Group PJ_TIMER

group PJ_TIMER

The timer scheduling implementation here is based on ACE library’s ACE_Timer_Heap, with only little modification to suit our library’s style (I even left most of the comments in the original source).

To quote the original quote in ACE_Timer_Heap_T class:

 This implementation uses a heap-based callout queue of
 absolute times.  Therefore, in the average and worst case,
 scheduling, canceling, and expiring timers is O(log N) (where
 N is the total number of timers).  In addition, we can also
 preallocate as many \a ACE_Timer_Nodes as there are slots in
 the heap.  This allows us to completely remove the need for
 dynamic memory allocation, which is important for real-time
 systems.

You can find the fine ACE library at: http://www.cs.wustl.edu/~schmidt/ACE.html

Examples

For some examples on how to use the timer heap, please see the link below.

Timer test: pjlib/src/pjlib-test/timer.c

Typedefs

typedef int pj_timer_id_t: The type for internal timer ID.

typedef void pj_timer_heap_callback(pj_timer_heap_t *timer_heap, struct pj_timer_entry *entry)

The type of callback function to be called by timer scheduler when a timer has expired.

Param timer_heap:: The timer heap.
Param entry:: Timer entry which timer’s has expired.

Functions

pj_size_t pj_timer_heap_mem_size(pj_size_t count)

Calculate memory size required to create a timer heap.

Parameters:: count – Number of timer entries to be supported.
Returns:: Memory size requirement in bytes.

pj_status_t pj_timer_heap_create(pj_pool_t *pool, pj_size_t count, pj_timer_heap_t **ht)

Create a timer heap.

Parameters:

pool – The pool where allocations in the timer heap will be allocated. The timer heap will dynamicly allocate more storate from the pool if the number of timer entries registered is more than the size originally requested when calling this function.
count – The maximum number of timer entries to be supported initially. If the application registers more entries during runtime, then the timer heap will resize.
ht – Pointer to receive the created timer heap.

Returns:

PJ_SUCCESS, or the appropriate error code.

void pj_timer_heap_destroy(pj_timer_heap_t *ht)

Destroy the timer heap.

Parameters:: ht – The timer heap.

void pj_timer_heap_set_lock(pj_timer_heap_t *ht, pj_lock_t *lock, pj_bool_t auto_del)

Set lock object to be used by the timer heap. By default, the timer heap uses dummy synchronization.

Parameters:

ht – The timer heap.
lock – The lock object to be used for synchronization.
auto_del – If nonzero, the lock object will be destroyed when the timer heap is destroyed.

unsigned pj_timer_heap_set_max_timed_out_per_poll(pj_timer_heap_t *ht, unsigned count)

Set maximum number of timed out entries to process in a single poll.

Parameters:

ht – The timer heap.
count – Number of entries.

Returns:

The old number.

pj_timer_entry *pj_timer_entry_init(pj_timer_entry *entry, int id, void *user_data, pj_timer_heap_callback *cb)

Initialize a timer entry. Application should call this function at least once before scheduling the entry to the timer heap, to properly initialize the timer entry.

Parameters:

entry – The timer entry to be initialized.
id – Arbitrary ID assigned by the user/owner of this entry. Applications can use this ID to distinguish multiple timer entries that share the same callback and user_data.
user_data – User data to be associated with this entry. Applications normally will put the instance of object that owns the timer entry in this field.
cb – Callback function to be called when the timer elapses.

Returns:

The timer entry itself.

pj_bool_t pj_timer_entry_running(pj_timer_entry *entry)

Queries whether a timer entry is currently running.

Parameters:: entry – The timer entry to query.
Returns:: PJ_TRUE if the timer is running. PJ_FALSE if not.

pj_status_t pj_timer_heap_schedule(pj_timer_heap_t *ht, pj_timer_entry *entry, const pj_time_val *delay)

Schedule a timer entry which will expire AFTER the specified delay.

