If you're worrying about the endianness of your processor, your code is somehow accessing memory from 'outside' as anything other than a char*, which is already

If you're worrying about the endianness of your processor, your code is somehow accessing memory from 'outside' as anything other than a char*, which is already thin ice as far as C and C++ are concerned. You should have a parse_<whatever>_le and/or parse_<whatever>_be function to convert from that byte stream into your native types, that only cares about the _endianness of the data_ (and they can be implemented without caring about your processor endianness as well). Then you don't need to worry about the processor you're running on at all. There's more significant and subtle processor quirks than endianness to worry about if you're trying to write portable code (namely, memory model and alignment requirements).