当我打算实施sitn64和uint32的加法运算时，应返回结果，如AUTOSAR_SWS_EFXLibrary中的sint64类型一样。 但给出了一些条件，例如
[SWS_Efx_00415]
**C operators shall not be used for 64bit data (cast, arithmetic operators and comparison operators)**
[SWS_Efx_00416] ⌈
**64bit constants shall not be used.**
[SWS_Efx_00417]
**Direct affectation to and from a 64 bit type shall only be used through predefined functions of 64 bits library.**
[SWS_Efx_00418] ⌈
**Only the sint64 type is allowed (uint64 shall not be used)**. ⌋ ( )
[SWS_Efx_00419] ⌈
**64bit functions do not perform saturation, even for the conversion to smaller types.**
那么我们如何在不使用c运算符的情况下实现功能。