/* choose.h
   %W% %G%

   Interface to routine to choose next smoker.

   Students are *not* not modify this file.

   Prepared for COP4610, Spring 1994
   --Ted Baker

   Added more comments, 3 February 1994.

 */

#define N 4                   /* the number of threads */

#define VENDOR      0
#define HAS_TOBACCO 1
#define HAS_PAPER   2
#define HAS_MATCHES 3

int exited[N];                /* exited[i] == 1 iff thread has exited */

extern int choose();                 

/* choose() 

   Will return an arbitrary value i in the range 1..3,
   but which is guaranteed to satisfy exited[i] !=0,
   if such a value exists.  Otherwise, it will return zero.

   0 signifies all smokers have exited
|  1 signifies the smoker that has tobacco has been chosen
|  2 signifies the smoker that has paper has been chosen
|  3 signifies the smoker that has matches has been chosen

 */

extern void smoker_wait_msg(int self);
/* 
|  should be called by each smoker just before it waits          
   for ingredients.                     
   The self argument should identify the particular smoker.
 */

extern void smoker_done_msg(int self);
/* should be called by each smoker when it is done smoking.
|  It should be called before the smoker signals the vendor to
|  wake up, or the order of messages may show one smoker
|  finishing after another smoker has started.
   The self argument should identify the particular smoker.
 */

extern void smoker_exit_msg(int self);
/* should be called by each smoker when it is about to exit.
   It sets exited[self] = 1, as a side-effect.
   The choose() function relies upon this.
   This prevents the vendor from causing a deadlock by putting
   out ingredients that only can be used by an exited smoker.
|  It should be called before the smoker signals the vendor to
|  wake up, or the vendor may go ahead and put out ingredients
|  for the exited smoker, causing a deadlock. 
   The self argument should identify the particular smoker.
 */


extern void vendor_service_msg(int choice);
/* should be called by the vendor when it serves ingredients.
|  It should be called before the vendor signals the smoker to
|  wake up.
   The choice argument should identify the smoker who can use
   the ingredients.
 */

extern void vendor_exit_msg();
/* should be called by the vendor when it exits
   This should only happen after all the smokers have exited,
   to avoid a deadlock.
 */