) as ordinary
     * identifiers but warn about this usage.
     *
     * By default {@link #hasFeature(int)} returns false.
     */
    public static final int FEATURE_RESERVED_KEYWORD_AS_IDENTIFIER = 3;

    /**
     * Control if <tt>toString()</tt> should returns the same result
     * as  <tt>toSource()</tt> when applied to objects and arrays.
     * If <tt>hasFeature(FEATURE_TO_STRING_AS_SOURCE)</tt> returns true,
     * calling <tt>toString()</tt> on JS objects gives the same result as
     * calling <tt>toSource()</tt>. That is it returns JS source with code
     * to create an object with all enumeratable fields of the original object
     * instead of printing <tt>[object <i>result of
     * {@link Scriptable#getClassName()}</i>]</tt>.
     * <p>
     * By default {@link #hasFeature(int)} returns true only if
     * the current JS version is set to {@link #VERSION_1_2}.
     */
    public static final int FEATURE_TO_STRING_AS_SOURCE = 4;

    /**
     * Control if properties <tt>__proto__</tt> and <tt>__parent__</tt>
     * are treated specially.
     * If <tt>hasFeature(FEATURE_PARENT_PROTO_PROPERTIES)</tt> returns true,
     * treat <tt>__parent__</tt> and <tt>__proto__</tt> as special properties.
     * <p>
     * The properties allow to query and set scope and prototype chains for the
     * objects. The special meaning of the properties is available
     * only when they are used as the right hand side of the dot operator.
     * For example, while <tt>x.__proto__ = y</tt> changes the prototype
     * chain of the object <tt>x</tt> to point to <tt>y</tt>,
     * <tt>x["__proto__"] = y</tt> simply assigns a new value to the property
     * <tt>__proto__</tt> in <tt>x</tt> even when the feature is on.
     *
     * By default {@link #hasFeature(int)} returns true.
     */
    public static final int FEATURE_PARENT_PROTO_PROPERTIES = 5;

	/**
	 * @deprecated In previous releases, this name was given to
	 * FEATURE_PARENT_PROTO_PROPERTIES.
	 */
    public static final int FEATURE_PARENT_PROTO_PROPRTIES = 5;
	
    /**
     * Control if support for E4X(ECMAScript for XML) extension is available.
     * If hasFeature(FEATURE_E4X) returns true, the XML syntax is available.
     * <p>
     * By default {@link #hasFeature(int)} returns true if
     * the current JS version is set to {@link #VERSION_DEFAULT}
     * or is at least {@link #VERSION_1_6}.
     * @since 1.6 Release 1
     */
    public static final int FEATURE_E4X = 6;

    /**
     * Control if dynamic scope should be used for name access.
     * If hasFeature(FEATURE_DYNAMIC_SCOPE) returns true, then the name lookup
     * during name resolution will use the top scope of the script or function
     * which is at the top of JS execution stack instead of the top scope of the
     * script or function from the current stack frame if the top scope of
     * the top stack frame contains the top scope of the current stack frame
     * on its prototype chain.
     * <p>
     * This is useful to define shared scope containing functions that can
     * be called from scripts and functions using private scopes.
     * <p>
     * By default {@link #hasFeature(int)} returns false.
     * @since 1.6 Release 1
     */
    public static final int FEATURE_DYNAMIC_SCOPE = 7;

    /**
     * Control if strict variable mode is enabled.
     * When the feature is on Rhino reports runtime errors if assignment
     * to a global variable that does not exist is executed. When the feature
     * is off such assignments creates new variable in the global scope  as
     * required by ECMA 262.
     * <p>
     * By default {@link #hasFeature(int)} returns false.
     * @since 1.6 Release 1
     */
    public static final int FEATURE_STRICT_VARS = 8;

    /**
     * Control if strict eval mode is enabled.
     * When the feature is on Rhino reports runtime errors if non-string
     * argument is passed to the eval function. When the feature is off
     * eval simply return non-string argument as is without performing any
     * evaluation as required by ECMA 262.
     * <p>
     * By default {@link #hasFeature(int)} returns false.
     * @since 1.6 Release 1
     */
    public static final int FEATURE_STRICT_EVAL = 9;

    /**
     * When the feature is on Rhino will add a "fileName" and "lineNumber"
     * properties to Error objects automatically. When the feature is off, you
     * have to explicitly pass them as the second and third argument to the
     * Error constructor. Note that neither behaviour is fully ECMA 262 
     * compliant (as 262 doesn't specify a three-arg constructor), but keeping 
     * the feature off results in Error objects that don't have
     * additional non-ECMA properties when constructed using the ECMA-defined
     * single-arg constructor and is thus desirable if a stricter ECMA 
     * compliance is desired, specifically adherence to the point 15.11.5. of
     * the standard.
     * <p>
     * By default {@link #hasFeature(int)} returns false.
     * @since 1.6 Release 6
     */
    public static final int FEATURE_LOCATION_INFORMATION_IN_ERROR = 10;

    /**
     * Controls whether JS 1.5 'strict mode' is enabled.
     * When the feature is on, Rhino reports more than a dozen different
     * warnings.  When the feature is off, these warnings are not generated.
     * FEATURE_STRICT_MODE implies FEATURE_STRICT_VARS and FEATURE_STRICT_EVAL.
     * <p>
     * By default {@link #hasFeature(int)} returns false.
     * @since 1.6 Release 6
     */
    public static final int FEATURE_STRICT_MODE = 11;

    /**
     * Controls whether a warning should be treated as an error.
     * @since 1.6 Release 6
     */
    public static final int FEATURE_WARNING_AS_ERROR = 12;

    /**
     * Enables enhanced access to Java. 
     * Specifically, controls whether private and protected members can be
     * accessed, and whether scripts can catch all Java exceptions.
     * <p>
     * Note that this feature should only be enabled for trusted scripts.
     * <p>
     * By default {@link #hasFeature(int)} returns false.
     * @since 1.7 Release 1
     */
    public static final int FEATURE_ENHANCED_JAVA_ACCESS = 13;


    public static final String languageVersionProperty = "language version";
    public static final String errorReporterProperty   = "error reporter";

    /**
     * Convenient value to use as zero-length array of objects.
     */
    public static final Object[] emptyArgs = ScriptRuntime.emptyArgs;

    /**
     * Create a new Context.
     *
     * Note that the Context must be associated with a thread before
     * it can be used to execute a script.
     * @deprecated use {@link ContextFactory#enter()} or 
     * {@link ContextFactory#call(ContextAction)} instead.
     */
    public Context()
    {
        this(ContextFactory.getGlobal());
    }
    
    Context(ContextFactory factory)
    {
        assert factory != null;
        this.factory = factory;
        setLanguageVersion(VERSION_DEFAULT);
        optimizationLevel = codegenClass != null ? 0 : -1;
        maximumInterpreterStackDepth = Integer.MAX_VALUE;
    }

    /**
     * Get the current Context.
     *
     * The current Context is per-thread; this method looks up
     * the Context associated with the current thread. <p>
     *
     * @return the Context associated with the current thread, or
     *         null if no context is associated with the current
     *         thread.
     * @see ContextFactory#enterContext()
     * @see ContextFactory#call(ContextAction)
     */
    public static Context getCurrentContext()
    {
        Object helper = VMBridge.instance.getThreadContextHelper();
        return VMBridge.instance.getContext(helper);
    }

    /**
     * Same as calling {@link ContextFactory#enterContext()} on the global