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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.
/* -*- 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;
/**
* This class implements generator objects. See
* http://developer.mozilla.org/en/docs/New_in_JavaScript_1.7#Generators
*
* @author Norris Boyd
*/
public final class NativeGenerator extends IdScriptableObject {
private static final long serialVersionUID = 1645892441041347273L;
private static final Object GENERATOR_TAG = "Generator";
static NativeGenerator init(ScriptableObject scope, boolean sealed) {
// Generator
// Can't use "NativeGenerator().exportAsJSClass" since we don't want
// to define "Generator" as a constructor in the top-level scope.
NativeGenerator prototype = new NativeGenerator();
if (scope != null) {
prototype.setParentScope(scope);
prototype.setPrototype(getObjectPrototype(scope));
}
prototype.activatePrototypeMap(MAX_PROTOTYPE_ID);
if (sealed) {
prototype.sealObject();
}
// Need to access Generator prototype when constructing
// Generator instances, but don't have a generator constructor
// to use to find the prototype. Use the "associateValue"
// approach instead.
if (scope != null) {
scope.associateValue(GENERATOR_TAG, prototype);
}
return prototype;
}
/** Only for constructing the prototype object. */
private NativeGenerator() {}
public NativeGenerator(Scriptable scope, NativeFunction function, Object savedState) {
this.function = function;
this.savedState = savedState;
// Set parent and prototype properties. Since we don't have a
// "Generator" constructor in the top scope, we stash the
// prototype in the top scope's associated value.
Scriptable top = ScriptableObject.getTopLevelScope(scope);
this.setParentScope(top);
NativeGenerator prototype =
(NativeGenerator) ScriptableObject.getTopScopeValue(top, GENERATOR_TAG);
this.setPrototype(prototype);
}
public static final int GENERATOR_SEND = 0, GENERATOR_THROW = 1, GENERATOR_CLOSE = 2;
@Override
public String getClassName() {
return "Generator";
}
@Override
protected void initPrototypeId(int id) {
String s;
int arity;
switch (id) {
case Id_close:
arity = 1;
s = "close";
break;
case Id_next:
arity = 1;
s = "next";
break;
case Id_send:
arity = 0;
s = "send";
break;
case Id_throw:
arity = 0;
s = "throw";
break;
case Id___iterator__:
arity = 1;
s = "__iterator__";
break;
default:
throw new IllegalArgumentException(String.valueOf(id));
}
initPrototypeMethod(GENERATOR_TAG, id, s, arity);
}
@Override
public Object execIdCall(
IdFunctionObject f, Context cx, Scriptable scope, Scriptable thisObj, Object[] args) {
if (!f.hasTag(GENERATOR_TAG)) {
return super.execIdCall(f, cx, scope, thisObj, args);
}
int id = f.methodId();
NativeGenerator generator = ensureType(thisObj, NativeGenerator.class, f);
switch (id) {
case Id_close:
// need to run any pending finally clauses
return generator.resume(cx, scope, GENERATOR_CLOSE, new GeneratorClosedException());
case Id_next:
// arguments to next() are ignored
generator.firstTime = false;
return generator.resume(cx, scope, GENERATOR_SEND, Undefined.instance);
case Id_send:
{
Object arg = args.length > 0 ? args[0] : Undefined.instance;
if (generator.firstTime && !arg.equals(Undefined.instance)) {
throw ScriptRuntime.typeErrorById("msg.send.newborn");
}
return generator.resume(cx, scope, GENERATOR_SEND, arg);
}
case Id_throw:
return generator.resume(
cx, scope, GENERATOR_THROW, args.length > 0 ? args[0] : Undefined.instance);
case Id___iterator__:
return thisObj;
default:
throw new IllegalArgumentException(String.valueOf(id));
}
}
private Object resume(Context cx, Scriptable scope, int operation, Object value) {
if (savedState == null) {
if (operation == GENERATOR_CLOSE) return Undefined.instance;
Object thrown;
if (operation == GENERATOR_THROW) {
thrown = value;
} else {
thrown = NativeIterator.getStopIterationObject(scope);
}
throw new JavaScriptException(thrown, lineSource, lineNumber);
}
try {
synchronized (this) {
// generator execution is necessarily single-threaded and
// non-reentrant.
// See https://bugzilla.mozilla.org/show_bug.cgi?id=349263
if (locked) throw ScriptRuntime.typeErrorById("msg.already.exec.gen");
locked = true;
}
return function.resumeGenerator(cx, scope, operation, savedState, value);
} catch (GeneratorClosedException e) {
// On closing a generator in the compile path, the generator
// throws a special exception. This ensures execution of all pending
// finalizers and will not get caught by user code.
return Undefined.instance;
} catch (RhinoException e) {
lineNumber = e.lineNumber();
lineSource = e.lineSource();
savedState = null;
throw e;
} finally {
synchronized (this) {
locked = false;
}
if (operation == GENERATOR_CLOSE) savedState = null;
}
}
@Override
protected int findPrototypeId(String s) {
int id;
switch (s) {
case "close":
id = Id_close;
break;
case "next":
id = Id_next;
break;
case "send":
id = Id_send;
break;
case "throw":
id = Id_throw;
break;
case "__iterator__":
id = Id___iterator__;
break;
default:
id = 0;
break;
}
return id;
}
private static final int Id_close = 1,
Id_next = 2,
Id_send = 3,
Id_throw = 4,
Id___iterator__ = 5,
MAX_PROTOTYPE_ID = 5;
private NativeFunction function;
private Object savedState;
private String lineSource;
private int lineNumber;
private boolean firstTime = true;
private boolean locked;
public static class GeneratorClosedException extends RuntimeException {
private static final long serialVersionUID = 2561315658662379681L;
}
}
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