/* Software timers
 * There is one of these structures for each simulated timer.
 * Whenever the timer is running, it is on a doubly-linked list
 * pointed to by "timers" so that the (hardware) timer interrupt
 * can quickly run through the list and change counts and states.
 * Stopping a timer or letting it expire causes it to be removed
 * from the list; starting a timer puts it on the list.
 */
struct timer {
	struct timer *next;	/* Doubly-linked-list pointers */
	struct timer *prev;
	int32 start;		/* Period of counter (load value) */
	int32 count;		/* Ticks to go until expiration */
	void (*func)();		/* Function to call at expiration */
	char *arg;		/* Arg to pass function */
	char state;		/* Timer state */
#define	TIMER_STOP	0
#define	TIMER_RUN	1
#define	TIMER_EXPIRE	2
};
#define	NULLTIMER	(struct timer *)0
#define	MAX_TIME	(int32)2147483647L	/* Max long integer */
#ifdef ATARI_ST
# define MSPTICK 	100		/* Atari: 10 real ticks per second */
#endif
#ifdef MSDOS
# define MSPTICK 	55		/* Milliseconds per tick */
#endif
#ifdef UNIX
# define MSPTICK	20		/* assuming HZ=50 */
#endif
#ifndef MSPTICK
# define MSPTICK 	1000		/* default value 1 sec/tick */
#endif

/* Macros to convert between ticks and (milli)seconds */
#define TICK2MS(v)	((int32)(v) * MSPTICK)
#define MS2TICK(v)	(((int32)(v) + ((int32) MSPTICK / 2)) / MSPTICK)
#define TICK2SEC(v)	((((int32)(v) * MSPTICK) + 500L) / 1000L)
#define SEC2TICK(v)	((int32)(v) * 1000L / MSPTICK)

/* Useful user macros that hide the timer structure internals */
#define	set_timer(t,x)	(((t)->start) = (x)/MSPTICK)
#define	dur_timer(t)	((t)->start)
#define	read_timer(t)	((t)->count)
#define	run_timer(t)	((t)->state == TIMER_RUN)