Improve random engine entropy and clean up random engine initialization

application/application.cpp

@@ -321,7 +321,7 @@ int eu07_application::init(int Argc, char *Argv[])
 	}
 
 	if (!Global.random_seed)
-		Global.random_seed = clock_seed();
+		Global.random_seed = true_random_seed();
 	Global.random_engine.seed(Global.random_seed);
 
 	// configure the OS console according to Globals.ShowSystemConsole.
@@ -1432,7 +1432,7 @@ int eu07_application::init_data()
 
 int eu07_application::init_modes()
 {
-	Global.local_random_engine.seed(clock_seed());
+	Global.local_random_engine.seed(true_random_seed());
 
 	if ((!Global.network_servers.empty() || Global.network_client) && Global.SceneryFile.empty())
 	{

utilities/utilities.cpp

@@ -138,10 +138,20 @@ int Random(int min, int max)
 	return dist(Global.random_engine);
 }
 
-std::uint32_t clock_seed()
+std::uint64_t true_random_seed()
 {
-	static std::atomic<std::uint32_t> nth{0};
+	try
-	return static_cast<std::uint32_t>(std::time({})) + nth.fetch_add(1, std::memory_order_relaxed);
+	{
+		std::random_device rd;
+		if (rd.entropy()  > 0.0)
+		{
+			std::uint32_t high = rd();
+			std::uint32_t low = rd();
+			return (high << 32) | low;
+		}
+	}
+	catch (...) {}
+	return static_cast<std::uint64_t>(std::chrono::high_resolution_clock::now().time_since_epoch().count());
 }
 
 std::uint32_t seed_of(std::string const &Text)
@@ -161,12 +171,11 @@ std::uint32_t seed_of(std::string const &Text)
 
 std::string generate_uuid_v4()
 {
-	static thread_local std::mt19937 generator{clock_seed()};
 	std::uniform_int_distribution<int> dist(0, 255);
 
 	std::array<uint8_t, 16> bytes;
 	for (auto &b : bytes)
-		b = static_cast<uint8_t>(dist(generator));
+		b = static_cast<uint8_t>(dist(Global.random_engine));
 
 	// UUID v4 (RFC 4122)
 	bytes[6] = bytes[6] & 0x0F | 0x40;

utilities/utilities.h

@@ -63,9 +63,10 @@ inline long Round(double const f)
 double Random(double a, double b);
 int Random(int min, int max);
 
-// Seed for the random engines: the clock, plus a counter so two engines seeded in
+/// @author lxvia
-// the same second do not come out the same.
+/// @brief Returns a random seed from the system's entropy source, if available. Otherwise, falls back to a clock-based seed.
-std::uint32_t clock_seed();
+/// @return A random seed as 64 bit unsigned integer
+std::uint64_t true_random_seed();
 
 // The seed a word stands for. A number is taken as it is written; anything else is
 // hashed the way Java's String.hashCode does it, so the same word gives the same

utilities/uuid.hpp

@@ -7,6 +7,7 @@
 #include <algorithm>
 #include <cstdint>
 #include "utilities/utilities.h"
+#include "utilities/Globals.h"
 
 class UID {
 public:
@@ -14,10 +15,9 @@ public:
 
 
     static UID random() {
-        static thread_local std::mt19937_64 gen{clock_seed()};
         UID u;
-        uint64_t a = gen();
+        uint64_t a = Global.random_engine();
-        uint64_t b = gen();
+        uint64_t b = Global.random_engine();
         for (int i = 0; i < 8; ++i) u.bytes[i] = uint8_t(a >> (i * 8) & 0xFF);
         for (int i = 0; i < 8; ++i) u.bytes[8 + i] = uint8_t(b >> (i * 8) & 0xFF);