#ifndef _TIMER_H_
#define _TIMER_H_

/*32:10 format*/
extern uint64_t tsc;

/*Timers are based on the CPU Time Stamp Counter. Timer timestamps are in a
  32:32 fixed point format, with the integer part compared against the TSC. The
  fractional part is used when advancing the timestamp to ensure a more accurate
  period.

  When a timer callback is called, the timer has been disabled. If the timer is
  to repeat, the callback must call timer_advance_u64().*/
typedef struct emu_timer_t
{
	uint32_t ts_integer;
	uint32_t ts_frac;
	int enabled;

	void (*callback)(void *p);
	void *p;

	struct emu_timer_t *prev, *next;
} emu_timer_t;

/*Timestamp of nearest enabled timer. CPU emulation must call timer_process()
  when TSC matches or exceeds this.*/
extern uint32_t timer_target;

/*Enable timer, without updating timestamp*/
void timer_enable(emu_timer_t *timer);
/*Disable timer*/
void timer_disable(emu_timer_t *timer);

/*Process any pending timers*/
void timer_process();

/*Reset timer system*/
void timer_reset();

/*Add new timer. If start_timer is set, timer will be enabled with a zero
  timestamp - this is useful for permanently enabled timers*/
void timer_add(emu_timer_t *timer, void (*callback)(void *p), void *p, int start_timer);

/*1us in 32:32 format*/
extern uint64_t TIMER_USEC;

/*True if timer a expires before timer b*/
#define TIMER_LESS_THAN(a, b) ((int32_t)((a)->ts_integer - (b)->ts_integer) <= 0)
/*True if timer a expires before 32 bit integer timestamp b*/
#define TIMER_LESS_THAN_VAL(a, b) ((int32_t)((a)->ts_integer - (b)) <= 0)
/*True if 32 bit integer timestamp a expires before 32 bit integer timestamp b*/
#define TIMER_VAL_LESS_THAN_VAL(a, b) ((int32_t)((a) - (b)) <= 0)
#define TIMER_VAL_LESS_THAN_VAL_64(a, b) ((int64_t)((a) - (b)) <= 0)
#define TIMER_VAL_LESS_THAN_NE_VAL(a, b) ((int32_t)((a) - (b)) < 0)
#define TIMER_VAL_LESS_THAN_NE_VAL_64(a, b) ((int64_t)((a) - (b)) < 0)

/*Advance timer by delay, specified in 32:32 format. This should be used to
  resume a recurring timer in a callback routine*/
static inline void timer_advance_u64(emu_timer_t *timer, uint64_t delay)
{
	uint32_t int_delay = delay >> 32;
	uint32_t frac_delay = delay & 0xffffffff;

	if ((frac_delay + timer->ts_frac) < frac_delay)
		timer->ts_integer++;
	timer->ts_frac += frac_delay;
	timer->ts_integer += int_delay;

	timer_enable(timer);
}

/*Set a timer to the given delay, specified in 32:32 format. This should be used
  when starting a timer*/
static inline void timer_set_delay_u64(emu_timer_t *timer, uint64_t delay)
{
	uint32_t int_delay = delay >> 32;
	uint32_t frac_delay = delay & 0xffffffff;

	timer->ts_frac = frac_delay;
	timer->ts_integer = int_delay + (uint32_t)(tsc >> 32);

	timer_enable(timer);
}

static inline uint64_t timer_get_ts(emu_timer_t *timer)
{
	return ((uint64_t)timer->ts_integer << 32) | timer->ts_frac;
}

/*True if timer currently enabled*/
static inline int timer_is_enabled(emu_timer_t *timer)
{
	return timer->enabled;
}

/*Return integer timestamp of timer*/
static inline uint32_t timer_get_ts_int(emu_timer_t *timer)
{
	return timer->ts_integer;
}

/*Return remaining time before timer expires, in us. If the timer has already
  expired then return 0*/
static inline uint32_t timer_get_remaining_us(emu_timer_t *timer)
{
	if (timer->enabled)
	{
		int64_t remaining = (((uint64_t)timer->ts_integer << 32) | timer->ts_frac) - tsc;

		if (remaining < 0)
			return 0;
		return remaining / TIMER_USEC;
	}

	return 0;
}

/*Return remaining time before timer expires, in 32:32 timestamp format. If the
  timer has already expired then return 0*/
static inline uint64_t timer_get_remaining_u64(emu_timer_t *timer)
{
	if (timer->enabled)
	{
		int64_t remaining = (((uint64_t)timer->ts_integer << 32) | timer->ts_frac) - tsc;

		if (remaining < 0)
			return 0;
		return remaining;
	}

	return 0;
}

/*Set timer callback function*/
static inline void timer_set_callback(emu_timer_t *timer, void (*callback)(void *p))
{
	timer->callback = callback;
}
/*Set timer private data*/
static inline void timer_set_p(emu_timer_t *timer, void *p)
{
	timer->p = p;
}
#endif /*_TIMER_H_*/
