C++ JSString类代码示例

/* |callee| requires a usage string provided by JS_DefineFunctionsWithHelp. */
void
js::ReportUsageError(JSContext* cx, HandleObject callee, const char* msg)
{
    const char* usageStr = "usage";
    PropertyName* usageAtom = Atomize(cx, usageStr, strlen(usageStr))->asPropertyName();
    RootedId id(cx, NameToId(usageAtom));
    DebugOnly<Shape*> shape = static_cast<Shape*>(callee->as<JSFunction>().lookup(cx, id));
    MOZ_ASSERT(!shape->configurable());
    MOZ_ASSERT(!shape->writable());
    MOZ_ASSERT(shape->hasDefaultGetter());

    RootedValue usage(cx);
    if (!JS_GetProperty(cx, callee, "usage", &usage))
        return;

    if (!usage.isString()) {
        JS_ReportError(cx, "%s", msg);
    } else {
        JSString* str = usage.toString();
        if (!str->ensureFlat(cx))
            return;
        AutoStableStringChars chars(cx);
        if (!chars.initTwoByte(cx, str))
            return;

        JS_ReportError(cx, "%s. Usage: %hs", msg, chars.twoByteRange().start().get());
    }
}

JSAtom *
SavedFrame::getSource()
{
    const Value &v = getReservedSlot(JSSLOT_SOURCE);
    JSString *s = v.toString();
    return &s->asAtom();
}

bool
JSCompartment::wrap(JSContext* cx, MutableHandleString strp)
{
    MOZ_ASSERT(!cx->runtime()->isAtomsCompartment(this));
    MOZ_ASSERT(cx->compartment() == this);

    /* If the string is already in this compartment, we are done. */
    JSString* str = strp;
    if (str->zoneFromAnyThread() == zone())
        return true;

    /* If the string is an atom, we don't have to copy. */
    if (str->isAtom()) {
        MOZ_ASSERT(str->isPermanentAtom() || str->zone()->isAtomsZone());
        return true;
    }

    /* Check the cache. */
    RootedValue key(cx, StringValue(str));
    if (WrapperMap::Ptr p = crossCompartmentWrappers.lookup(CrossCompartmentKey(key))) {
        strp.set(p->value().get().toString());
        return true;
    }

    /* No dice. Make a copy, and cache it. */
    JSString* copy = CopyStringPure(cx, str);
    if (!copy)
        return false;
    if (!putWrapper(cx, CrossCompartmentKey(key), StringValue(copy)))
        return false;

    strp.set(copy);
    return true;
}

// Overview: These functions convert a JSString from holding a string in rope form
// down to a simple String representation. It does so by building up the string
// backwards, since we want to avoid recursion, we expect that the tree structure
// representing the rope is likely imbalanced with more nodes down the left side
// (since appending to the string is likely more common) - and as such resolving
// in this fashion should minimize work queue size.  (If we built the queue forwards
// we would likely have to place all of the constituent StringImpls into the
// Vector before performing any concatenation, but by working backwards we likely
// only fill the queue with the number of substrings at any given level in a
// rope-of-ropes.)    
void JSRopeString::resolveRopeSlowCase8(LChar* buffer) const
{
    LChar* position = buffer + m_length; // We will be working backwards over the rope.
    Vector<JSString*, 32, UnsafeVectorOverflow> workQueue; // Putting strings into a Vector is only OK because there are no GC points in this method.
    
    for (size_t i = 0; i < s_maxInternalRopeLength && m_fibers[i]; ++i)
        workQueue.append(m_fibers[i].get());

    while (!workQueue.isEmpty()) {
        JSString* currentFiber = workQueue.last();
        workQueue.removeLast();

        if (currentFiber->isRope()) {
            JSRopeString* currentFiberAsRope = static_cast<JSRopeString*>(currentFiber);
            for (size_t i = 0; i < s_maxInternalRopeLength && currentFiberAsRope->m_fibers[i]; ++i)
                workQueue.append(currentFiberAsRope->m_fibers[i].get());
            continue;
        }

        StringImpl* string = static_cast<StringImpl*>(currentFiber->m_value.impl());
        unsigned length = string->length();
        position -= length;
        StringImpl::copyChars(position, string->characters8(), length);
    }

    ASSERT(buffer == position);
}

static JSObject *
CloneObject(JSContext *cx, HandleObject selfHostedObject)
{
    AutoCycleDetector detect(cx, selfHostedObject);
    if (!detect.init())
        return nullptr;
    if (detect.foundCycle()) {
        JS_ReportError(cx, "SelfHosted cloning cannot handle cyclic object graphs.");
        return nullptr;
    }

