Re: Bit manipulation

[Dale Stanbrough <dale@cs.rmit.edu.au>]

Sandro Binetti wrote:

> My ADA code has, always, a little (very little) part made of "pragma
> INTERFACES" to C language, in order to manage certain Unix or Linux
> kernel capabilities (curses, for example).
> 
> So, once again, the question is the following:
> 
> IF I HAVE TO MANAGE A COMPLEX UNCOMMERCIAL DEVICE, SAY A SATELLITE BUS,
> WHY DO I HAVE TO WRITE ALL THE CODE USING ADA (IMPOSED FOR THESE REAL-
> TIME ORIENTED APPLICATIONS) AND, AT A CERTAIN MOMENT, USE LOW LEVEL
> MANIPULATION IN C LANGUAGE?

You use one argument ("i have to use Unix or Linux kernel capabilties")
to bring us to a second argument ("i have to do low level manipulation
in C").

The answer to the first argument is that you use C to call Unix routines
because either

   the ABI is a C like one
      e.g. execv does not have to be written in C, but the calling
      notations use the C language to describe it. Most of the time
      it is also written in C, but this may not always be the case.
      (is the entire POSIX compatability library for VMS written in C?).

   the routine you are calling is in C.
      You call the routines because they are there, and it's cheaper
      than rewriting them. Nothing wrong with that.


The second argument, that you -have- to use low level manipulation
in C, is not supported by any examples. I'm struggling to think up
an example for which this is the case. Could you provide an example?


Dale