C++ify genkey

Switches to iostream for user I/O, implements -h/--help, adds default random pubkey generation feature and handles wrong usage gracefully.

Author: TheAssassin

src/engine/genkey.cpp

@@ -1,30 +1,56 @@
+#include <algorithm>
 #include <sys/time.h>
-#include <sys/types.h>
-#include <unistd.h>
-#include <errno.h>
-#include <signal.h>
+#include <random>
+#include <iostream>
 
 #include "cube.h"
 
 int main(int argc, char **argv)
 {
-    //Generate key pair: genkey <seed>
-    if(argc == 2)
-    {
+    std::string argv1;
+
+    // generate key pair with random seed generated by OS
+    if (argc == 1) {
+        std::random_device rd;
+        std::mt19937 mt(rd());
+        std::uniform_int_distribution<> distribution(1, 255);
+        std::generate_n(std::back_inserter(argv1), 255, [&]() { return distribution(mt); });
+        argc = 2;
+    } else {
+        argv1 = argv[1];
+    }
+
+    // support --help/-h
+    if (argv1 == "--help" || argv1 == "-h") {
+        std::cerr << "Blue Nebula genkey utility" << std::endl;
+        std::cerr << std::endl;
+        std::cerr << "Usage:" << std::endl;
+        std::cerr << std::endl;
+        std::cerr << "  genkey                     generate private and public key using random seed" << std::endl;
+        std::cerr << "  genkey <seed>              generate private and public key using provided seed" << std::endl;
+        std::cerr << "  genkey <pubkey> <privkey>  check if public key belongs to private key" << std::endl;
+        std::cerr << "  genkey -h/--help           print this help" << std::endl;
+        return EXIT_SUCCESS;
+    }
+
+    // generate key pair with provided seed
+    if(argc == 2) {
         vector<char> privkey, pubkey;
-        genprivkey(argv[1], privkey, pubkey);
+        genprivkey(argv1.c_str(), privkey, pubkey);
         printf("private key: %s\n", privkey.getbuf());
         printf("public key: %s\n", pubkey.getbuf());
         return EXIT_SUCCESS;
     }
-    //Print yes/no to match pubkey with privkey: genkey <pubkey> <privkey>
-    else if(argc == 3)
-    {
+
+    // print yes/no to match pubkey with privkey: genkey <pubkey> <privkey>
+    if(argc == 3) {
         vector<char> pubkey;
         genpubkey(argv[2], pubkey);
-        printf("%s\n", !strcmp(argv[1], pubkey.getbuf()) ? "yes" : "no");
+        std::cerr << (argv1 == pubkey.data() ? "yes" : "no") << std::endl;
         return EXIT_SUCCESS;
     }
+
+    // fallback
+    std::cerr << "Error: unknown parameters, check " << argv[0] << " --help" << std::endl;
     return EXIT_FAILURE;
 }
-