[CCC DEV] REAL32 to FFI

[Adam Sampson]

Matt Jadud <jadudm at gmail.com> writes:

> Another question: REAL32s on the Arduino are, I assume, not going to
> pass through the FFI nicely. At least, I assume they aren't.

That's probably a safe assumption, but I've not tried it. What it
"ought" to do for types larger than the word size is what it does for
VAL INT64 arguments on a 32-bit platform: pass a pointer instead.
You never know, it might even work. ;-)

> Should I shift them into a pair of INT16s, pass them through, and
> reconstitute them on the other side?

Yes, retyping it into an array should work; something like:

(extern) PROC ffi.garble (VAL [2]INT16 value)

PROC garble (VAL REAL32 value)
  VAL [2]INT16 ivalue RETYPES value:
  ffi.garble (ivalue)
:

...

void _ffi_garble (word *w) {
  float value = *((float *) w[1]);
  ...
}

(Did we have endianness problems in the past?)

-- 
Adam Sampson <ats at offog.org>                         <http://offog.org/>