    RootedObject clone(cx);
    if (selfHostedObject->is<JSFunction>()) {
        RootedFunction selfHostedFunction(cx, &selfHostedObject->as<JSFunction>());
        bool hasName = selfHostedFunction->atom() != nullptr;
        // Arrow functions use the first extended slot for their lexical |this| value.
        JS_ASSERT(!selfHostedFunction->isArrow());
        js::gc::AllocKind kind = hasName
                                 ? JSFunction::ExtendedFinalizeKind
                                 : selfHostedFunction->getAllocKind();
        clone = CloneFunctionObject(cx, selfHostedFunction, cx->global(), kind, TenuredObject);
        // To be able to re-lazify the cloned function, its name in the
        // self-hosting compartment has to be stored on the clone.
        if (clone && hasName)
            clone->as<JSFunction>().setExtendedSlot(0, StringValue(selfHostedFunction->atom()));
    } else if (selfHostedObject->is<RegExpObject>()) {
        RegExpObject &reobj = selfHostedObject->as<RegExpObject>();
        RootedAtom source(cx, reobj.getSource());
        JS_ASSERT(source->isPermanentAtom());
        clone = RegExpObject::createNoStatics(cx, source, reobj.getFlags(), nullptr);
    } else if (selfHostedObject->is<DateObject>()) {
        clone = JS_NewDateObjectMsec(cx, selfHostedObject->as<DateObject>().UTCTime().toNumber());
    } else if (selfHostedObject->is<BooleanObject>()) {
        clone = BooleanObject::create(cx, selfHostedObject->as<BooleanObject>().unbox());
    } else if (selfHostedObject->is<NumberObject>()) {
        clone = NumberObject::create(cx, selfHostedObject->as<NumberObject>().unbox());
    } else if (selfHostedObject->is<StringObject>()) {
        JSString *selfHostedString = selfHostedObject->as<StringObject>().unbox();
        if (!selfHostedString->isFlat())
            MOZ_CRASH();
        RootedString str(cx, js_NewStringCopyN<CanGC>(cx,
                                                      selfHostedString->asFlat().chars(),
                                                      selfHostedString->asFlat().length()));
        if (!str)
            return nullptr;
        clone = StringObject::create(cx, str);
    } else if (selfHostedObject->is<ArrayObject>()) {
        clone = NewDenseEmptyArray(cx, nullptr, TenuredObject);
    } else {
        JS_ASSERT(selfHostedObject->isNative());
        clone = NewObjectWithGivenProto(cx, selfHostedObject->getClass(), nullptr, cx->global(),
                                        selfHostedObject->tenuredGetAllocKind(),
                                        SingletonObject);
    }
    if (!clone)
        return nullptr;
    if (!CloneProperties(cx, selfHostedObject, clone))
        return nullptr;
    return clone;
}

void
Shape::dump(JSContext *cx, FILE *fp) const
{
    jsid propid = this->propid();

    JS_ASSERT(!JSID_IS_VOID(propid));

    if (JSID_IS_INT(propid)) {
        fprintf(fp, "[%ld]", (long) JSID_TO_INT(propid));
    } else if (JSID_IS_DEFAULT_XML_NAMESPACE(propid)) {
        fprintf(fp, "<default XML namespace>");
    } else {
        JSLinearString *str;
        if (JSID_IS_ATOM(propid)) {
            str = JSID_TO_ATOM(propid);
        } else {
            JS_ASSERT(JSID_IS_OBJECT(propid));
            JSString *s = ToStringSlow<CanGC>(cx, IdToValue(propid));
            fputs("object ", fp);
            str = s ? s->ensureLinear(cx) : NULL;
        }
        if (!str)
            fputs("<error>", fp);
        else
            FileEscapedString(fp, str, '"');
    }

    fprintf(fp, " g/s %p/%p slot %d attrs %x ",
            JS_FUNC_TO_DATA_PTR(void *, base()->rawGetter),
            JS_FUNC_TO_DATA_PTR(void *, base()->rawSetter),
            hasSlot() ? slot() : -1, attrs);

