use single constexpr definition instead of repeated expression.

cores/esp8266/Schedule.cpp

@@ -50,6 +50,8 @@ static recurrent_fn_t* rLast = nullptr;
 // The target time for scheduling the next timed recurrent function 
 static decltype(micros()) rTarget;
 
+constexpr decltype(micros()) HALF_MAX_MICROS = ~static_cast<decltype(micros())>(0) >> 1;
+
 // Returns a pointer to an unused sched_fn_t,
 // or if none are available allocates a new one,
 // or nullptr if limit is reached
@@ -106,7 +108,7 @@ bool schedule_function(const std::function<void(void)>& fn)
 
 IRAM_ATTR // (not only) called from ISR
 bool schedule_recurrent_function_us(const std::function<bool(void)>& fn,
-    uint32_t repeat_us, const std::function<bool(void)>& alarm)
+    decltype(micros()) repeat_us, const std::function<bool(void)>& alarm)
 {
     assert(repeat_us < decltype(recurrent_fn_t::callNow)::neverExpires); //~26800000us (26.8s)
 
@@ -126,7 +128,7 @@ bool schedule_recurrent_function_us(const std::function<bool(void)>& fn,
     const auto now = micros();
     const auto itemRemaining = item->callNow.remaining();
     const int32_t remaining = rTarget - now;
-    if (!rFirst || (remaining > 0 && static_cast<uint32_t>(remaining) > itemRemaining))
+    if (!rFirst || (remaining > 0 && static_cast<decltype(micros()>(remaining) > itemRemaining))
     {
         rTarget = now + itemRemaining;
     }
@@ -144,17 +146,17 @@ bool schedule_recurrent_function_us(const std::function<bool(void)>& fn,
     return true;
 }
 
-uint32_t get_scheduled_recurrent_delay_us()
+decltype(micros()) get_scheduled_recurrent_delay_us()
 {
-    if (!rFirst) return ~static_cast<decltype(micros())>(0) >> 1;
+    if (!rFirst) return HALF_MAX_MICROS;
     // handle already expired rTarget.
     const int32_t remaining = rTarget - micros();
-    return (remaining > 0) ? static_cast<uint32_t>(remaining) : 0;
+    return (remaining > 0) ? static_cast<decltype(micros())>(remaining) : 0;
 }
 
-uint32_t get_scheduled_delay_us()
+decltype(micros()) get_scheduled_delay_us()
 {
-    return sFirst ? 0 : ~static_cast<decltype(micros())>(0) >> 1;
+    return sFirst ? 0 : HALF_MAX_MICROS;
 }
 
 void run_scheduled_functions()
@@ -223,7 +225,7 @@ void run_scheduled_recurrent_functions()
 
     // prevent scheduling of new functions during this run
     stop = rLast;
-    rTarget = micros() + (~static_cast<decltype(micros())>(0) >> 1);
+    rTarget = micros() + HALF_MAX_MICROS;
 
     do
     {
@@ -262,7 +264,7 @@ void run_scheduled_recurrent_functions()
             const auto now = micros();
             const auto currentRemaining = current->callNow.remaining();
             const int32_t remaining = rTarget - now;
-            if (remaining > 0 && static_cast<uint32_t>(remaining) > currentRemaining)
+            if (remaining > 0 && static_cast<decltype(micros)>(remaining) > currentRemaining)
             {
                 rTarget = now + currentRemaining;
             }

cores/esp8266/Schedule.h

@@ -42,7 +42,7 @@
 // get_scheduled_recurrent_delay_us() is used by delay() to give a chance to
 // all recurrent functions to run per their timing requirement.
 
-uint32_t get_scheduled_recurrent_delay_us();
+decltype(micros()) get_scheduled_recurrent_delay_us();
 
 // scheduled functions called once:
 //
@@ -65,7 +65,7 @@ uint32_t get_scheduled_recurrent_delay_us();
 // values, viz. 0 in case of any pending scheduled functions, or a large delay time if
 // there is no function in the queue.
 
-uint32_t get_scheduled_delay_us();
+decltype(micros()) get_scheduled_delay_us();
 
 bool schedule_function (const std::function<void(void)>& fn);
 
@@ -93,7 +93,7 @@ void run_scheduled_functions();
 //   any remaining delay from repeat_us is disregarded, and fn is executed.
 
 bool schedule_recurrent_function_us(const std::function<bool(void)>& fn,
-    uint32_t repeat_us, const std::function<bool(void)>& alarm = nullptr);
+    decltype(micros()) repeat_us, const std::function<bool(void)>& alarm = nullptr);
 
 // Test recurrence and run recurrent scheduled functions.
 // (internally called at every `yield()` and `loop()`)