Is there a portable alternative to C++ bitfields

Question

There are many situations (especially in low-level programming), where the binary layout of the data is important. For example: hardware/driver manipulation, network protocols,

Answer 1

C is designed for low-level bit manipulation. It's easy enough to declare a buffer of unsigned chars, and set it to any bit pattern you want. Especially if your bit strings are very short so fit into one of the integral types.

One potential problem is byte endiannness. C can't "see" this at all, but just as integers have an endianness, so too do bytes, when serialised. Another is the very small number of machines that don't use octets for bytes. C guarantees a byte shall be at least an octet, but 32 and 9 are real-world implementations. In those circumstances, you have to take a decision whether to simply ignore the uper bits (in which case naive code should work), or treat them as part of the bitstream (in which case you've got to be careful to fold CHAR_BIT into your calculations). It's also hard to test the code as you unlikely to find it easy to get your hands on a CHAR+BIT 32 machine.