save_blocker.cpp

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/*
    Copyright (C) 2009 - 2021
    by Daniel Franke
    Part of the Battle for Wesnoth Project https://www.wesnoth.org/

    This program is free software; you can redistribute it and/or modify
    it under the terms of the GNU General Public License as published by
    the Free Software Foundation; either version 2 of the License, or
    (at your option) any later version.
    This program is distributed in the hope that it will be useful,
    but WITHOUT ANY WARRANTY.

    See the COPYING file for more details.
*/

#include "save_blocker.hpp"
#include <exception>
#include <iostream>

play_controller* save_blocker::controller_ = nullptr;
void (play_controller::*save_blocker::callback_)() = nullptr;
SDL_sem* save_blocker::sem_ = SDL_CreateSemaphore(1);

save_blocker::save_blocker() {
    block();
}

save_blocker::~save_blocker() {
    try {
    unblock();
    if(controller_ && callback_) {
        (controller_->*callback_)();
        controller_ = nullptr;
        callback_ = nullptr;
    }
    } catch (const std::exception & e) {
        std::cerr << "Save blocker dtor swallowing an exception: " << e.what() << "\n";
    }
}

void save_blocker::on_unblock(play_controller* controller, void (play_controller::*callback)()) {
    if(try_block()) {
        unblock();
        (controller->*callback)();
    } else {
        controller_ = controller;
        callback_ = callback;
    }
}

bool save_blocker::saves_are_blocked() {
    return SDL_SemValue(sem_) == 0;
}

void save_blocker::block() {
    SDL_SemWait(sem_);
}

bool save_blocker::try_block() {
    return SDL_SemTryWait(sem_) == 0;
}

void save_blocker::unblock() {
    assert(SDL_SemValue(sem_) == 0);
    SDL_SemPost(sem_);
}