Re: adasockets and adatypes

[Simon Wright <simon@pushface.org>]

Peter Dulimov <pedu@eraseme.systems.saab.se> writes:

> Also, what about the efficiency consideration?  The compiler
> generally chooses the best representation that it can to get
> alignment right for complicated data types, and if you go specifying
> every bit's position, you are likely to introduce more fix-up
> delays.  When I have done this (specifying bit patterns for socket
> comms with C programs etc), I have had a type defined for "on the
> wire" where the representation is specified, and another equivalent
> type for internal usage where I let the compiler choose the
> representation.  The conversion from one type to another is the last
> thing that happens {before hitting | after leaving} the wire.

Yes.

One Ada possibility here is to specify a type without representation
clauses and then create a wire format subtype with representation
clauses (in a local declarative part). You can make the choice of big-
or little-endian depending on the value of System.Default_Bit_Order[1],
which with any luck will be optimised at compile time so only one
branch is compiled.

[1] Purists would argue that this isn't the same as byte order, though
it always has been for me.