stm32/softtimer: Change linear linked list to a pairing heap.

ports/stm32/machine_timer.c

@@ -77,7 +77,7 @@ STATIC mp_obj_t machine_timer_init_helper(machine_timer_obj_t *self, size_t n_ar
 
 STATIC mp_obj_t machine_timer_make_new(const mp_obj_type_t *type, size_t n_args, size_t n_kw, const mp_obj_t *args) {
     machine_timer_obj_t *self = m_new_obj(machine_timer_obj_t);
-    self->base.type = &machine_timer_type;
+    self->pairheap.base.type = &machine_timer_type;
 
     // Get timer id (only soft timer (-1) supported at the moment)
     mp_int_t id = -1;

ports/stm32/mpconfigport.h

@@ -281,7 +281,7 @@ struct _mp_bluetooth_nimble_root_pointers_t;
     \
     mp_obj_t pyb_extint_callback[PYB_EXTI_NUM_VECTORS]; \
     \
-    struct _soft_timer_entry_t *soft_timer_head; \
+    struct _soft_timer_entry_t *soft_timer_heap; \
     \
     /* pointers to all Timer objects (if they have been created) */ \
     struct _pyb_timer_obj_t *pyb_timer_obj_all[MICROPY_HW_MAX_TIMER]; \

ports/stm32/softtimer.c

@@ -37,7 +37,13 @@ extern __IO uint32_t uwTick;
 volatile uint32_t soft_timer_next;
 
 void soft_timer_deinit(void) {
-    MP_STATE_PORT(soft_timer_head) = NULL;
+    MP_STATE_PORT(soft_timer_heap) = NULL;
+}
+
+STATIC int soft_timer_lt(mp_pairheap_t *n1, mp_pairheap_t *n2) {
+    soft_timer_entry_t *e1 = (soft_timer_entry_t*)n1;
+    soft_timer_entry_t *e2 = (soft_timer_entry_t*)n2;
+    return TICKS_DIFF(e1->expiry_ms, e2->expiry_ms) < 0;
 }
 
 STATIC void soft_timer_schedule_systick(uint32_t ticks_ms) {
@@ -54,59 +60,38 @@ STATIC void soft_timer_schedule_systick(uint32_t ticks_ms) {
 // Must be executed at IRQ_PRI_PENDSV
 void soft_timer_handler(void) {
     uint32_t ticks_ms = uwTick;
-    soft_timer_entry_t *head = MP_STATE_PORT(soft_timer_head);
-    while (head != NULL && TICKS_DIFF(head->expiry_ms, ticks_ms) <= 0) {
-        mp_sched_schedule(head->callback, MP_OBJ_FROM_PTR(head));
-        if (head->mode == SOFT_TIMER_MODE_PERIODIC) {
-            head->expiry_ms += head->delta_ms;
-            // Shift this node along to its new position
-            soft_timer_entry_t *cur = head;
-            while (cur->next != NULL && TICKS_DIFF(head->expiry_ms, cur->next->expiry_ms) >= 0) {
-                cur = cur->next;
-            }
-            if (cur != head) {
-                soft_timer_entry_t *next = head->next;
-                head->next = cur->next;
-                cur->next = head;
-                head = next;
-            }
-        } else {
-            head = head->next;
+    soft_timer_entry_t *heap = MP_STATE_PORT(soft_timer_heap);
+    while (heap != NULL && TICKS_DIFF(heap->expiry_ms, ticks_ms) <= 0) {
+        soft_timer_entry_t *entry = heap;
+        heap = (soft_timer_entry_t*)mp_pairheap_pop(soft_timer_lt, &heap->pairheap);
+        mp_sched_schedule(entry->callback, MP_OBJ_FROM_PTR(entry));
+        if (entry->mode == SOFT_TIMER_MODE_PERIODIC) {
+            entry->expiry_ms += entry->delta_ms;
+            heap = (soft_timer_entry_t*)mp_pairheap_push(soft_timer_lt, &heap->pairheap, &entry->pairheap);
         }
     }
-    MP_STATE_PORT(soft_timer_head) = head;
-    if (head == NULL) {
+    MP_STATE_PORT(soft_timer_heap) = heap;
+    if (heap == NULL) {
         // No more timers left, set largest delay possible
         soft_timer_next = uwTick;
     } else {
         // Set soft_timer_next so SysTick calls us back at the correct time
-        soft_timer_schedule_systick(head->expiry_ms);
+        soft_timer_schedule_systick(heap->expiry_ms);
     }
 }
 
 void soft_timer_insert(soft_timer_entry_t *entry) {
     uint32_t irq_state = raise_irq_pri(IRQ_PRI_PENDSV);
-    soft_timer_entry_t **head_ptr = &MP_STATE_PORT(soft_timer_head);
-    while (*head_ptr != NULL && TICKS_DIFF(entry->expiry_ms, (*head_ptr)->expiry_ms) >= 0) {
-        head_ptr = &(*head_ptr)->next;
-    }
-    entry->next = *head_ptr;
-    *head_ptr = entry;
-    if (head_ptr == &MP_STATE_PORT(soft_timer_head)) {
+    MP_STATE_PORT(soft_timer_heap) = (soft_timer_entry_t*)mp_pairheap_push(soft_timer_lt, &MP_STATE_PORT(soft_timer_heap)->pairheap, &entry->pairheap);
+    if (entry == MP_STATE_PORT(soft_timer_heap)) {
         // This new timer became the earliest one so set soft_timer_next
-        soft_timer_schedule_systick((*head_ptr)->expiry_ms);
+        soft_timer_schedule_systick(entry->expiry_ms);
     }
     restore_irq_pri(irq_state);
 }
 
 void soft_timer_remove(soft_timer_entry_t *entry) {
     uint32_t irq_state = raise_irq_pri(IRQ_PRI_PENDSV);
-    soft_timer_entry_t **cur = &MP_STATE_PORT(soft_timer_head);
-    while (*cur != NULL) {
-        if (*cur == entry) {
-            *cur = entry->next;
-            break;
-        }
-    }
+    MP_STATE_PORT(soft_timer_heap) = (soft_timer_entry_t*)mp_pairheap_delete(soft_timer_lt, &MP_STATE_PORT(soft_timer_heap)->pairheap, &entry->pairheap);
     restore_irq_pri(irq_state);
 }

ports/stm32/softtimer.h

@@ -26,14 +26,13 @@
 #ifndef MICROPY_INCLUDED_STM32_SOFTTIMER_H
 #define MICROPY_INCLUDED_STM32_SOFTTIMER_H
 
-#include "py/obj.h"
+#include "py/pairheap.h"
 
 #define SOFT_TIMER_MODE_ONE_SHOT (1)
 #define SOFT_TIMER_MODE_PERIODIC (2)
 
 typedef struct _soft_timer_entry_t {
-    mp_obj_base_t base; // so struct can be used as an object and still be traced by GC
-    struct _soft_timer_entry_t *next;
+    mp_pairheap_t pairheap;
     uint32_t mode;
     uint32_t expiry_ms;
     uint32_t delta_ms; // for periodic mode