gw-timer.h

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/*
 * gw-timer.h - interface to timers and timer sets.
 *
 * Timers can be set to elapse after a specified number of seconds
 * (the "interval").  They can be stopped before elapsing, and the
 * interval can be changed.
 *
 * An "output list" is defined for each timer.  When it elapses, an
 * event is generated on this list.  The event may be removed from
 * the output list if the timer is destroyed or extended before the
 * event is consumed.
 *
 * The event to use when a timer elapses is provided by the caller.
 * The timer module will "own" it, and be responsible for deallocation.
 * This will be true until the event has been consumed from the output
 * list (at which point it is owned by the consuming thread).
 * While the event is on the output list, it is in a gray area, because
 * the timer module might still take it back.  This won't be a problem
 * as long as you access the event only by consuming it.
 *
 * Timers work best if the thread that manipulates the timer (the
 * "calling thread") is the same thread that consumes the output list.
 * This way, it can be guaranteed that the calling thread will not
 * see a timer elapse after being destroyed, or while being extended,
 * because the elapse event will be deleted during such an operation.
 *
 * The timer_* functions have been renamed to gwtimer_* to avoid
 * a name conflict on Solaris systems.
 */

#ifndef GW_TIMER_H
#define GW_TIMER_H

#include "gwlib/gwlib.h"

typedef struct Timer Timer;
typedef struct Timerset Timerset;


Timerset *gw_timerset_create(void);
void gw_timerset_destroy(Timerset *set);
void gw_timerset_elapsed_destroy(Timerset *set);
long gw_timerset_count(Timerset *set);


/*
 * Create a timer and tell it to use the specified output list or
 * callback function when it elapses.
 * Do not start it yet.  Return the new timer.
 */
Timer *gw_timer_create(Timerset *set, List *outputlist, void (*callback) (void*));

/*
 * Destroy this timer and free its resources.  Stop it first, if needed.
 *
 * (The _elapsed_ variant assumes that there can't be any further events
 * within the output list for this timer, which reduces the need to
 * traverse the output list and delete the corresponding events.)
 *
 * (The _destroy_cb variant MUST be used for callback'ed time events, as
 * it will not try to lock the Timerset again, being already locked.)
 */
void gw_timer_destroy(Timer *timer);
void gw_timer_elapsed_destroy(Timer *timer);
void gw_timer_elapsed_destroy_cb(Timer *timer);


/*
 * Make the timer elapse after 'interval' seconds, at which time it
 * will push event 'event' on the output list defined for its timer set.
 * - If the timer was already running, these parameters will override
 *   its old settings.
 * - If the timer has already elapsed, try to remove its event from
 *   the output list.
 * If this is not the first time the timer was started, the event
 * pointer is allowed to be NULL.  In that case the event pointer
 * from the previous call to timer_start for this timer is re-used.
 * NOTE: Each timer must have a unique event pointer.  The caller must
 * create the event, and passes control of it to the timer module with
 * this call.
 *
 * (The _elapsed_ variant assumes that there can't be any further events
 * within the output list for this timer, which reduces the need to
 * traverse the output list and delete the corresponding events.)
 */
void gw_timer_start(Timer *timer, int interval, void *data);
void gw_timer_elapsed_start(Timer *timer, int interval, void *data);
void gw_timer_elapsed_start_cb(Timer *timer, int interval, void *data);


/*
 * Stop this timer.  If it has already elapsed, try to remove its
 * event from the output list.
 *
 * (The _elapsed_ variant assumes that there can't be any further events
 * within the output list for this timer, which reduces the need to
 * traverse the output list and delete the corresponding events.)
 *
 * (The _destroy_cb variant MUST be used for callback'ed time events, as
 * it will not try to lock the Timerset again, being already locked.)
 */
void gw_timer_stop(Timer *timer);
void gw_timer_elapsed_stop(Timer *timer);
void gw_timer_elapsed_stop_cb(Timer *timer);

/*
 * Stop all active timers, elapsed or not, and return them via the
 * returned List result. They are not destroyed yet.
 */
List *gw_timer_break(Timerset *set);

/*
 * Return the void* pointer to the associated data of the Timer.
 */
void *gw_timer_data(Timer *timer);

#endif