> On May 20, 2016, at 12:54 PM, Joe Groff via swift-users > <swift-users@swift.org> wrote: > > >> On May 20, 2016, at 7:33 AM, Ken Burgett via swift-users >> <swift-users@swift.org> wrote: >> >> I have been told that the in-memory layout of a Swift struct is 'undefined', >> so the C style of aliasing an array over a struct and iterating across the >> struct is a definite no-no. Not surprising, since aliasing violates all >> type-safe rules. >> >> So, if you have this situation, you must address it on a case-by-case basis. >> In my case, converting a hash algorithm from C to Swift, the required C >> struct morphs into a Swift class, with a member function 'as_C_byte_array' >> which answers an array of the required form. Internally, this function will >> shift and mask class attributes in order to build the necessary result. > > That's not necessary. You can leave the struct defined in C and import it > into Swift. Swift will respect C's layout.
Any thought on introducing an attribute or something into the “generated header” for these C imports to make this more clear? The same syntax could be used in the future if / when Swift supports more control over layout. > > -Joe > >> Ugly, but I must preserve the semantics exactly if I hope to generate the >> exact same hash as the C version. >> >> -- >> Ken Burgett >> Principal Software Engineer >> Email: k...@iotone.io >> Office: 530.693.4449 >> Mobile: 831.332.6846 >> URL: www.iotone.co >> _______________________________________________ >> swift-users mailing list >> swift-users@swift.org >> https://lists.swift.org/mailman/listinfo/swift-users > > _______________________________________________ > swift-users mailing list > swift-users@swift.org > https://lists.swift.org/mailman/listinfo/swift-users _______________________________________________ swift-users mailing list swift-users@swift.org https://lists.swift.org/mailman/listinfo/swift-users
