time: add a period_limiter class

time.cpp

@@ -14,6 +14,7 @@
 
 using cruft::delta_clock;
 
+
 ///////////////////////////////////////////////////////////////////////////////
 static const uint64_t SECOND      = 1'000'000'000UL;
 static const uint64_t MILLISECOND =     1'000'000UL;
@@ -91,6 +92,32 @@ cruft::rate_limiter::poll (void)
 }
 
 
+///////////////////////////////////////////////////////////////////////////////
+cruft::period_limiter::period_limiter (std::chrono::nanoseconds _period)
+    : period_limiter (_period.count ())
+{ ; }
+
+
+//-----------------------------------------------------------------------------
+cruft::period_limiter::period_limiter (u64 _period)
+    : m_period (_period)
+    , m_prev   (nanoseconds () - _period)
+{ ; }
+
+
+//-----------------------------------------------------------------------------
+void cruft::period_limiter::poll (void)
+{
+    auto const now  = nanoseconds ();
+    auto const diff = now - m_prev;
+
+    if (diff < m_period)
+        sleep (m_period - diff);
+
+    m_prev = nanoseconds ();
+}
+
+
 ///////////////////////////////////////////////////////////////////////////////
 cruft::polled_duration::polled_duration (std::string name, uint64_t interval):
     m_name     (std::move (name)),

time.hpp

@@ -3,12 +3,13 @@
  * License, v. 2.0. If a copy of the MPL was not distributed with this
  * file, You can obtain one at http://mozilla.org/MPL/2.0/.
  *
- * Copyright 2010-2016 Danny Robson <danny@nerdcruft.net>
+ * Copyright 2010-2016, 2022 Danny Robson <danny@nerdcruft.net>
  */
 
 #pragma once
 
-#include "stats.hpp"
+#include "./std.hpp"
+#include "./stats.hpp"
 
 #include <chrono>
 #include <cstdint>
@@ -75,6 +76,20 @@ namespace cruft {
     };
 
 
+    ///////////////////////////////////////////////////////////////////////////
+    class period_limiter {
+    public:
+        explicit period_limiter (std::chrono::nanoseconds _period);
+        explicit period_limiter (u64);
+
+        void poll (void);
+
+    private:
+        u64 m_period;
+        u64 m_prev;
+    };
+
+
     ///////////////////////////////////////////////////////////////////////////
     class polled_duration {
         public: