/* oskey.c - get raw keyboard input with ready testing

	Copyright 1990 Business Management Systems, Inc.
	Author: Stuart D. Gathman

	int Kgetc()	keyboard byte stream
	int Kget()	event (keycode) stream
	int Kready()	event ready

	Function call interface loosely based on "Advanced C Programming
	for Displays" by Marc J. Rochkind.

	Events are defined in keycodes.h.  Events numbered 0 - 255 are
extended ascii codes.  Most others are terminal function keys.  Exceptions:
	
	KEY_SIG		a unix signal was received
	KEY_SYNC	there are no pending keystrokes, this
			might be a good time to update the display
	KEY_MSG		a SysV message is ready, this doesn't work
			in SysV ?!?!??

	It is possible to get keycode events from multiple terminal devices.  I
didn't think this was needed any time soon, so it will require an additional
interface.

	This module is OS dependent.  The keycode recognizer (Kget) is not
and is in inkey.c.  The MSDOS version of oskey has inkey built in since
the keycode mapping is hardwired.  (Do *you* know anyone that uses a
serial terminal with MSDOS?)

	The SysV version uses stdio.  It is almost certainly already linked
in and does just what we want.  Callers can call getchar() themselves
with appropriate results.  If Kready() was last called, however, getchar()
will never wait.  Notice also the waitkey hook on our Kgetc().
*/

#include <stdio.h>
#include <fcntl.h>
#include "keyboard.h"

static FILE *curf = 0;

void Kbegin(cnt) {
  static char buf[64];
  curf = stdin;
  noecho();
  nonl();
  cmode(cnt);	/* should be 64 if ambiguous sequences */
  setvbuf(curf,buf,_IOFBF,sizeof buf);
  initkey();
}

void Kend() {
  fcntl(fileno(curf),F_SETFL,0);	/* turn off NDELAY */
  clearerr(curf);
}

void Kfile(f)
  FILE *f;
{
  curf = f;
}

/* We really aren't supposed to look at _cnt, but I'm just trying to
avoid unneccsary calls to fcntl(), OK? */

static int inKgetc = 0;

int Kready() {
  int rc;
  if (favail(curf) > 0) return 1;	/* stuff already buffered */
  if (feof(curf))
    clearerr(curf);		/* NDELAY already on */
  else				/* turn on NDELAY */
    fcntl(fileno(curf),F_SETFL,O_NDELAY);
  rc = ungetc(getc(curf),curf);
  if (inKgetc) {
    fcntl(fileno(curf),F_SETFL,0);	/* turn off NDELAY */
    clearerr(curf);
  }
  return rc != EOF;
}

/* This is the only other "magic" that is not vanilla SysV.  Waitkey is a hook
   available for programmers to arrange for routines to be called whenever
   we need to read more keyboard input.  This implementation depends
   on a particular (but almost universal) implementation of getchar().
*/

#ifdef _AIX
extern int _filbuf(FILE *);
int (*waitkey)(FILE *) = _filbuf;
#elif __linux__
static int _filbuf(FILE *f) {
  int rc = __underflow(f);
  if (rc < 0) return rc;
  return getc(curf);
}
int (*waitkey)(FILE *) = _filbuf;
#else
#error Need stdio underflow hook
#endif
int Kgetc() {
  int rc;
  if (feof(curf)) {
    fcntl(fileno(curf),F_SETFL,0);	/* turn off NDELAY */
    clearerr(curf);
  }
  inKgetc = 1;
  if (!Kready())
    rc = (*waitkey)(curf);
  else
    rc = getc(curf);
  inKgetc = 0;
  return rc;
}