4.1.5.1 Event handlers

Events are handled by EventHandlers which can rely either on portals or, when delivered inside the kernel, on function calls. The default handler simply does nothing.

<Off event handler. >= (U->)
// An event handler. 
class off_EventHandler {
public:
  // Calls the handler
  virtual err_t operator()(const off_EventReq *ev, vm_size_t s) {
    (void)ev; (void)s;
    return EOK;
  }
};

class off_KrnEventHandler : public off_EventHandler {
public:
  <Other public methods of off_KrnEventHandler. >

  // Calls the handler
  virtual err_t operator()(const off_EventReq *ev, vm_size_t s);
private:
  <Other private members of off_KrnEventHandler. >
};

class off_UsrEventHandler : public off_EventHandler {
public:
  <Other public methods of off_UsrEventHandler. >

  // Calls the handler
  virtual err_t operator()(const off_EventReq *ev, vm_size_t s);
private:
  <Other private members of off_UsrEventHandler. >
};

Defines off_EventHandler, off_KrnEventHandler, off_UsrEventHandler (links are to index).

There is a null handler defined to do nothing.

<Off null event handler. >= (U->)
const off_EventHandler OFF_NULL_HANDLER;

But usually, event handlers will be created either to dispatch to a local function or to a system portal.

<Other public methods of off_KrnEventHandler. >= (<-U)
// Creates an in-kernel event handler.
off_KrnEventHandler(off_PrtlHandlerFn *h);

<Other public methods of off_UsrEventHandler. >= (<-U)
// Creates an in-kernel event handler.
off_UsrEventHandler(const off_prtl_id_t &p);

Where PrtlHandlerFn is a local function servicing the portal invocation. The event handler constructor simply records the handler.

<off_KrnEventHandler::off_KrnEventHandler implementation. >= (U->)
// Creates an in-kernel event handler.
off_KrnEventHandler::off_KrnEventHandler(off_PrtlHandlerFn *h) :
  k_hndlr(h)
{;}

<Other private members of off_KrnEventHandler. >= (<-U)
off_PrtlHandlerFn *k_hndlr;     // The handling function.

<off_UsrEventHandler::off_UsrEventHandler implementation. >= (U->)
// Creates a cross-domain event handler.
off_UsrEventHandler::off_UsrEventHandler(const off_prtl_id_t &p) :
  u_hndlr(p)
{;}

<Other private members of off_UsrEventHandler. >= (<-U)
off_prtl_id_t u_hndlr;     // The handling portal.

<off_KrnEventHandler::operator() implementation. >= (U->)
err_t off_KrnEventHandler::operator()(const off_EventReq *ev, vm_size_t s)
{
  return (*k_hndlr)(s,(void*)ev);
}

<off_UsrEventHandler::operator() implementation. >= (U->)
err_t off_UsrEventHandler::operator()(const off_EventReq *ev, vm_size_t s)
{
  (void)ev;
  return ENOSYS;
}