ext_mongo.php (extract)

<?hh
namespace MongoDB\Driver;

<<__NativeData("MongoDBDriverReadPreference")>>
final class ReadPreference {
    <<__Native>>
    private function _setReadPreference(int $readPreference): void;

    <<__Native>>
    private function _setReadPreferenceTags(array $tagSets): void;

    public function __construct(int $readPreference, mixed $tagSets = null)
    {
        if ($tagSets !== NULL && Utils::mustBeArrayOrObject('parameter 2', $tagSets)) {
            return;
        }

        switch ($readPreference) {
            case ReadPreference::RP_PRIMARY:
            case ReadPreference::RP_PRIMARY_PREFERRED:
            case ReadPreference::RP_SECONDARY:
            case ReadPreference::RP_SECONDARY_PREFERRED:
            case ReadPreference::RP_NEAREST:
                // calling into Native
                $this->_setReadPreference($readPreference);

                if ($tagSets) {
                    // calling into Native, might throw exception
                    $this->_setReadPreferenceTags($tagSets);
                }

                break;

            default:
                Utils::throwHippoException(Utils::ERROR_INVALID_ARGUMENT, "Invalid ReadPreference");
                break;
        }
    }
}
src/MongoDB/Driver/Manager (extract)

void HHVM_METHOD(MongoDBDriverReadPreference, _setReadPreference, int readPreference)
{
    MongoDBDriverReadPreferenceData* data = Native::data<MongoDBDriverReadPreferenceData>(this_);

    data->m_read_preference = mongoc_read_prefs_new((mongoc_read_mode_t) readPreference);
}