    if (attrs) {
        int first = 1;
        fputs("(", fp);
#define DUMP_ATTR(name, display) if (attrs & JSPROP_##name) fputs(&(" " #display)[first], fp), first = 0
        DUMP_ATTR(ENUMERATE, enumerate);
        DUMP_ATTR(READONLY, readonly);
        DUMP_ATTR(PERMANENT, permanent);
        DUMP_ATTR(GETTER, getter);
        DUMP_ATTR(SETTER, setter);
        DUMP_ATTR(SHARED, shared);
#undef  DUMP_ATTR
        fputs(") ", fp);
    }

    fprintf(fp, "flags %x ", flags);
    if (flags) {
        int first = 1;
        fputs("(", fp);
#define DUMP_FLAG(name, display) if (flags & name) fputs(&(" " #display)[first], fp), first = 0
        DUMP_FLAG(HAS_SHORTID, has_shortid);
        DUMP_FLAG(IN_DICTIONARY, in_dictionary);
#undef  DUMP_FLAG
        fputs(") ", fp);
    }

    fprintf(fp, "shortid %d\n", maybeShortid());
}

JSAtom *
js_AtomizeChars(JSContext *cx, const jschar *chars, size_t length, uintN flags)
{
    JSString str;

    str.initFlat((jschar *)chars, length);
    return js_AtomizeString(cx, &str, ATOM_TMPSTR | flags);
}

void
Shape::dump(JSContext *cx, FILE *fp) const
{
    /* This is only used from gdb, so allowing GC here would just be confusing. */
    gc::AutoSuppressGC suppress(cx);

    jsid propid = this->propid();

    JS_ASSERT(!JSID_IS_VOID(propid));

    if (JSID_IS_INT(propid)) {
        fprintf(fp, "[%ld]", (long) JSID_TO_INT(propid));
    } else {
        JSLinearString *str;
        if (JSID_IS_ATOM(propid)) {
            str = JSID_TO_ATOM(propid);
        } else {
            JS_ASSERT(JSID_IS_OBJECT(propid));
            Value v = IdToValue(propid);
            JSString *s = ToStringSlow<NoGC>(cx, v);
            fputs("object ", fp);
            str = s ? s->ensureLinear(cx) : nullptr;
        }
        if (!str)
            fputs("<error>", fp);
        else
            FileEscapedString(fp, str, '"');
    }

    fprintf(fp, " g/s %p/%p slot %d attrs %x ",
            JS_FUNC_TO_DATA_PTR(void *, base()->rawGetter),
            JS_FUNC_TO_DATA_PTR(void *, base()->rawSetter),
            hasSlot() ? slot() : -1, attrs);

    if (attrs) {
        int first = 1;
        fputs("(", fp);
#define DUMP_ATTR(name, display) if (attrs & JSPROP_##name) fputs(&(" " #display)[first], fp), first = 0
        DUMP_ATTR(ENUMERATE, enumerate);
        DUMP_ATTR(READONLY, readonly);
        DUMP_ATTR(PERMANENT, permanent);
        DUMP_ATTR(GETTER, getter);
        DUMP_ATTR(SETTER, setter);
        DUMP_ATTR(SHARED, shared);
#undef  DUMP_ATTR
        fputs(") ", fp);
    }

    fprintf(fp, "flags %x ", flags);
    if (flags) {
        int first = 1;
        fputs("(", fp);
#define DUMP_FLAG(name, display) if (flags & name) fputs(&(" " #display)[first], fp), first = 0
        DUMP_FLAG(IN_DICTIONARY, in_dictionary);
#undef  DUMP_FLAG
        fputs(") ", fp);
    }
}

