Add set of event queue composition functions

EventQueue.cpp

@@ -32,3 +32,20 @@ void EventQueue::cancel(int id) {
     return equeue_cancel(&_equeue, id);
 }
 
+void EventQueue::background(Callback<void(int)> update) {
+    _update = update;
+
+    if (_update) {
+        equeue_background(&_equeue, &Callback<void(int)>::thunk, &_update);
+    } else {
+        equeue_background(&_equeue, 0, 0);
+    }
+}
+
+void EventQueue::chain(EventQueue *target) {
+    if (target) {
+        equeue_chain(&_equeue, &target->_equeue);
+    } else {
+        equeue_chain(&_equeue, 0);
+    }
+}

EventQueue.h

@@ -80,6 +80,29 @@ class EventQueue {
      */
     void cancel(int id);
 
+    /** Background an event queue onto a single-shot timer
+     *
+     *  The provided update function will be called to indicate when the queue
+     *  should be dispatched. A negative timeout will be passed to the update
+     *  function when the timer is no longer needed. A null update function
+     *  will disable the existing timer.
+     *
+     *  @param update   Function called to indicate when the queue should be
+     *                  dispatched
+     */
+    void background(mbed::Callback<void(int)> update);
+
+    /** Chain an event queue onto another event queue
+     *
+     *  After chaining a queue to a target, calling dispatch on the target
+     *  queue will also dispatch events from this queue. The queues will use
+     *  their own buffers and events are handled independently. A null queue
+     *  as the target will unchain the queue.
+     *
+     *  @param target   Queue to chain onto
+     */
+    void chain(EventQueue *target);
+
     /** Post an event to the queue
      *
      *  @param f        Function to call on event dispatch
@@ -221,6 +244,7 @@ class EventQueue {
     void break_();
 
     struct equeue _equeue;
+    mbed::Callback<void(int)> _update;
 
     template <typename F, typename A0, typename A1, typename A2, typename A3, typename A4>
     struct Context5 {

equeue/equeue.c

@@ -39,6 +39,10 @@ int equeue_create_inplace(equeue_t *q, size_t size, void *buffer) {
     q->generation = 0;
     q->breaks = 0;
 
+    q->background.active = false;
+    q->background.update = 0;
+    q->background.timer = 0;
+
     int err;
     err = equeue_sema_create(&q->eventsema);
     if (err < 0) {
@@ -68,6 +72,10 @@ void equeue_destroy(equeue_t *q) {
         }
     }
 
+    if (q->background.update) {
+        q->background.update(q->background.timer, -1);
+    }
+
     equeue_mutex_destroy(&q->memlock);
     equeue_mutex_destroy(&q->queuelock);
     equeue_sema_destroy(&q->eventsema);
@@ -199,6 +207,11 @@ static int equeue_enqueue(equeue_t *q, struct equeue_event *e, unsigned ms) {
     *p = e;
     e->ref = p;
 
+    if ((q->background.update && q->background.active) &&
+        (q->queue == e && !e->sibling)) {
+        q->background.update(q->background.timer, ms);
+    }
+
     equeue_mutex_unlock(&q->queuelock);
 
     return id;
@@ -312,6 +325,7 @@ void equeue_break(equeue_t *q) {
 void equeue_dispatch(equeue_t *q, int ms) {
     unsigned tick = equeue_tick();
     unsigned timeout = tick + ms;
+    q->background.active = false;
 
     while (1) {
         // collect all the available events and next deadline
@@ -344,6 +358,16 @@ void equeue_dispatch(equeue_t *q, int ms) {
         if (ms >= 0) {
             deadline = equeue_tickdiff(timeout, tick);
             if (deadline <= 0) {
+                // update background timer if necessary
+                if (q->background.update) {
+                    equeue_mutex_lock(&q->queuelock);
+                    if (q->background.update && q->queue) {
+                        q->background.update(q->background.timer,
+                                equeue_tickdiff(q->queue->target, tick));
+                    }
+                    q->background.active = true;
+                    equeue_mutex_unlock(&q->queuelock);
+                }
                 return;
             }
         }
@@ -441,3 +465,54 @@ int equeue_call_every(equeue_t *q, int ms, void (*cb)(void*), void *data) {
     e->data = data;
     return equeue_post(q, ecallback_dispatch, e);
 }
+
+// backgrounding
+void equeue_background(equeue_t *q,
+        void (*update)(void *timer, int ms), void *timer) {
+    equeue_mutex_lock(&q->queuelock);
+    if (q->background.update) {
+        q->background.update(q->background.timer, -1);
+    }
+
+    q->background.update = update;
+    q->background.timer = timer;
+
+    if (q->background.update && q->queue) {
+        q->background.update(q->background.timer,
+                equeue_tickdiff(q->queue->target, equeue_tick()));
+    }
+    q->background.active = true;
+    equeue_mutex_unlock(&q->queuelock);
+}
+
+struct equeue_chain_context {
+    equeue_t *q;
+    equeue_t *target;
+    int id;
+};
+
+static void equeue_chain_dispatch(void *p) {
+    equeue_dispatch((equeue_t *)p, 0);
+}
+
+static void equeue_chain_update(void *p, int ms) {
+    struct equeue_chain_context *c = (struct equeue_chain_context *)p;
+    equeue_cancel(c->target, c->id);
+
+    if (ms >= 0) {
+        c->id = equeue_call_in(c->target, ms, equeue_chain_dispatch, c->q);
+    } else {
+        equeue_dealloc(c->target, c);
+    }
+}
+
+void equeue_chain(equeue_t *q, equeue_t *target) {
+    struct equeue_chain_context *c = equeue_alloc(q,
+            sizeof(struct equeue_chain_context));
+
+    c->q = q;
+    c->target = target;
+    c->id = 0;
+
+    equeue_background(q, equeue_chain_update, c);
+}

