update, see readme for usage

ntpdetails.cpp

@@ -3,48 +3,73 @@
 #include <chrono>
 #include <cstring>
 #include <asio.hpp>
+#include <regex>
+#include <limits>
 
 const int NTP_PORT = 123;
 const int NTP_PACKET_SIZE = 48;
 
-void queryNTPServer(const std::string& server) {
+void queryNTPServer(const std::string& server, int utc_offset) {
     try {
         asio::io_context io_context;
 
+        // Resolve the server using IPv4
         asio::ip::udp::resolver resolver(io_context);
         asio::ip::udp::resolver::query query(asio::ip::udp::v4(), server, std::to_string(NTP_PORT));
         asio::ip::udp::endpoint endpoint = *resolver.resolve(query).begin();
 
+        // Create a socket
         asio::ip::udp::socket socket(io_context);
         socket.open(asio::ip::udp::v4());
 
+        // Create NTP request packet
         std::array<unsigned char, NTP_PACKET_SIZE> request{};
-        request[0] = 0b11100011; 
+        request[0] = 0b11100011; // LI, Version, Mode: (3-3-3 for client mode)
 
+        // Record start time for ping calculation
         auto start_time = std::chrono::high_resolution_clock::now();
 
+        // Send the request
         socket.send_to(asio::buffer(request), endpoint);
 
+        // Receive response
         std::array<unsigned char, NTP_PACKET_SIZE> response{};
         asio::ip::udp::endpoint sender_endpoint;
         socket.receive_from(asio::buffer(response), sender_endpoint);
 
+        // Record end time for ping calculation
         auto end_time = std::chrono::high_resolution_clock::now();
         std::chrono::duration<double> ping = end_time - start_time;
 
+        // Extract the timestamp
         const unsigned long long NTP_TIMESTAMP_DELTA = 2208988800ULL;
         unsigned long long seconds = (static_cast<unsigned long long>(response[40]) << 24) |
-                                     (static_cast<unsigned long long>(response[41]) << 16) |
+        (static_cast<unsigned long long>(response[41]) << 16) |
-                                     (static_cast<unsigned long long>(response[42]) << 8) |
+        (static_cast<unsigned long long>(response[42]) << 8) |
-                                     static_cast<unsigned long long>(response[43]);
+        (static_cast<unsigned long long>(response[43]));
         seconds -= NTP_TIMESTAMP_DELTA;
 
-        std::time_t time = static_cast<std::time_t>(seconds);
+        // Convert timestamp to human-readable format
-        std::tm* utc_time = std::gmtime(&time);
+        std::time_t raw_time = static_cast<std::time_t>(seconds);
+        std::tm* utc_time = std::gmtime(&raw_time);
 
+        // Calculate adjusted time for the UTC offset
+        std::time_t adjusted_time = raw_time + (utc_offset * 3600);
+        std::tm* local_time = std::gmtime(&adjusted_time);
+
+        // Print details
         std::cout << "Details of " << server << "\n";
-        std::cout << "Time: " << std::put_time(utc_time, "%H:%M:%S") << " UTC\n";
+
-        std::cout << "Date: " << std::put_time(utc_time, "%Y-%m-%d") << "\n";
+        if (utc_offset == 0) {
+            // Print UTC time if no timezone is provided
+            std::cout << "Time: " << std::put_time(utc_time, "%H:%M:%S") << " UTC\n";
+        } else {
+            // Print adjusted time for the provided UTC offset
+            std::cout << "Time (utc" << (utc_offset >= 0 ? "+" : "") << utc_offset << "): "
+            << std::put_time(local_time, "%H:%M:%S") << "\n";
+        }
+
+        std::cout << "Date: " << std::put_time(local_time, "%Y-%m-%d") << "\n";
         std::cout << "Ping: " << std::fixed << std::setprecision(3) << ping.count() * 1000 << " ms\n";
 
     } catch (const std::exception& e) {
@@ -52,13 +77,50 @@ void queryNTPServer(const std::string& server) {
     }
 }
 
+int parseUTCOffset(const std::string& timezone) {
+    std::regex tz_regex(R"(^utc([+-]?\d+)$)", std::regex::icase);
+    std::smatch match;
+    if (std::regex_match(timezone, match, tz_regex)) {
+        try {
+            int offset = std::stoi(match[1]);
+            if (offset < -12 || offset > 14) { // Limit UTC offsets to reasonable values
+                throw std::out_of_range("UTC offset out of range (-12 to +14)");
+            }
+            return offset;
+        } catch (const std::exception&) {
+            throw std::invalid_argument("Invalid UTC offset");
+        }
+    }
+    throw std::invalid_argument("Invalid timezone format");
+}
+
 int main(int argc, char* argv[]) {
-    if (argc != 2) {
+    if (argc < 2 || argc > 3) {
-        std::cerr << "Usage: " << argv[0] << " <NTP server>\n";
+        std::cerr << "Usage: " << argv[0] << " [-t=utcX] <NTP server>\n";
         return 1;
     }
 
-    std::string server = argv[1];
+    std::string timezone_flag = "-t=utc0";
-    queryNTPServer(server);
+    std::string server;
+
+    if (argc == 3) {
+        timezone_flag = argv[1];
+        server = argv[2];
+    } else {
+        server = argv[1];
+    }
+
+    int utc_offset = 0;
+    if (timezone_flag.rfind("-t=", 0) == 0 || timezone_flag.rfind("--timezone=", 0) == 0) {
+        std::string timezone = timezone_flag.substr(timezone_flag.find('=') + 1);
+        try {
+            utc_offset = parseUTCOffset(timezone);
+        } catch (const std::exception& e) {
+            std::cerr << "Error: " << e.what() << "\n";
+            return 1;
+        }
+    }
+
+    queryNTPServer(server, utc_offset);
     return 0;
-}
+}