static JSObject *
CloneObject(JSContext *cx, JSObject *selfHostedObject, CloneMemory &clonedObjects)
{
    DependentAddPtr<CloneMemory> p(cx, clonedObjects, selfHostedObject);
    if (p)
        return p->value();
    RootedObject clone(cx);
    if (selfHostedObject->is<JSFunction>()) {
        JSFunction *selfHostedFunction = &selfHostedObject->as<JSFunction>();
        bool hasName = selfHostedFunction->atom() != nullptr;
        js::gc::AllocKind kind = hasName
                                 ? JSFunction::ExtendedFinalizeKind
                                 : selfHostedFunction->getAllocKind();
        clone = CloneFunctionObject(cx, HandleFunction::fromMarkedLocation(&selfHostedFunction),
                                    cx->global(), kind, TenuredObject);
        // To be able to re-lazify the cloned function, its name in the
        // self-hosting compartment has to be stored on the clone.
        if (clone && hasName)
            clone->as<JSFunction>().setExtendedSlot(0, StringValue(selfHostedFunction->atom()));
    } else if (selfHostedObject->is<RegExpObject>()) {
        RegExpObject &reobj = selfHostedObject->as<RegExpObject>();
        RootedAtom source(cx, reobj.getSource());
        JS_ASSERT(source->isPermanentAtom());
        clone = RegExpObject::createNoStatics(cx, source, reobj.getFlags(), nullptr);
    } else if (selfHostedObject->is<DateObject>()) {
        clone = JS_NewDateObjectMsec(cx, selfHostedObject->as<DateObject>().UTCTime().toNumber());
    } else if (selfHostedObject->is<BooleanObject>()) {
        clone = BooleanObject::create(cx, selfHostedObject->as<BooleanObject>().unbox());
    } else if (selfHostedObject->is<NumberObject>()) {
        clone = NumberObject::create(cx, selfHostedObject->as<NumberObject>().unbox());
    } else if (selfHostedObject->is<StringObject>()) {
        JSString *selfHostedString = selfHostedObject->as<StringObject>().unbox();
        if (!selfHostedString->isFlat())
            MOZ_CRASH();
        RootedString str(cx, js_NewStringCopyN<CanGC>(cx,
                                                      selfHostedString->asFlat().chars(),
                                                      selfHostedString->asFlat().length()));
        if (!str)
            return nullptr;
        clone = StringObject::create(cx, str);
    } else if (selfHostedObject->is<ArrayObject>()) {
        clone = NewDenseEmptyArray(cx, nullptr, TenuredObject);
    } else {
        JS_ASSERT(selfHostedObject->isNative());
        clone = NewObjectWithGivenProto(cx, selfHostedObject->getClass(), nullptr, cx->global(),
                                        selfHostedObject->tenuredGetAllocKind(),
                                        SingletonObject);
    }
    if (!clone)
        return nullptr;
    if (!p.add(cx, clonedObjects, selfHostedObject, clone))
        return nullptr;
    if (!CloneProperties(cx, selfHostedObject, clone, clonedObjects)) {
        clonedObjects.remove(selfHostedObject);
        return nullptr;
    }
    return clone;
}

JSAtom *
SavedFrame::getFunctionDisplayName()
{
    const Value &v = getReservedSlot(JSSLOT_FUNCTIONDISPLAYNAME);
    if (v.isNull())
        return nullptr;
    JSString *s = v.toString();
    return &s->asAtom();
}

bool JSString::getOwnPropertySlotByIndex(JSCell* cell, ExecState* exec, unsigned propertyName, PropertySlot& slot)
{
    JSString* thisObject = jsCast<JSString*>(cell);
    // The semantics here are really getPropertySlot, not getOwnPropertySlot.
    // This function should only be called by JSValue::get.
    if (thisObject->getStringPropertySlot(exec, propertyName, slot))
        return true;
    return JSString::getOwnPropertySlot(thisObject, exec, Identifier::from(exec, propertyName), slot);
}

void JSString::visitChildren(JSCell* cell, SlotVisitor& visitor)
{
    JSString* thisObject = asString(cell);
    Base::visitChildren(thisObject, visitor);
    
    if (thisObject->isRope())
        static_cast<JSRopeString*>(thisObject)->visitFibers(visitor);
    if (StringImpl* impl = thisObject->m_value.impl())
        visitor.reportExtraMemoryVisited(impl->costDuringGC());
}

JSAtom *
js::ToAtom(ExclusiveContext *cx, typename MaybeRooted<Value, allowGC>::HandleType v)
{
    if (!v.isString())
        return ToAtomSlow<allowGC>(cx, v);

    JSString *str = v.toString();
    if (str->isAtom())
        return &str->asAtom();

    return AtomizeString(cx, str);
}

static TriState equalToStringImpl(JSValue value, StringImpl* stringImpl)
{
    if (!value.isString())
        return FalseTriState;
    
    JSString* jsString = asString(value);
    const StringImpl* string = jsString->tryGetValueImpl();
    if (!string)
        return MixedTriState;
    
    return triState(WTF::equal(stringImpl, string));
}

JSBool
EvalScriptVersion16(JSContext *cx, uintN argc, jsval *vp)
{
    JS_ASSERT(argc == 1);
    jsval *argv = JS_ARGV(cx, vp);
    JS_ASSERT(JSVAL_IS_STRING(argv[0]));
    JSString *str = JSVAL_TO_STRING(argv[0]);
    const jschar *chars = str->getChars(cx);
    JS_ASSERT(chars);
    size_t len = str->length();
    return callbackData->evalVersion(chars, len, JSVERSION_1_6);
}