C++ JSValue::isNull方法代码示例

static EncodedJSValue JSC_HOST_CALL webAssemblyTableProtoFuncSet(ExecState* exec)
{
    VM& vm = exec->vm();
    auto throwScope = DECLARE_THROW_SCOPE(vm);

    JSWebAssemblyTable* table = getTable(exec, vm, exec->thisValue());
    RETURN_IF_EXCEPTION(throwScope, encodedJSValue());

    JSValue value = exec->argument(1);
    WebAssemblyFunction* wasmFunction;
    WebAssemblyWrapperFunction* wasmWrapperFunction;
    if (!value.isNull() && !isWebAssemblyHostFunction(vm, value, wasmFunction, wasmWrapperFunction))
        return JSValue::encode(throwException(exec, throwScope, createTypeError(exec, "WebAssembly.Table.prototype.set expects the second argument to be null or an instance of WebAssembly.Function"_s)));

    uint32_t index = toNonWrappingUint32(exec, exec->argument(0));
    RETURN_IF_EXCEPTION(throwScope, encodedJSValue());

    if (index >= table->length())
        return JSValue::encode(throwException(exec, throwScope, createRangeError(exec, "WebAssembly.Table.prototype.set expects an integer less than the length of the table"_s)));

    if (value.isNull())
        table->clearFunction(index);
    else {
        ASSERT(value.isObject() && isWebAssemblyHostFunction(vm, jsCast<JSObject*>(value), wasmFunction, wasmWrapperFunction));
        ASSERT(!!wasmFunction || !!wasmWrapperFunction);
        if (wasmFunction)
            table->setFunction(vm, index, wasmFunction);
        else
            table->setFunction(vm, index, wasmWrapperFunction);
    }
    
    return JSValue::encode(jsUndefined());
}

// ECMA 8.6.2.2
void JSObject::put(ExecState* exec, const Identifier& propertyName, JSValue value, PutPropertySlot& slot)
{
    ASSERT(value);
    ASSERT(!Heap::heap(value) || Heap::heap(value) == Heap::heap(this));

    if (propertyName == exec->propertyNames().underscoreProto) {
        // Setting __proto__ to a non-object, non-null value is silently ignored to match Mozilla.
        if (!value.isObject() && !value.isNull())
            return;
        if (!setPrototypeWithCycleCheck(value))
            throwError(exec, createError(exec, "cyclic __proto__ value"));
        return;
    }

    // Check if there are any setters or getters in the prototype chain
    JSValue prototype;
    for (JSObject* obj = this; !obj->structure()->hasGetterSetterProperties(); obj = asObject(prototype)) {
        prototype = obj->prototype();
        if (prototype.isNull()) {
            putDirectInternal(exec->globalData(), propertyName, value, 0, true, slot);
            return;
        }
    }
    
    unsigned attributes;
    JSCell* specificValue;
    if ((m_structure->get(propertyName, attributes, specificValue) != WTF::notFound) && attributes & ReadOnly)
        return;

    for (JSObject* obj = this; ; obj = asObject(prototype)) {
        if (JSValue gs = obj->getDirect(propertyName)) {
            if (gs.isGetterSetter()) {
                JSObject* setterFunc = asGetterSetter(gs)->setter();        
                if (!setterFunc) {
                    throwSetterError(exec);
                    return;
                }
                
                CallData callData;
                CallType callType = setterFunc->getCallData(callData);
                MarkedArgumentBuffer args;
                args.append(value);
                call(exec, setterFunc, callType, callData, this, args);
                return;
            }

            // If there's an existing property on the object or one of its 
            // prototypes it should be replaced, so break here.
            break;
        }

        prototype = obj->prototype();
        if (prototype.isNull())
            break;
    }

    putDirectInternal(exec->globalData(), propertyName, value, 0, true, slot);
    return;
}

// ECMA 8.7.2
bool JSValue::putToPrimitive(ExecState* exec, PropertyName propertyName, JSValue value, PutPropertySlot& slot)
{
    VM& vm = exec->vm();
    auto scope = DECLARE_THROW_SCOPE(vm);

    if (Optional<uint32_t> index = parseIndex(propertyName))
        return putToPrimitiveByIndex(exec, index.value(), value, slot.isStrictMode());

    // Check if there are any setters or getters in the prototype chain
    JSObject* obj = synthesizePrototype(exec);
    if (UNLIKELY(!obj))
        return false;
    JSValue prototype;
    if (propertyName != exec->propertyNames().underscoreProto) {
        for (; !obj->structure()->hasReadOnlyOrGetterSetterPropertiesExcludingProto(); obj = asObject(prototype)) {
            prototype = obj->getPrototypeDirect();
            if (prototype.isNull()) {
                if (slot.isStrictMode())
                    throwTypeError(exec, scope, StrictModeReadonlyPropertyWriteError);
                return false;
            }
        }
    }

    for (; ; obj = asObject(prototype)) {
        unsigned attributes;
        PropertyOffset offset = obj->structure()->get(vm, propertyName, attributes);
        if (offset != invalidOffset) {
            if (attributes & ReadOnly) {
                if (slot.isStrictMode())
                    throwTypeError(exec, scope, StrictModeReadonlyPropertyWriteError);
                return false;
            }

