Question

Imagine a device full of sensors. Now, in case a sensor x detects something, something should happen. Meanwhile, in case something else is detected, like two sensors detects two different things, then, this device must behave differently.

From webdesign (so javascript) I learned about Events, for example (using jquery) $(".x").on("click", function(){}) or from angularjs $scope.watch("name_of_var", function()).

Is there any possibility to replicate this behaviour in C, without using complex libraries?

Answer 1

I would assume you’re owning an embedded system with access to interrupts or a major event loop in a separate thread, otherwise this isn’t possible..

A basic model for event handling is here:

#define NOEVENT 0

typedef void *(*EventHandler)(void *);

void *doNothing(void *p){/*do nothing absolutely*/ return NULL; }
typedef struct _event{
  EventHandler handler;
}Event, *PEvent;

Event AllEvents[1000];
unsigned short counter = 0;
void InitEvents()
{
    LOCK(AllEvents);
    for(int i = 0; i < 1000; i++){ 
        AllEvents[i].handler = doNothing;
    }
    UNLOCK(AllEvents);
}
void AddEvent(int EventType, EventHandler ev_handler)
{
    LOCK(AllEvents);
    AllEvents[EventType].handler = ev_handler;
    UNLOCK(AllEvents);
}

void RemoveEvent(int EventType, EventHandler ev_handler)
{
   LOCK(AllEvents);
   AllEvents[EventType] = doNothing;
   UNLOCK(AllEvents); /*to safeguard the event loop*/
}

/*to be run in separate thread*/
void EventLoop()
{
   int event = NOEVENT;
   EventHandler handler;
   while(1){
       while(event == NOEVENT)event=GetEvents();
       handler = AllEvents[event].handler;
       handler();/*perform on an event*/
  }
}