Answers for "c++ mutex"

std::mutex

#include <iostream>
#include <map>
#include <string>
#include <chrono>
#include <thread>
#include <mutex>
 
std::map<std::string, std::string> g_pages;
std::mutex g_pages_mutex;
 
void save_page(const std::string &url)
{
    // simulate a long page fetch
    std::this_thread::sleep_for(std::chrono::seconds(2));
    std::string result = "fake content";
 
    std::lock_guard<std::mutex> guard(g_pages_mutex);
    g_pages[url] = result;
}
 
int main() 
{
    std::thread t1(save_page, "http://foo");
    std::thread t2(save_page, "http://bar");
    t1.join();
    t2.join();
 
    // safe to access g_pages without lock now, as the threads are joined
    for (const auto &pair : g_pages) {
        std::cout << pair.first << " => " << pair.second << 'n';
    }
}

cpp mutex

#include <mutex>
#include <vector>
std::mutex door;    // mutex declaration
std::vector<int> v; // shared data
door.lock();
/*-----------------------*/
/* This is a thread-safe zone: just one thread at the time allowed
 * 
 * Unique ownership of vector v guaranteed 
 */
/*-----------------------*/
door.unlock();