Added option -s,--seed=NUMBER to set a specific random seed.

alfmep · Dec 9, 2021 · 8727d83 · 8727d83
1 parent d5a60a4
commit 8727d83
Show file tree

Hide file tree

Showing 5 changed files with 33 additions and 6 deletions.
diff --git a/README b/README
@@ -12,6 +12,7 @@ Usage: macgen [OPTIONS]
   -u, --uppercase    Print hex characters in uppercase instead of lowercase.
   -n, --no-newline   Do not output the trailing newline.
   -r, --repeat=NUM   Generate NUM MAC addresses.
+  -s, --seed=NUMBER  Set a specific random seed.
   -v, --version      Print version and exit.
   -h, --help         Print this help message.
 

diff --git a/configure.ac b/configure.ac
@@ -1,4 +1,4 @@
-AC_INIT([macgen], [1.0.1], [info@ultramarin.se])
+AC_INIT([macgen], [1.0.2], [info@ultramarin.se])
 AM_INIT_AUTOMAKE([-Wall -Werror foreign dist-bzip2])
 
 AC_PROG_CC

diff --git a/src/appargs.cpp b/src/appargs.cpp
@@ -17,6 +17,8 @@
  * along with this program.  If not, see <http://www.gnu.org/licenses/>.
  */
 #include <iostream>
+#include <chrono>
+#include <string>
 #include <getopt.h>
 #include <appargs.hpp>
 
@@ -46,6 +48,7 @@ namespace macgen {
             << "  -u, --uppercase    Print hex characters in uppercase instead of lowercase." << std::endl
             << "  -n, --no-newline   Do not output the trailing newline." << std::endl
             << "  -r, --repeat=NUM   Generate NUM MAC addresses." << std::endl
+            << "  -s, --seed=NUMBER  Set a specific random seed." << std::endl
             << "  -v, --version      Print version and exit." << std::endl
             << "  -h, --help         Print this help message." << std::endl
             << std::endl;
@@ -70,11 +73,16 @@ namespace macgen {
             { "uppercase",  no_argument,       0, 'u'},
             { "no-newline", no_argument,       0, 'n'},
             { "repeat",     required_argument, 0, 'r'},
+            { "seed",       required_argument, 0, 's'},
             { "version",    no_argument,       0, 'v'},
             { "help",       no_argument,       0, 'h'},
             { 0, 0, 0, 0}
         };
-        const char* arg_format = "mcdunr:vh";
+        const char* arg_format = "mcdunr:s:vh";
+
+        // Set default random seed, milliseconds since epoch
+        auto now = std::chrono::system_clock().now ();
+        seed = std::chrono::duration_cast<std::chrono::milliseconds>(now.time_since_epoch()).count ();
 
         while (1) {
             int c = getopt_long (argc, argv, arg_format, long_options, NULL);
@@ -97,10 +105,24 @@ namespace macgen {
                 no_newline = true;
                 break;
             case 'r':
-                repeat = atoi (optarg);
-                if (repeat == 0) {
-                    std::cerr << "Invalid repeat value: " << optarg << std::endl << std::endl;
-                    print_usage_and_exit (std::cerr, 1);
+                try {
+                    repeat = std::stoi (optarg);
+                }catch (...) {
+                    repeat = -1;
+                }
+                if (repeat < 1) {
+                    std::cerr << "Error: Invalid repeat value: " << optarg
+                              << " (use option '-h' for help)" << std::endl;
+                    exit (1);
+                }
+                break;
+            case 's':
+                try {
+                    seed = (unsigned long) std::stol (optarg, nullptr, 0);
+                }catch(...) {
+                    std::cerr << "Error: Invalid seed value: " << optarg
+                              << " (use option '-h' for help)" << std::endl;
+                    exit (1);
                 }
                 break;
             case 'v':

diff --git a/src/appargs.hpp b/src/appargs.hpp
@@ -28,6 +28,7 @@ namespace macgen {
         bool uppercase;
         bool no_newline;
         int repeat;
+        unsigned long seed;
 
         appargs (int argc, char* argv[]);
     };

diff --git a/src/main.cpp b/src/main.cpp
@@ -34,6 +34,9 @@ int main (int argc, char* argv[])
     std::default_random_engine re (rd());
     std::uniform_int_distribution<uint16_t> random_value (1, 65535);
 
+    // Set random seed
+    re.seed (args.seed);
+
     std::cout << std::hex;
     if (args.uppercase)
         std::cout << std::uppercase;