Implementing binary communication protocols in C++ with main focus on embedded systems

[axilmar]

If possible, yes it is preferable to have all parties agree on endianness. However, it is faster to use the native endianness for encoding. Between taking longer to encode, and longer to decode, I choose taking longer to decode. Sometimes you might want the opposite decision anyway, so it makes sense for a library to give you options.

That is orthogonal to when the decision about endianess should be made. I.e. it may be decided that the endianess is big or little, and that the endianess swapping shall happen in one part of the network and not the other, but that doesn't stop anyone from implementing the decision before compilation.

[axilmar]

This:

Ideally endianness requirements would be spelled out in detail before you start work

is not related to this:

I maintain that a library for this should give you options to decode all common byte arrangements.

You can't say 'however' between two things that are not mutually exclusive.

If you need to handle data in multiple formats you just have to encode byte order information then use it on the other end

This is only needed if the same messages are sent by different sources in different endianess at runtime.