C++ PropertyDescriptor::isDataDescriptor方法代码示例

EncodedJSValue JSC_HOST_CALL objectConstructorIsFrozen(ExecState* exec)
{
    // 1. If Type(O) is not Object throw a TypeError exception.
    JSValue obj = exec->argument(0);
    if (!obj.isObject())
        return throwVMError(exec, createTypeError(exec, ASCIILiteral("Object.isFrozen can only be called on Objects.")));
    JSObject* object = asObject(obj);

    if (isJSFinalObject(object))
        return JSValue::encode(jsBoolean(object->isFrozen(exec->vm())));

    // 2. For each named own property name P of O,
    PropertyNameArray properties(exec);
    object->methodTable()->getOwnPropertyNames(object, exec, properties, IncludeDontEnumProperties);
    PropertyNameArray::const_iterator end = properties.end();
    for (PropertyNameArray::const_iterator iter = properties.begin(); iter != end; ++iter) {
        // a. Let desc be the result of calling the [[GetOwnProperty]] internal method of O with P.
        PropertyDescriptor desc;
        if (!object->methodTable()->getOwnPropertyDescriptor(object, exec, *iter, desc))
            continue;
        // b. If IsDataDescriptor(desc) is true then
        // i. If desc.[[Writable]] is true, return false. c. If desc.[[Configurable]] is true, then return false.
        if ((desc.isDataDescriptor() && desc.writable()) || desc.configurable())
            return JSValue::encode(jsBoolean(false));
    }

    // 3. If the [[Extensible]] internal property of O is false, then return true.
    // 4. Otherwise, return false.
    return JSValue::encode(jsBoolean(!object->isExtensible()));
}

static JSValue defineProperties(ExecState* exec, JSObject* object, JSObject* properties)
{
    PropertyNameArray propertyNames(exec);
    asObject(properties)->methodTable()->getOwnPropertyNames(asObject(properties), exec, propertyNames, ExcludeDontEnumProperties);
    size_t numProperties = propertyNames.size();
    Vector<PropertyDescriptor> descriptors;
    MarkedArgumentBuffer markBuffer;
    for (size_t i = 0; i < numProperties; i++) {
        PropertySlot slot;
        JSValue prop = properties->get(exec, propertyNames[i]);
        if (exec->hadException())
            return jsNull();
        PropertyDescriptor descriptor;
        if (!toPropertyDescriptor(exec, prop, descriptor))
            return jsNull();
        descriptors.append(descriptor);
        // Ensure we mark all the values that we're accumulating
        if (descriptor.isDataDescriptor() && descriptor.value())
            markBuffer.append(descriptor.value());
        if (descriptor.isAccessorDescriptor()) {
            if (descriptor.getter())
                markBuffer.append(descriptor.getter());
            if (descriptor.setter())
                markBuffer.append(descriptor.setter());
        }
    }
    for (size_t i = 0; i < numProperties; i++) {
        object->methodTable()->defineOwnProperty(object, exec, propertyNames[i], descriptors[i], true);
        if (exec->hadException())
            return jsNull();
    }
    return object;
}

static bool putDescriptor(ExecState* exec, JSObject* target, const Identifier& propertyName, PropertyDescriptor& descriptor, unsigned attributes, JSValue oldValue)
{
    if (descriptor.isGenericDescriptor() || descriptor.isDataDescriptor()) {
        target->putWithAttributes(exec, propertyName, descriptor.value() ? descriptor.value() : oldValue, attributes & ~(Getter | Setter));
        return true;
    }
    attributes &= ~ReadOnly;
    if (descriptor.getter() && descriptor.getter().isObject())
        target->defineGetter(exec, propertyName, asObject(descriptor.getter()), attributes);
    if (exec->hadException())
        return false;
    if (descriptor.setter() && descriptor.setter().isObject())
        target->defineSetter(exec, propertyName, asObject(descriptor.setter()), attributes);
    return !exec->hadException();
}

unsigned PropertyDescriptor::attributesWithOverride(const PropertyDescriptor& other) const
{
    unsigned mismatch = other.m_attributes ^ m_attributes;
    unsigned sharedSeen = other.m_seenAttributes & m_seenAttributes;
    unsigned newAttributes = m_attributes & defaultAttributes;
    if (sharedSeen & WritablePresent && mismatch & ReadOnly)
        newAttributes ^= ReadOnly;
    if (sharedSeen & ConfigurablePresent && mismatch & DontDelete)
        newAttributes ^= DontDelete;
    if (sharedSeen & EnumerablePresent && mismatch & DontEnum)
        newAttributes ^= DontEnum;
    if (isAccessorDescriptor() && other.isDataDescriptor())
        newAttributes |= ReadOnly;
    return newAttributes;
}

EncodedJSValue JSC_HOST_CALL objectConstructorFreeze(ExecState* exec)
{
    // 1. If Type(O) is not Object throw a TypeError exception.
    JSValue obj = exec->argument(0);
    if (!obj.isObject())
        return throwVMError(exec, createTypeError(exec, ASCIILiteral("Object.freeze can only be called on Objects.")));
    JSObject* object = asObject(obj);

    if (isJSFinalObject(object) && !hasIndexedProperties(object->structure()->indexingType())) {
        object->freeze(exec->vm());
        return JSValue::encode(obj);
    }

