ws: directly iterate over internal callbacks array (#2248)

tnx to @RDobrinov
https://gist.github.com/RDobrinov/9e739fd77990d0a77fc1b867176bf48c

code/espurna/ws_internal.h

@@ -31,32 +31,6 @@ struct ws_ticket_t {
 // WS callbacks
 // -----------------------------------------------------------------------------
 
-struct ws_counter_t {
-
- ws_counter_t() : current(0), start(0), stop(0) {}
-
- ws_counter_t(uint32_t start, uint32_t stop) :
- current(start), start(start), stop(stop) {}
-
- void reset() {
- current = start;
- }
-
- void next() {
- if (current < stop) {
- ++current;
- }
- }
-
- bool done() {
- return (current >= stop);
- }
-
- uint32_t current;
- uint32_t start;
- uint32_t stop;
-};
-
 struct ws_data_t {
 
  enum mode_t {
@@ -69,46 +43,47 @@ struct ws_data_t {
  client_id(0),
  mode(ALL),
  callbacks(*storage.get()),
- counter(0, 1)
+ current(callbacks.begin())
  {}
 
  ws_data_t(uint32_t client_id, const ws_on_send_callback_f& cb) :
  storage(new ws_on_send_callback_list_t {cb}),
  client_id(client_id),
  mode(ALL),
  callbacks(*storage.get()),
- counter(0, 1)
+ current(callbacks.begin())
  {}
 
  ws_data_t(const uint32_t client_id, ws_on_send_callback_list_t&& callbacks, mode_t mode = SEQUENCE) :
  storage(new ws_on_send_callback_list_t(std::move(callbacks))),
  client_id(client_id),
  mode(mode),
  callbacks(*storage.get()),
- counter(0, (storage.get())->size())
+ current(callbacks.begin())
  {}
 
  ws_data_t(const uint32_t client_id, const ws_on_send_callback_list_t& callbacks, mode_t mode = SEQUENCE) :
  client_id(client_id),
  mode(mode),
  callbacks(callbacks),
- counter(0, callbacks.size())
+ current(callbacks.begin())
  {}
 
  bool done() {
- return counter.done();
+ return current == callbacks.end();
  }
 
  void sendAll(JsonObject& root) {
- while (!counter.done()) counter.next();
+ current = callbacks.end();
  for (auto& callback : callbacks) {
  callback(root);
  }
  }
 
  void sendCurrent(JsonObject& root) {
- callbacks[counter.current](root);
- counter.next();
+ if (current == callbacks.end()) return;
+ (*current)(root);
+ ++current;
  }
 
  void send(JsonObject& root) {
@@ -123,7 +98,7 @@ struct ws_data_t {
  const uint32_t client_id;
  const mode_t mode;
  const ws_on_send_callback_list_t& callbacks;
- ws_counter_t counter;
+ ws_on_send_callback_list_t::const_iterator current;
 };
 
 // -----------------------------------------------------------------------------