Path: utzoo!utgpu!water!watmath!clyde!att!osu-cis!tut.cis.ohio-state.edu!bloom-beacon!apple!bionet!agate!ucbvax!ucsd!telesoft!jjh
From: jjh@telesoft.UUCP (Jim Hayes @dance)
Newsgroups: comp.unix.wizards
Subject: RESULTS: How to write keypressed()?
Message-ID: <317@telesoft.UUCP>
Date: 4 Oct 88 18:09:42 GMT
Organization: TeleSoft Inc., San Diego, CA
Lines: 47

My thanks to everyone who responded to my request for suggestions on testing
for available characters in the keyboard buffer. After much experimentation,
I finally got a function that seems to work:

/*============================================================================*/

jmp_buf program_state;

timeout_handler() {
  longjmp(program_state, 1);
}

short keypressed() {
/* Returns 1 if there's a character in the keyboard input buffer, 0 otherwise */

  int a_char;

  if ( isatty( fileno(stdin) ) == 1 ) {
    signal(SIGALRM, timeout_handler);
    if ( setjmp(program_state) == 1 ) {
      return (0);
    }
    else {
      alarm(1);
      a_char = getc(stdin);
      alarm(0);
      ungetc(a_char, stdin);
      return (1);
    }
  }
  else {
    return (0);
  }
}

/*============================================================================*/

My special thanks to David Barto for the basic algorithm, and to everyone who
pointed out that I shouldn't be mixing read() and ungetc().
--Jim

------------------------------------------------------------------------------
"'Happiness' is being famous for your financial |
 ability to indulge in every kind of excess."   |   Jim Hayes
"I suppose that's *one* way to define it."      |
"The part I think I'd like best is crushing     |   ...!ucsd!telesoft!jjh
 people who get in my way."                     |