[sdiy] OT (but very synthy): C question

[Tim Daugard]

> lfo.h:
>
> #ifndef PATH_TO_LFO_H_
> #define PATH_TO_LFO_H_
>
> /* We only need a forward declaration here, no need to include the

I use LFO_H_ because it's easy to remember. A declaration xxx_H_
is only defined in the header file that contains it. That way any
file that needs that function can include it. I.E.

[file LFO.h]
#ifndef LFO_H_ // has this file been called before?
 #define LFO_H_ // first time through
. . .
  // we need midi data
  #ifndef MIDI_H_
   #include "MIDI.h"
   #endif
   . . .
   now we can set up what we need that uses MIDI.h
   . . .

> full MIDI declaration */
> typedef struct MIDI MIDI;


>
> struct LFO {
> uint32_t phase_;
> };
>
> void process_lfo(LFO* lfo, MIDI* midi);
>
> #endif  /* PATH_TO_LFO_H_ */



> midi.h:
>
> #ifndef PATH_TO_MIDI_H_
> #define PATH_TO_MIDI_H_
>
> /* Includes in headers are bad, but there's no other option here
> because MIDI_MESSAGE
>  can be left as an incomplete type - we must know what it is made of to 
> know
>  the right size of the MIDI struct */
> #include "midi_message.h"
>
> /* We only need a forward declaration here, no need to include the
> full LFO declaration */
> typedef struct LFO LFO;
>
> struct MIDI {
> uint8_t running_status_;
> uint8_t data_[8];  /* whatever */
>        MIDI_MESSAGE last_message_;
> };

and then the big question is why are we processing
 midi and LFO in the MIDI header?

>
> void process_midi(MIDI* midi, LFO* lfo);

This should be at a higher level either the main.c
or a sub-level that includes both MIDI.h and LFO.h.

>
> #endif  /* PATH_TO_MIDI_H_ */


Tim Daugard
AG4GZ 30.4078N 86.6227W Alt: 12 feet above MSL
http://members.cox.net/synthfred/h_toctop.htm (Fred's online edition)