Asynchronous timer API

include/vlc_threads.h

@@ -108,6 +108,13 @@ typedef pthread_mutex_t vlc_mutex_t;
 #define VLC_STATIC_MUTEX PTHREAD_MUTEX_INITIALIZER
 typedef pthread_cond_t  vlc_cond_t;
 typedef pthread_key_t   vlc_threadvar_t;
+typedef struct vlc_timer_t vlc_timer_t;
+struct vlc_timer_t
+{
+    timer_t handle;
+    void (*func) (vlc_timer_t *, void *);
+    void *data;
+};
 
 #elif defined( WIN32 )
 typedef struct
@@ -129,6 +136,16 @@ typedef struct
 
 typedef HANDLE  vlc_cond_t;
 typedef DWORD   vlc_threadvar_t;
+typedef struct vlc_timer_t vlc_timer_t;
+struct vlc_timer_t
+{
+    HANDLE handle;
+    void (*func) (vlc_timer_t *, void *);
+    void *data;
+    unsigned overrun;
+    CRITICAL_SECTION serializer;
+    LONG volatile counter;
+};
 
 #endif
 
@@ -164,6 +181,11 @@ VLC_EXPORT( void, vlc_cancel, (vlc_thread_t) );
 VLC_EXPORT( void, vlc_join, (vlc_thread_t, void **) );
 VLC_EXPORT (void, vlc_control_cancel, (int cmd, ...));
 
+VLC_EXPORT( int, vlc_timer_create, (vlc_timer_t *, void (*) (vlc_timer_t *, void *), void *) LIBVLC_USED );
+VLC_EXPORT( void, vlc_timer_destroy, (vlc_timer_t *) );
+VLC_EXPORT( void, vlc_timer_schedule, (vlc_timer_t *, bool, mtime_t, mtime_t) );
+VLC_EXPORT( unsigned, vlc_timer_getoverrun, (const vlc_timer_t *) );
+
 #ifndef LIBVLC_USE_PTHREAD_CANCEL
 enum {
     VLC_DO_CANCEL,

src/libvlccore.sym

@@ -522,6 +522,10 @@ vlc_threadvar_create
 vlc_threadvar_delete
 vlc_threadvar_get
 vlc_threadvar_set
+vlc_timer_create
+vlc_timer_destroy
+vlc_timer_getoverrun
+vlc_timer_schedule
 vlc_ureduce
 VLC_Version
 vlc_wclosedir

