Event Callback


In this example drizzle_event_watch_fn() is used to set a custom I/O event watcher function for a drizzle structure. It is used to integrate libdrizzle-redux with a custom event loop. The callback will be invoked to register or deregister interest in events for a connection. When the events are triggered, drizzle_set_revents() should be called to indicate which events are ready. The event loop should stop waiting for these events, as libdrizzle-redux will call the callback again if it is still interested. To resume processing, the libdrizzle-redux function that returned DRIZZLE_RETURN_IO_WAIT should be called again.

The custom callback must have a signature as shown:

drizzle_return_t (drizzle_event_watch_fn)(drizzle_con_st *con, short events, void *context);


#include <libdrizzle-5.1/libdrizzle.h>
#include <libdrizzle-5.1/constants.h>

extern drizzle_return_t drizzle_event_callback(drizzle_st *con, short events,
void *context);

extern drizzle_return_t drizzle_event_callback(drizzle_st *con, short events,
  void *context)
  // The context defined for the drizzle connection
  int* drizzle_cxt = (int*) drizzle_context(con);

  // The context defined for the callback function
  int* callback_cxt = (int*) context;

  printf("Called drizzle_event_callback\n");


int main(int argc, char *argv[])
  (void) argc;
  (void) argv;

  int cxt_a = 1;
  int cxt_b = 0;

  drizzle_st *con = drizzle_create("localhost", 3306, "root", "", "libdrizzle", 0);
  if (con == NULL)
    printf("Drizzle connection object creation error\n");
    return EXIT_FAILURE;

  // Set drizzle dummy context
  drizzle_set_context(con, (void*)&cxt_a);

  // Set user defined callback function event_watch_fn
  drizzle_set_event_watch_fn(con, drizzle_event_callback, (void*)&cxt_b);

  drizzle_return_t driz_ret= drizzle_connect(con);

  if (ret != DRIZZLE_RETURN_OK)
    printf("Drizzle connection failure\n");
    return EXIT_FAILURE;

  driz_ret= drizzle_quit(con);

  return EXIT_SUCCESS;