equeue/equeue.h

@@ -58,6 +58,12 @@ typedef struct equeue {
         unsigned char *data;
     } slab;
 
+    struct equeue_background {
+        bool active;
+        void (*update)(void *timer, int ms);
+        void *timer;
+    } background;
+
     equeue_sema_t eventsema;
     equeue_mutex_t queuelock;
     equeue_mutex_t memlock;
@@ -136,6 +142,23 @@ int equeue_post(equeue_t *queue, void (*cb)(void *), void *event);
 // stop a currently executing event
 void equeue_cancel(equeue_t *queue, int event);
 
+// Background an event queue onto a single-shot timer
+//
+// The provided update function will be called to indicate when the queue
+// should be dispatched. A negative timeout will be passed to the update
+// function when the timer is no longer needed. A null update function
+// will disable the existing timer.
+void equeue_background(equeue_t *queue,
+        void (*update)(void *timer, int ms), void *timer);
+
+// Chain an event queue onto another event queue
+//
+// After chaining a queue to a target, calling equeue_dispatch on the
+// target queue will also dispatch events from this queue. The queues
+// will use their own buffers and events are handled independently.
+// A null queue as the target will unchain this queue.
+void equeue_chain(equeue_t *queue, equeue_t *target);
+
 
 #ifdef __cplusplus
 }

equeue/tests/tests.c

@@ -479,6 +479,74 @@ void multithread_test(void) {
     equeue_destroy(&q);
 }
 
+void background_func(void *p, int ms) {
+    *(unsigned *)p = ms;
+}
+
+void background_test(void) {
+    equeue_t q;
+    int err = equeue_create(&q, 2048);
+    test_assert(!err);
+
+    int id = equeue_call_in(&q, 20, pass_func, 0);
+    test_assert(id);
+
+    unsigned ms;
+    equeue_background(&q, background_func, &ms);
+    test_assert(ms == 20);
+
+    id = equeue_call_in(&q, 10, pass_func, 0);
+    test_assert(id);
+    test_assert(ms == 10);
+
+    id = equeue_call(&q, pass_func, 0);
+    test_assert(id);
+    test_assert(ms == 0);
+
+    equeue_dispatch(&q, 0);
+    test_assert(ms == 10);
+
+    equeue_destroy(&q);
+    test_assert(ms == -1);
+}
+
+void chain_test(void) {
+    equeue_t q1;
+    int err = equeue_create(&q1, 2048);
+    test_assert(!err);
+
+    equeue_t q2;
+    err = equeue_create(&q2, 2048);
+    test_assert(!err);
+
+    equeue_chain(&q2, &q1);
+
+    int touched = 0;
+
+    int id1 = equeue_call_in(&q1, 20, simple_func, &touched);
+    int id2 = equeue_call_in(&q2, 20, simple_func, &touched);
+    test_assert(id1 && id2);
+
+    id1 = equeue_call(&q1, simple_func, &touched);
+    id2 = equeue_call(&q2, simple_func, &touched);
+    test_assert(id1 && id2);
+
+    id1 = equeue_call_in(&q1, 5, simple_func, &touched);
+    id2 = equeue_call_in(&q2, 5, simple_func, &touched);
+    test_assert(id1 && id2);
+
+    equeue_cancel(&q1, id1);
+    equeue_cancel(&q2, id2);
+
+    id1 = equeue_call_in(&q1, 10, simple_func, &touched);
+    id2 = equeue_call_in(&q2, 10, simple_func, &touched);
+    test_assert(id1 && id2);
+
+    equeue_dispatch(&q1, 30);
+
+    test_assert(touched == 6);
+}
+
 // Barrage tests
 void simple_barrage_test(int N) {
     equeue_t q;
@@ -589,6 +657,8 @@ int main() {
     test_run(period_test);
     test_run(nested_test);
     test_run(sloth_test);
+    test_run(background_test);
+    test_run(chain_test);
     test_run(multithread_test);
     test_run(simple_barrage_test, 20);
     test_run(fragmenting_barrage_test, 20);