message_bus.cpp

/* This file is part of the "ST" project.
 * You may use, distribute or modify this code under the terms
 * of the GNU General Public License version 2.
 * See LICENCE.txt in the root directory of the project.
 *
 * Author: Maxim Atanasov
 * E-mail: maxim.atanasov@protonmail.com
 */
 
#include <message_bus.hpp>
#include <ST_util/pool_allocator_256.hpp>
 
//message_bus implementation=====================================================
 
void message_bus::send_msg(message *arg) {
    std::vector<subscriber *> *temp = &subscribers[arg->msg_name];
    uint64_t size = temp->size();
    //Locks aren't really needed here as there won't be any new subscribers in the middle of the game
    //(if you do want to have subsystems subscribe at random times you should definitely add locks)
 
    //TODO: Branch needed? In practice, no messages without subscribers to them will be sent
    //The branch cannot be removed with an #ifdef though, as the msg_bus is a library.
    if (size != 0) [[likely]] {
        temp->operator[](0)->push_message(arg);
        for (uint64_t i = 1; i < size; ++i) {
            temp->operator[](i)->push_message(arg->make_copy()); //yes all queues are thread-safe so this is fine
        }
    }
}
 
static bool singleton_initialized = false;
 
message_bus::message_bus() {
    if (singleton_initialized) {
        throw std::runtime_error("The message bus cannot be initialized more than once!");
    } else {
        singleton_initialized = true;
    }
}
 
message_bus::~message_bus() {
    subscribers.clear();
    singleton_initialized = false;
}
 
void message_bus::clear() {
    subscribers.clear();
}
 
void message_bus::subscribe(uint8_t msg, subscriber *sub) {
    subscribers[msg].emplace_back(sub);
}