            JSValue gs = obj->getDirect(offset);
            if (gs.isGetterSetter())
                return callSetter(exec, *this, gs, value, slot.isStrictMode() ? StrictMode : NotStrictMode);

            if (gs.isCustomGetterSetter())
                return callCustomSetter(exec, gs, attributes & CustomAccessor, obj, slot.thisValue(), value);

            // If there's an existing property on the object or one of its 
            // prototypes it should be replaced, so break here.
            break;
        }

        prototype = obj->getPrototype(vm, exec);
        if (vm.exception())
            return false;
        if (prototype.isNull())
            break;
    }
    
    if (slot.isStrictMode())
        throwTypeError(exec, scope, StrictModeReadonlyPropertyWriteError);
    return false;
}

bool Structure::prototypeChainMayInterceptStoreTo(JSGlobalData& globalData, PropertyName propertyName)
{
    unsigned i = propertyName.asIndex();
    if (i != PropertyName::NotAnIndex)
        return anyObjectInChainMayInterceptIndexedAccesses();
    
    for (Structure* current = this; ;) {
        JSValue prototype = current->storedPrototype();
        if (prototype.isNull())
            return false;
        
        current = prototype.asCell()->structure();
        
        unsigned attributes;
        JSCell* specificValue;
        PropertyOffset offset = current->get(globalData, propertyName, attributes, specificValue);
        if (!JSC::isValidOffset(offset))
            continue;
        
        if (attributes & (ReadOnly | Accessor))
            return true;
        
        return false;
    }
}

JSValue JSDOMWindow::atob(ExecState* exec, const ArgList& args)
{
    if (args.size() < 1)
        return throwError(exec, SyntaxError, "Not enough arguments");

    JSValue v = args.at(0);
    if (v.isNull())
        return jsEmptyString(exec);

    UString s = v.toString(exec);
    if (!s.is8Bit()) {
        setDOMException(exec, INVALID_CHARACTER_ERR);
        return jsUndefined();
    }

    Vector<char> in(s.size());
    for (int i = 0; i < s.size(); ++i)
        in[i] = static_cast<char>(s.data()[i]);
    Vector<char> out;

    if (!base64Decode(in, out))
        return throwError(exec, GeneralError, "Cannot decode base64");

    return jsString(exec, String(out.data(), out.size()));
}

RuntimeType runtimeTypeForValue(JSValue value)
{
    if (UNLIKELY(!value))
        return TypeNothing;

    if (value.isUndefined())
        return TypeUndefined;
    if (value.isNull())
        return TypeNull;
    if (value.isAnyInt())
        return TypeAnyInt;
    if (value.isNumber())
        return TypeNumber;
    if (value.isString())
        return TypeString;
    if (value.isBoolean())
        return TypeBoolean;
    if (value.isObject())
        return TypeObject;
    if (value.isFunction())
        return TypeFunction;
    if (value.isSymbol())
        return TypeSymbol;

    return TypeNothing;
}

JSValue JSCommandLineAPIHost::getEventListeners(ExecState& state)
{
    if (state.argumentCount() < 1)
        return jsUndefined();

    JSValue value = state.uncheckedArgument(0);
    if (!value.isObject() || value.isNull())
        return jsUndefined();

    Node* node = JSNode::toWrapped(value);
    if (!node)
        return jsUndefined();

    Vector<EventListenerInfo> listenersArray;
    wrapped().getEventListenersImpl(node, listenersArray);

    JSObject* result = constructEmptyObject(&state);
    for (size_t i = 0; i < listenersArray.size(); ++i) {
        JSArray* listeners = getJSListenerFunctions(state, &node->document(), listenersArray[i]);
        if (!listeners->length())
            continue;
        AtomicString eventType = listenersArray[i].eventType;
        result->putDirect(state.vm(), Identifier::fromString(&state, eventType.impl()), JSValue(listeners));
    }

    return result;
}

 void dumpImmediate(JSValue value)
 {
     if (value.isNull())
         write(NullTag);
     else if (value.isUndefined())
         write(UndefinedTag);
     else if (value.isNumber()) {
         if (value.isInt32()) {
             if (!value.asInt32())
                 write(ZeroTag);
             else if (value.asInt32() == 1)
                 write(OneTag);
             else {
                 write(IntTag);
                 write(static_cast<uint32_t>(value.asInt32()));
             }
         } else {
             write(DoubleTag);
             write(value.asDouble());
         }
     } else if (value.isBoolean()) {
         if (value.isTrue())
             write(TrueTag);
         else
             write(FalseTag);
     }
 }

