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Rhino is an open-source implementation of JavaScript written entirely in Java. It is typically embedded into Java applications to provide scripting to end users.
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/* -*- Mode: java; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 4 -*-
 *
 * This Source Code Form is subject to the terms of the Mozilla Public
 * License, v. 2.0. If a copy of the MPL was not distributed with this
 * file, You can obtain one at http://mozilla.org/MPL/2.0/. */

package org.mozilla.javascript;

import java.util.Objects;

public final class NativeContinuation extends IdScriptableObject implements Function {
    private static final long serialVersionUID = 1794167133757605367L;

    private static final Object FTAG = "Continuation";

    private Object implementation;

    public static void init(Context cx, Scriptable scope, boolean sealed) {
        NativeContinuation obj = new NativeContinuation();
        obj.exportAsJSClass(MAX_PROTOTYPE_ID, scope, sealed);
    }

    public Object getImplementation() {
        return implementation;
    }

    public void initImplementation(Object implementation) {
        this.implementation = implementation;
    }

    @Override
    public String getClassName() {
        return "Continuation";
    }

    @Override
    public Scriptable construct(Context cx, Scriptable scope, Object[] args) {
        throw Context.reportRuntimeError("Direct call is not supported");
    }

    @Override
    public Object call(Context cx, Scriptable scope, Scriptable thisObj, Object[] args) {
        return Interpreter.restartContinuation(this, cx, scope, args);
    }

    public static boolean isContinuationConstructor(IdFunctionObject f) {
        if (f.hasTag(FTAG) && f.methodId() == Id_constructor) {
            return true;
        }
        return false;
    }

    /**
     * Returns true if both continuations have equal implementations.
     *
     * @param c1 one continuation
     * @param c2 another continuation
     * @return true if the implementations of both continuations are equal, or they are both null.
     * @throws NullPointerException if either continuation is null
     */
    public static boolean equalImplementations(NativeContinuation c1, NativeContinuation c2) {
        return Objects.equals(c1.implementation, c2.implementation);
    }

    @Override
    protected void initPrototypeId(int id) {
        String s;
        int arity;
        switch (id) {
            case Id_constructor:
                arity = 0;
                s = "constructor";
                break;
            default:
                throw new IllegalArgumentException(String.valueOf(id));
        }
        initPrototypeMethod(FTAG, id, s, arity);
    }

    @Override
    public Object execIdCall(
            IdFunctionObject f, Context cx, Scriptable scope, Scriptable thisObj, Object[] args) {
        if (!f.hasTag(FTAG)) {
            return super.execIdCall(f, cx, scope, thisObj, args);
        }
        int id = f.methodId();
        switch (id) {
            case Id_constructor:
                throw Context.reportRuntimeError("Direct call is not supported");
        }
        throw new IllegalArgumentException(String.valueOf(id));
    }

    @Override
    protected int findPrototypeId(String s) {
        int id;
        switch (s) {
            case "constructor":
                id = Id_constructor;
                break;
            default:
                id = 0;
                break;
        }
        return id;
    }

    private static final int Id_constructor = 1, MAX_PROTOTYPE_ID = 1;
}