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74 lines (50 loc) · 1.55 KB
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/*
THE DATA SERVER PROBLEM
Version B: Solving the problem using a semaphore
*/
#include <iostream>
#include <string>
#include <vector>
#include <chrono>
#include <thread>
#include <semaphore>
using namespace std;
#define sleepsec(secs) \
do { std::this_thread::sleep_for(std::chrono::seconds(secs)); } while (0)
using cntsemaphore = std::counting_semaphore<>;
void checkAuthUser() {
cout << "[ Auth ] Start" << endl;
// Send request to authenticator, check permissions, encrypt, decrypt...
sleepsec(20);
cout << "[ Auth ] Done" << endl;
}
void processFiles(const vector<string>& lstFileName, cntsemaphore& sem) {
for (auto&& fileName : lstFileName) {
// Read file
cout << "[ ReadFile ] Start " << fileName << endl;
sleepsec(10);
cout << "[ ReadFile ] Done " << fileName << endl;
sem.release();
// Write log into disk
sleepsec(5);
cout << "[ WriteLog ]" << endl;
}
}
void processRequest() {
const vector<string> lstFileName = { "foo.html", "bar.json" };
cntsemaphore sem(0);
// The server checks auth user while reading files, concurrently
std::thread th(&processFiles, std::cref(lstFileName), std::ref(sem));
checkAuthUser();
// The server waits for completion of loading files
for (size_t i = lstFileName.size(); i > 0; --i) {
sem.acquire();
}
cout << "\nNow user is authorized and files are loaded" << endl;
cout << "Do other tasks...\n" << endl;
th.join();
}
int main() {
processRequest();
return 0;
}