    // 2. For each named own property name P of O,
    PropertyNameArray properties(exec);
    object->methodTable()->getOwnPropertyNames(object, exec, properties, IncludeDontEnumProperties);
    PropertyNameArray::const_iterator end = properties.end();
    for (PropertyNameArray::const_iterator iter = properties.begin(); iter != end; ++iter) {
        // a. Let desc be the result of calling the [[GetOwnProperty]] internal method of O with P.
        PropertyDescriptor desc;
        if (!object->methodTable()->getOwnPropertyDescriptor(object, exec, *iter, desc))
            continue;
        // b. If IsDataDescriptor(desc) is true, then
        // i. If desc.[[Writable]] is true, set desc.[[Writable]] to false.
        if (desc.isDataDescriptor())
            desc.setWritable(false);
        // c. If desc.[[Configurable]] is true, set desc.[[Configurable]] to false.
        desc.setConfigurable(false);
        // d. Call the [[DefineOwnProperty]] internal method of O with P, desc, and true as arguments.
        object->methodTable()->defineOwnProperty(object, exec, *iter, desc, true);
        if (exec->hadException())
            return JSValue::encode(obj);
    }

    // 3. Set the [[Extensible]] internal property of O to false.
    object->preventExtensions(exec->vm());

    // 4. Return O.
    return JSValue::encode(obj);
}

bool JSObject::defineOwnProperty(ExecState* exec, const Identifier& propertyName, PropertyDescriptor& descriptor, bool throwException)
{
    // If we have a new property we can just put it on normally
    PropertyDescriptor current;
    if (!getOwnPropertyDescriptor(exec, propertyName, current))
        return putDescriptor(exec, this, propertyName, descriptor, descriptor.attributes(), jsUndefined());

    if (descriptor.isEmpty())
        return true;

    if (current.equalTo(descriptor))
        return true;

    // Filter out invalid changes
    if (!current.configurable()) {
        if (descriptor.configurable()) {
            if (throwException)
                throwError(exec, TypeError, "Attempting to configurable attribute of unconfigurable property.");
            return false;
        }
        if (descriptor.enumerablePresent() && descriptor.enumerable() != current.enumerable()) {
            if (throwException)
                throwError(exec, TypeError, "Attempting to change enumerable attribute of unconfigurable property.");
            return false;
        }
    }

    // A generic descriptor is simply changing the attributes of an existing property
    if (descriptor.isGenericDescriptor()) {
        if (!current.attributesEqual(descriptor)) {
            deleteProperty(exec, propertyName);
            putDescriptor(exec, this, propertyName, descriptor, current.attributesWithOverride(descriptor), current.value());
        }
        return true;
    }

    // Changing between a normal property or an accessor property
    if (descriptor.isDataDescriptor() != current.isDataDescriptor()) {
        if (!current.configurable()) {
            if (throwException)
                throwError(exec, TypeError, "Attempting to change access mechanism for an unconfigurable property.");
            return false;
        }
        deleteProperty(exec, propertyName);
        return putDescriptor(exec, this, propertyName, descriptor, current.attributesWithOverride(descriptor), current.value() ? current.value() : jsUndefined());
    }

    // Changing the value and attributes of an existing property
    if (descriptor.isDataDescriptor()) {
        if (!current.configurable()) {
            if (!current.writable() && descriptor.writable()) {
                if (throwException)
                    throwError(exec, TypeError, "Attempting to change writable attribute of unconfigurable property.");
                return false;
            }
            if (!current.writable()) {
                if (descriptor.value() || !JSValue::strictEqual(current.value(), descriptor.value())) {
                    if (throwException)
                        throwError(exec, TypeError, "Attempting to change value of a readonly property.");
                    return false;
                }
            }
        } else if (current.attributesEqual(descriptor)) {
            if (!descriptor.value())
                return true;
            PutPropertySlot slot;
            put(exec, propertyName, descriptor.value(), slot);
            if (exec->hadException())
                return false;
            return true;
        }
        deleteProperty(exec, propertyName);
        return putDescriptor(exec, this, propertyName, descriptor, current.attributesWithOverride(descriptor), current.value());
    }

    // Changing the accessor functions of an existing accessor property
    ASSERT(descriptor.isAccessorDescriptor());
    if (!current.configurable()) {
        if (descriptor.setterPresent() && !(current.setter() && JSValue::strictEqual(current.setter(), descriptor.setter()))) {
            if (throwException)
                throwError(exec, TypeError, "Attempting to change the setter of an unconfigurable property.");
            return false;
        }
        if (descriptor.getterPresent() && !(current.getter() && JSValue::strictEqual(current.getter(), descriptor.getter()))) {
            if (throwException)
                throwError(exec, TypeError, "Attempting to change the getter of an unconfigurable property.");
            return false;
        }
    }
    JSValue accessor = getDirect(propertyName);
    if (!accessor)
        return false;
    GetterSetter* getterSetter = asGetterSetter(accessor);
    if (current.attributesEqual(descriptor)) {
        if (descriptor.setter())
            getterSetter->setSetter(asObject(descriptor.setter()));
        if (descriptor.getter())
            getterSetter->setGetter(asObject(descriptor.getter()));
        return true;
    }
//.........这里部分代码省略.........