JSValue JSInjectedScriptHost::getEventListeners(ExecState* exec)
{
    if (exec->argumentCount() < 1)
        return jsUndefined();
    JSValue value = exec->argument(0);
    if (!value.isObject() || value.isNull())
        return jsUndefined();
    Node* node = toNode(value);
    if (!node)
        return jsUndefined();
    // This can only happen for orphan DocumentType nodes.
    Document* document = node->document();
    if (!node->document())
        return jsUndefined();

    Vector<EventListenerInfo> listenersArray;
    impl()->getEventListenersImpl(node, listenersArray);

    JSObject* result = constructEmptyObject(exec);
    for (size_t i = 0; i < listenersArray.size(); ++i) {
        JSArray* listeners = getJSListenerFunctions(exec, document, listenersArray[i]);
        if (!listeners->length())
            continue;
        AtomicString eventType = listenersArray[i].eventType;
        result->putDirect(exec->globalData(), Identifier(exec, eventType.impl()), JSValue(listeners));
    }

    return result;
}

RuntimeType TypeSet::getRuntimeTypeForValue(JSValue v)
{
    RuntimeType ret;
    if (v.isFunction())
        ret = TypeFunction;
    else if (v.isUndefined())
        ret = TypeUndefined;
    else if (v.isNull())
        ret = TypeNull;
    else if (v.isBoolean())
        ret = TypeBoolean;
    else if (v.isMachineInt())
        ret = TypeMachineInt;
    else if (v.isNumber())
        ret = TypeNumber;
    else if (v.isString())
        ret = TypeString;
    else if (v.isPrimitive())
        ret = TypePrimitive;
    else if (v.isObject())
        ret = TypeObject;
    else
        CRASH();

    return ret;
}

bool JSValueIsNull(JSContextRef ctx, JSValueRef value)
{
    ExecState* exec = toJS(ctx);
    APIEntryShim entryShim(exec);

    JSValue jsValue = toJS(exec, value);
    return jsValue.isNull();
}

void JSHTMLDataGridElement::setDataSource(ExecState*, JSValue value)
{
    if (value.isNull()) {
        static_cast<HTMLDataGridElement*>(impl())->setDataSource(0);
        return;
    }

    static_cast<HTMLDataGridElement*>(impl())->setDataSource(JSDataGridDataSource::create(value, impl()->document()->frame()));
}

bool JSValueIsNull(JSContextRef ctx, JSValueRef value)
{
    ExecState* exec = toJS(ctx);
    exec->globalData().heap.registerThread();
    JSLock lock(exec);

    JSValue jsValue = toJS(exec, value);
    return jsValue.isNull();
}

std::unique_ptr<PolyProtoAccessChain> PolyProtoAccessChain::create(JSGlobalObject* globalObject, JSCell* base, JSObject* target, bool& usesPolyProto)
{
    JSCell* current = base;
    VM& vm = *base->vm();

    bool found = false;

    usesPolyProto = false;

    std::unique_ptr<PolyProtoAccessChain> result(new PolyProtoAccessChain());

    for (unsigned iterationNumber = 0; true; ++iterationNumber) {
        Structure* structure = current->structure(vm);

        if (!structure->propertyAccessesAreCacheable())
            return nullptr;

        if (structure->isProxy())
            return nullptr;

        if (structure->isDictionary()) {
            ASSERT(structure->isObject());
            if (structure->hasBeenFlattenedBefore())
                return nullptr;

            structure->flattenDictionaryStructure(vm, asObject(current));
        }

        // To save memory, we don't include the base in the chain. We let
        // AccessCase provide the base to us as needed.
        if (iterationNumber)
            result->m_chain.append(structure);
        else
            RELEASE_ASSERT(current == base);

        if (current == target) {
            found = true;
            break;
        }

        // We only have poly proto if we need to access our prototype via
        // the poly proto protocol. If the slot base is the only poly proto
        // thing in the chain, and we have a cache hit on it, then we're not
        // poly proto.
        usesPolyProto |= structure->hasPolyProto();

        JSValue prototype = structure->prototypeForLookup(globalObject, current);
        if (prototype.isNull())
            break;
        current = asObject(prototype);
    }

    if (!found && !!target)
        return nullptr;

    return result;
}

IntendedStructureChain::IntendedStructureChain(JSGlobalObject* globalObject, Structure* head)
    : m_globalObject(globalObject)
    , m_head(head)
{
    JSValue prototype = head->prototypeForLookup(globalObject);
    if (prototype.isNull())
        return;
    for (Structure* current = asObject(prototype)->structure(); current; current = current->storedPrototypeStructure())
        m_vector.append(current);
}