rng: static initialisation of hasRdrand()

include/opendht/rng.h

@@ -68,7 +68,7 @@ public:
     }
 
     double entropy() const {
-        if (has_rdrand or has_rdseed)
+        if (hasRdrand() or hasRdseed())
             return 1.;
         return 0.;
     }
@@ -76,11 +76,21 @@ public:
 private:
     random_device& operator=(random_device&) = delete;
 
-    const bool has_rdrand;
-    const bool has_rdseed;
     pseudo_engine gen;
     std::uniform_int_distribution<result_type> dis {};
 
+    static bool hasIntelCpu();
+    static bool hasRdrand() {
+        static const bool hasrdrand = _hasRdrand();
+        return hasrdrand;
+    }
+    static bool hasRdseed() {
+        static const bool hasrdseed = _hasRdseed();
+        return hasrdseed;
+    }
+    static bool _hasRdrand();
+    static bool _hasRdseed();
+
     struct CPUIDinfo {
         unsigned int EAX;
         unsigned int EBX;
@@ -88,9 +98,6 @@ private:
         unsigned int EDX;
         void get(const unsigned int func, const unsigned int subfunc);
     };
-    static bool hasIntelCpu();
-    static bool hasRdrand();
-    static bool hasRdseed();
     bool rdrandStep(result_type* r);
     bool rdrand(result_type* r);
     bool rdseedStep(result_type* r);

src/rng.cpp

@@ -37,8 +37,6 @@ namespace dht {
 namespace crypto {
 
 random_device::random_device() :
-   has_rdrand(hasRdrand()),
-   has_rdseed(hasRdseed()),
    gen(std::chrono::system_clock::now().time_since_epoch().count())
 {}
 
@@ -47,9 +45,9 @@ random_device::operator()()
 {
     result_type prand = dis(gen);
     result_type hwrand;
-    if (has_rdseed and rdseed(&hwrand))
+    if (hasRdseed() and rdseed(&hwrand))
         prand ^= hwrand;
-    else if (has_rdrand and rdrand(&hwrand))
+    else if (hasRdrand() and rdrand(&hwrand))
         prand ^= hwrand;
     return prand;
 }
@@ -78,7 +76,7 @@ random_device::hasIntelCpu()
 }
 
 bool
-random_device::hasRdrand()
+random_device::_hasRdrand()
 {
     if (!hasIntelCpu())
         return false;
@@ -92,7 +90,7 @@ random_device::hasRdrand()
 }
 
 bool
-random_device::hasRdseed()
+random_device::_hasRdseed()
 {
     if (!hasIntelCpu())
         return false;