src/misc/pthread.c

@@ -583,3 +583,110 @@ void vlc_control_cancel (int cmd, ...)
     (void) cmd;
     assert (0);
 }
+
+
+static void vlc_timer_do (union sigval val)
+{
+    vlc_timer_t *id = val.sival_ptr;
+    id->func (id, id->data);
+}
+
+/**
+ * Initializes an asynchronous timer.
+ * @warning Asynchronous timers are processed from an unspecified thread, and
+ * a timer is only serialized against itself.
+ *
+ * @param id pointer to timer to be initialized
+ * @param func function that the timer will call
+ * @param data parameter for the timer function
+ * @return 0 on success, a system error code otherwise.
+ */
+int vlc_timer_create (vlc_timer_t *id, void (*func) (vlc_timer_t *, void *),
+                      void *data)
+{
+    struct sigevent ev;
+
+    memset (&ev, 0, sizeof (ev));
+    ev.sigev_notify = SIGEV_THREAD;
+    ev.sigev_value.sival_ptr = id;
+    ev.sigev_notify_function = vlc_timer_do;
+    ev.sigev_notify_attributes = NULL;
+    id->func = func;
+    id->data = data;
+
+    if (timer_create (CLOCK_MONOTONIC, &ev, &id->handle))
+        return errno;
+    return 0;
+}
+
+/**
+ * Destroys an initialized timer. If needed, the timer is first disarmed.
+ * This function is undefined if the specified timer is not initialized.
+ *
+ * @warning This function <b>must</b> be called before the timer data can be
+ * freed and before the timer callback function can be unloaded.
+ *
+ * @param timer to destroy
+ */
+void vlc_timer_destroy (vlc_timer_t *id)
+{
+    int val = timer_delete (id->handle);
+    VLC_THREAD_ASSERT ("deleting timer");
+}
+
+/**
+ * Arm or disarm an initialized timer.
+ * This functions overrides any previous call to itself.
+ *
+ * @note A timer can fire later than requested due to system scheduling
+ * limitations. An interval timer can fail to trigger sometimes, either because
+ * the system is busy or suspended, or because a previous iteration of the
+ * timer is still running. See also vlc_timer_getoverrun().
+ *
+ * @param id initialized timer pointer
+ * @param absolute the timer value origin is the same as mdate() if true,
+ *                 the timer value is relative to now if false.
+ * @param value zero to disarm the timer, otherwise the initial time to wait
+ *              before firing the timer.
+ * @param interval zero to fire the timer just once, otherwise the timer
+ *                 repetition interval.
+ */
+void vlc_timer_schedule (vlc_timer_t *id, bool absolute,
+                         mtime_t value, mtime_t interval)
+{
+    lldiv_t vad = lldiv (value, CLOCK_FREQ);
+    lldiv_t itd = lldiv (interval, CLOCK_FREQ);
+    struct itimerspec it = {
+        .it_interval = {
+            .tv_sec = itd.quot,
+            .tv_nsec = (1000000000 / CLOCK_FREQ) * itd.rem,
+        },
+        .it_value = {
+            .tv_sec = vad.quot,
+            .tv_nsec = (1000000000 / CLOCK_FREQ) * vad.rem,
+        },
+    };
+    int flags = absolute ? TIMER_ABSTIME : 0;
+
+    int val = timer_settime (id->handle, flags, &it, NULL);
+    VLC_THREAD_ASSERT ("scheduling timer");
+}
+
+/**
+ * @param id initialized timer pointer
+ * @return the timer overrun counter, i.e. the number of times that the timer
+ * should have run but did not since the last actual run. If all is well, this
+ * is zero.
+ */
+unsigned vlc_timer_getoverrun (const vlc_timer_t *id)
+{
+    int val = timer_getoverrun (id->handle);
+#ifndef NDEBUG
+    if (val == -1)
+    {
+        val = errno;
+        VLC_THREAD_ASSERT ("fetching timer overrun counter");
+    }
+#endif
+    return val;
+}

src/misc/w32thread.c

@@ -510,3 +510,63 @@ void vlc_control_cancel (int cmd, ...)
     }
     va_end (ap);
 }
+
+
+/*** Timers ***/
+static void CALLBACK vlc_timer_do (void *val, BOOLEAN timeout)
+{
+    vlc_timer_t *id = val;
+
+    assert (timeout);
+    if (TryEnterCriticalSection (&id->serializer))
+    {
+        id->overrun = InterlockedExchange (&id->counter, 0);
+        id->func (id, id->data);
+        LeaveCriticalSection (&id->serializer);
+    }
+    else /* Overrun */
+        InterlockedIncrement (&id->counter);
+}
+
+int vlc_timer_create (vlc_timer_t *id, void (*func) (vlc_timer_t *, void *),
+                      void *data)
+{
+    id->func = func;
+    id->data = data;
+    id->overrun = 0;
+    id->handle = INVALID_HANDLE_VALUE;
+    InitializeCriticalSection (&id->serializer);
+    return 0;
+}
+
+void vlc_timer_destroy (vlc_timer_t *id)
+{
+    if (id->handle != INVALID_HANDLE_VALUE)
+        DeleteTimerQueueTimer (NULL, id->handle, NULL);
+    DeleteCriticalSection (&id->serializer);
+}
+
+void vlc_timer_schedule (vlc_timer_t *id, bool absolute,
+                         mtime_t value, mtime_t interval)
+{
+    if (id->handle != INVALID_HANDLE_VALUE)
+    {
+        DeleteTimerQueueTimer (NULL, id->handle, NULL);
+        id->handle = INVALID_HANDLE_VALUE;
+    }
+    if (value == 0)
+        return; /* Disarm */
+
+    if (absolute)
+        value -= mdate ();
+    value = (value + 999) / 1000;
+    interval = (interval + 999) / 1000;
+    if (!CreateTimerQueueTimer (&id->handle, NULL, vlc_timer_do, id, value,
+                                interval, WT_EXECUTEDEFAULT))
+        abort ();
+}
+
+unsigned vlc_timer_getoverrun (const vlc_timer_t *id)
+{
+    return id->overrun;
+}