nativefunction.java

javascript语言的解释器源码

/* -*- Mode: java; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 4 -*-
 *
 * The contents of this file are subject to the Netscape 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/NPL/
 *
 * 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 Netscape are
 * Copyright (C) 1997-1999 Netscape Communications Corporation. All
 * Rights Reserved.
 *
 * Contributor(s):
 * Norris Boyd
 * Igor Bukanov
 * Roger Lawrence
 * Mike McCabe
 *
 * Alternatively, the contents of this file may be used under the
 * terms of the GNU Public License (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 NPL, indicate your decision by
 * deleting the provisions above and replace 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 NPL or the GPL.
 */

package org.mozilla.javascript;

import org.mozilla.javascript.debug.DebuggableScript;

/**
 * This class implements the Function native object.
 * See ECMA 15.3.
 * @author Norris Boyd
 */
public abstract class NativeFunction extends BaseFunction
{

    public final void initScriptFunction(Context cx, Scriptable scope)
    {
        ScriptRuntime.setFunctionProtoAndParent(this, scope);
    }

    /**
     * @param indent How much to indent the decompiled result
     *
     * @param flags Flags specifying format of decompilation output
     */
    final String decompile(int indent, int flags)
    {
        String encodedSource = getEncodedSource();
        if (encodedSource == null) {
            return super.decompile(indent, flags);
        } else {
            UintMap properties = new UintMap(1);
            properties.put(Decompiler.INITIAL_INDENT_PROP, indent);
            return Decompiler.decompile(encodedSource, flags, properties);
        }
    }

    public int getLength()
    {
        int paramCount = getParamCount();
        if (getLanguageVersion() != Context.VERSION_1_2) {
            return paramCount;
        }
        Context cx = Context.getContext();
        NativeCall activation = ScriptRuntime.findFunctionActivation(cx, this);
        if (activation == null) {
            return paramCount;
        }
        return activation.originalArgs.length;
    }

    public int getArity()
    {
        return getParamCount();
    }

    /**
     * @deprecated Use {@link BaseFunction#getFunctionName()} instead.
     * For backwards compatibility keep an old method name used by
     * Batik and possibly others.
     */
    public String jsGet_name()
    {
        return getFunctionName();
    }

    /**
     * Get encoded source string.
     */
    public String getEncodedSource()
    {
        return null;
    }

    public DebuggableScript getDebuggableView()
    {
        return null;
    }

    protected abstract int getLanguageVersion();

    /**
     * Get number of declared parameters. It should be 0 for scripts.
     */
    protected abstract int getParamCount();

    /**
     * Get number of declared parameters and variables defined through var
     * statements.
     */
    protected abstract int getParamAndVarCount();

    /**
     * Get parameter or variable name.
     * If <tt>index < {@link #getParamCount()}</tt>, then return the name of the
     * corresponding parameter. Otherwise returm the name of variable.
     */
    protected abstract String getParamOrVarName(int index);
}