Add DiscreteClock and sources

src/ripple/algorithm/api/DiscreteClock.h

@@ -0,0 +1,106 @@
+//------------------------------------------------------------------------------
+/*
+    This file is part of rippled: https://github.com/ripple/rippled
+    Copyright (c) 2012, 2013 Ripple Labs Inc.
+
+    Permission to use, copy, modify, and/or distribute this software for any
+    purpose  with  or without fee is hereby granted, provided that the above
+    copyright notice and this permission notice appear in all copies.
+
+    THE  SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
+    WITH  REGARD  TO  THIS  SOFTWARE  INCLUDING  ALL  IMPLIED  WARRANTIES  OF
+    MERCHANTABILITY  AND  FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
+    ANY  SPECIAL ,  DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
+    WHATSOEVER  RESULTING  FROM  LOSS  OF USE, DATA OR PROFITS, WHETHER IN AN
+    ACTION  OF  CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
+    OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
+*/
+//==============================================================================
+
+#ifndef RIPPLE_ALGORITHM_DISCRETECLOCK_H_INCLUDED
+#define RIPPLE_ALGORITHM_DISCRETECLOCK_H_INCLUDED
+
+#include "beast/beast/StaticAssert.h"
+#include "beast/beast/type_traits/IsIntegral.h"
+#include "beast/beast/chrono/RelativeTime.h"
+
+namespace ripple {
+
+/** Interface for an elapsed time clock that uses integral units. */
+template <typename ElapsedType>
+class DiscreteClock
+{
+public:
+    /** Source of time for the discrete clock. */
+    class Source
+    {
+    public:
+        typedef ElapsedType elapsed_type;
+        typedef DiscreteClock <elapsed_type> DiscreteClockType;
+        virtual ElapsedType operator() () = 0;
+    };
+
+    /** Integral elapsed time type relative to an unspecified past event. */
+    typedef ElapsedType elapsed_type;
+
+    DiscreteClock (Source& source)
+        : m_source (source)
+    {
+        static_bassert (IsIntegral <elapsed_type>::value);
+    }
+
+    /** Returns the elapsed time in discrete units.
+        The elapsed time is relative to an unspecified event.
+    */
+    elapsed_type operator() () const
+    {
+        return m_source();
+    }
+
+private:
+    Source& m_source;
+};
+
+//------------------------------------------------------------------------------
+
+/** Seconds-based clock that uses elapsed time from startup as a time source. */
+class SimpleMonotonicClock : public DiscreteClock <int>::Source
+{
+public:
+    elapsed_type operator() ()
+    {
+        return static_cast <elapsed_type> (
+            RelativeTime::fromStartup().inSeconds());
+    }
+};
+
+//------------------------------------------------------------------------------
+
+/** A manually-operated clock.
+    This can be useful for unit tests.
+*/
+class ManualClock : public DiscreteClock <int>::Source
+{
+private:
+    elapsed_type m_now;
+
+public:
+    ManualClock ()
+        : m_now (elapsed_type())
+    {
+    }
+
+    elapsed_type& now()
+    {
+        return m_now;
+    }
+
+    elapsed_type operator() ()
+    {
+        return now();
+    }
+};
+
+}
+
+#endif