pass lambdas with const refs

Author: d-a-v

cores/esp8266/Schedule.cpp

@@ -51,7 +51,7 @@ static void recycle_fn_unsafe(scheduled_fn_t* fn)
 }
 
 IRAM_ATTR // called from ISR
-bool schedule_function_us(mFuncT fn, uint32_t repeat_us)
+bool schedule_function_us(const mFuncT& fn, uint32_t repeat_us)
 {
     assert(repeat_us < decltype(scheduled_fn_t::callNow)::neverExpires); //~26800000us (26.8s)
 
@@ -75,9 +75,9 @@ bool schedule_function_us(mFuncT fn, uint32_t repeat_us)
 }
 
 IRAM_ATTR // called from ISR
-bool schedule_function(std::function<void(void)> fn)
+bool schedule_function(const std::function<void(void)>& fn)
 {
-    return schedule_function_us([&fn](){ fn(); return false; }, 0);
+    return schedule_function_us([fn](){ fn(); return false; }, 0);
 }
 
 void run_scheduled_functions()

cores/esp8266/Schedule.h

@@ -17,12 +17,12 @@
 // Note: there is no mechanism for cancelling scheduled functions.
 // Keep that in mind when binding functions to objects which may have short lifetime.
 // Returns false if the number of scheduled functions exceeds SCHEDULED_FN_MAX_COUNT.
-bool schedule_function(std::function<void(void)> fn);
+bool schedule_function(const std::function<void(void)>& fn);
 
 // Run given function periodically about every <repeat_us> microseconds until it returns false.
 // Note that it may be more than <repeat_us> microseconds between calls if `yield` is not called
 // frequently, and therefore should not be used for timing critical operations.
-bool schedule_function_us(std::function<bool(void)> fn, uint32_t repeat_us);
+bool schedule_function_us(const std::function<bool(void)>& fn, uint32_t repeat_us);
 
 // Run all scheduled functions.
 // Use this function if your are not using `loop`, or `loop` does not return