Parameters:

ht – The timer heap.
entry – The entry to be registered.
delay – The interval to expire.

Returns:

PJ_SUCCESS, or the appropriate error code.

pj_status_t pj_timer_heap_schedule_w_grp_lock(pj_timer_heap_t *ht, pj_timer_entry *entry, const pj_time_val *delay, int id_val, pj_grp_lock_t *grp_lock)

Schedule a timer entry which will expire AFTER the specified delay, and increment the reference counter of the group lock while the timer entry is active. The group lock reference counter will automatically be released after the timer callback is called or when the timer is cancelled.

Parameters:

ht – The timer heap.
entry – The entry to be registered.
delay – The interval to expire.
id_val – The value to be set to the “id” field of the timer entry once the timer is scheduled.
grp_lock – The group lock.

Returns:

PJ_SUCCESS, or the appropriate error code.

int pj_timer_heap_cancel(pj_timer_heap_t *ht, pj_timer_entry *entry)

Cancel a previously registered timer. This will also decrement the reference counter of the group lock associated with the timer entry, if the entry was scheduled with one.

Parameters:

ht – The timer heap.
entry – The entry to be cancelled.

Returns:

The number of timer cancelled, which should be one if the entry has really been registered, or zero if no timer was cancelled.

int pj_timer_heap_cancel_if_active(pj_timer_heap_t *ht, pj_timer_entry *entry, int id_val)

Cancel only if the previously registered timer is active. This will also decrement the reference counter of the group lock associated with the timer entry, if the entry was scheduled with one. In any case, set the “id” to the specified value.

Parameters:

ht – The timer heap.
entry – The entry to be cancelled.
id_val – Value to be set to “id”

Returns:

The number of timer cancelled, which should be one if the entry has really been registered, or zero if no timer was cancelled.

pj_size_t pj_timer_heap_count(pj_timer_heap_t *ht)

Get the number of timer entries.

Parameters:: ht – The timer heap.
Returns:: The number of timer entries.

pj_status_t pj_timer_heap_earliest_time(pj_timer_heap_t *ht, pj_time_val *timeval)

Get the earliest time registered in the timer heap. The timer heap MUST have at least one timer being scheduled (application should use pj_timer_heap_count() before calling this function).

Parameters:

ht – The timer heap.
timeval – The time deadline of the earliest timer entry.

Returns:

PJ_SUCCESS, or PJ_ENOTFOUND if no entry is scheduled.

unsigned pj_timer_heap_poll(pj_timer_heap_t *ht, pj_time_val *next_delay)

Poll the timer heap, check for expired timers and call the callback for each of the expired timers.

Note: polling the timer heap is not necessary in Symbian. Please see Symbian OS Specific for more info.

Parameters:

ht – The timer heap.
next_delay – If this parameter is not NULL, it will be filled up with the time delay until the next timer elapsed, or PJ_MAXINT32 in the sec part if no entry exist.

Returns:

The number of timers expired.

struct pj_timer_entry

#include <timer.h>

This structure represents an entry to the timer.

Public Members

void *user_data: User data to be associated with this entry. Applications normally will put the instance of object that owns the timer entry in this field.

int id: Arbitrary ID assigned by the user/owner of this entry. Applications can use this ID to distinguish multiple timer entries that share the same callback and user_data.

pj_timer_heap_callback *cb: Callback to be called when the timer expires.

pj_timer_id_t _timer_id: Internal unique timer ID, which is assigned by the timer heap. Positive values indicate that the timer entry is running, while -1 means that it’s not. Any other value may indicate that it hasn’t been properly initialised or is in a bad state. Application should not touch this ID.

pj_time_val _timer_value: The future time when the timer expires, which the value is updated by timer heap when the timer is scheduled.

pj_grp_lock_t *_grp_lock: Internal: the group lock used by this entry, set when pj_timer_heap_schedule_w_lock() is used.