epee: allow a random component in once_a_time timeouts

contrib/epee/include/math_helper.h

@@ -32,6 +32,7 @@
 
 #include <list>
 #include <numeric>
+#include <random>
 #include <boost/timer/timer.hpp>
 #include <boost/uuid/uuid.hpp>
 #include <boost/uuid/random_generator.hpp>
@@ -230,7 +231,7 @@ namespace math_helper
 		}
 
 	}
-	template<uint64_t scale, int default_interval, bool start_immediate = true>
+	template<typename get_interval, bool start_immediate = true>
 	class once_a_time
 	{
     uint64_t get_time() const
@@ -251,12 +252,18 @@ namespace math_helper
 #endif
     }
 
+    void set_next_interval()
+    {
+      m_interval = get_interval()();
+    }
+
 	public:
-		once_a_time():m_interval(default_interval * scale)
+		once_a_time()
 		{
 			m_last_worked_time = 0;
       if(!start_immediate)
         m_last_worked_time = get_time();
+      set_next_interval();
 		}
 
     void trigger()
@@ -273,6 +280,7 @@ namespace math_helper
 			{
 				bool res = functr();
 				m_last_worked_time = get_time();
+        set_next_interval();
 				return res;
 			}
 			return true;
@@ -283,9 +291,13 @@ namespace math_helper
 		uint64_t m_interval;
 	};
 
+  template<uint64_t N> struct get_constant_interval { public: uint64_t operator()() const { return N; } };
+
   template<int default_interval, bool start_immediate = true>
-  class once_a_time_seconds: public once_a_time<1000000, default_interval, start_immediate> {};
+  class once_a_time_seconds: public once_a_time<get_constant_interval<default_interval * (uint64_t)1000000>, start_immediate> {};
   template<int default_interval, bool start_immediate = true>
-  class once_a_time_milliseconds: public once_a_time<1000, default_interval, start_immediate> {};
+  class once_a_time_milliseconds: public once_a_time<get_constant_interval<default_interval * (uint64_t)1000>, start_immediate> {};
+  template<typename get_interval, bool start_immediate = true>
+  class once_a_time_seconds_range: public once_a_time<get_interval, start_immediate> {};
 }
 }