pubsub.c

#include <stdlib.h>
#include <stdio.h>

typedef char EventName[255];
typedef union HandlerData {
   int i;
   float f;
   char str[255];
} HandlerData;
typedef void (*EventHandler)(EventName event, HandlerData *data);
typedef struct EventItem {
  EventName *name;
  EventHandler handler;
  HandlerData *data;
} EventItem;
typedef struct EventBus {
  EventItem *events;
  unsigned int maxEvents;
  unsigned int cursorEvents;
} EventBus;

void handler(EventName event, HandlerData *data) {
  printf("yes $%s %f\n", event, data->f);
}

void handler2(EventName event, HandlerData *data) {
  printf("no $%s %d\n", event, data->i);
}

EventBus EventBus_init() {
  EventItem *events = malloc(1 * sizeof(EventItem));
  EventBus bus = { events, 0, 0 };

  return bus;
}

void EventBus_addEvent(EventBus *bus, EventName *name, EventHandler handler, HandlerData *data) {
  if (bus->cursorEvents == bus->maxEvents) {
    EventItem *events = bus->events;
    bus->events = realloc(events, sizeof(EventItem) * (bus->maxEvents++ + 1));
  }

  bus->events[bus->cursorEvents++] = (EventItem) {
    .name = name, 
    .handler = handler,
    .data = data
  };
}

void moveEvents(EventItem *events, unsigned int start, unsigned int max) {
  if ( start < max)
    for (unsigned int i = start; i < max; i++) {
      events[i] = events[i + 1];
    }
}

void EventBus_removeEvent(EventBus *bus, EventName *name, EventHandler handler) {
  EventItem *events = bus->events;
  unsigned int counter = 0;

  for (unsigned int i = 0; i < bus->maxEvents; i++) {
    EventItem event = events[i];

    if (event.name == name && event.handler == handler) {
      counter += 1;
      moveEvents(events, i, bus->maxEvents - 1);
    }
  }

  if (counter > 0) {
    bus->maxEvents = bus->maxEvents - counter;
    bus->cursorEvents = bus->maxEvents;
    bus->events = realloc(events, sizeof(EventItem) * (bus->maxEvents));
  }
}

void EventBus_triggerEvent(EventBus *bus, EventName *name) {
  for (unsigned int i = 0; i < bus->maxEvents; i++) {
    EventItem event = bus->events[i];
    if (event.name == name) {
      event.handler(*event.name, event.data);
    }
  }
}

int main() {
  EventBus bus = EventBus_init();
  EventName name = "test/1";
  EventName name2 = "test/2";

  HandlerData data = { .f =  2.0 };
  HandlerData data2 = { .i =  0 };

  EventBus_addEvent(&bus, &name, &handler, &data);
  EventBus_addEvent(&bus, &name2, &handler2, &data2);
  EventBus_triggerEvent(&bus, &name);
  EventBus_removeEvent(&bus, &name, &handler);
  EventBus_triggerEvent(&bus, &name);

  data2.i = 2;
  EventBus_triggerEvent(&bus, &name2);

  return 0;
}