X-Git-Url: http://plrg.eecs.uci.edu/git/?a=blobdiff_plain;f=folly%2FChrono.h;h=852a74b7f6d96ae877446056cdeb44dc79b9f814;hb=79b78eaaf88ead9fa6543822c193b4e86d0e2395;hp=1a9dfa54631285b7e2e3dac540f5fcf15054c7ca;hpb=22afce906d7e98d95f8c45c3301072d9fd891d41;p=folly.git

diff --git a/folly/Chrono.h b/folly/Chrono.h
index 1a9dfa54..852a74b7 100644
--- a/folly/Chrono.h
+++ b/folly/Chrono.h
@@ -1,5 +1,5 @@
 /*
- * Copyright 2014 Facebook, Inc.
+ * Copyright 2017 Facebook, Inc.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -14,20 +14,141 @@
  * limitations under the License.
  */
 
-// Wrapper around <chrono> that hides away some gcc 4.6 issues
-#ifndef FOLLY_CHRONO_H_
-#define FOLLY_CHRONO_H_
+#pragma once
 
 #include <chrono>
-#include "folly/Portability.h"
-
-// gcc 4.6 uses an obsolete name for steady_clock, although the implementation
-// is the same
-#if __GNUC_PREREQ(4, 6) && !__GNUC_PREREQ(4, 7)
-namespace std { namespace chrono {
-typedef monotonic_clock steady_clock;
-}}  // namespaces
-#endif
+#include <type_traits>
+
+/***
+ *  include or backport:
+ *  * std::chrono::ceil
+ *  * std::chrono::floor
+ *  * std::chrono::round
+ */
+
+#if __cpp_lib_chrono >= 201510 || _MSC_VER
+
+namespace folly {
+namespace chrono {
+
+/* using override */ using std::chrono::ceil;
+/* using override */ using std::chrono::floor;
+/* using override */ using std::chrono::round;
+}
+}
+
+#else
+
+namespace folly {
+namespace chrono {
+
+namespace detail {
+
+//  from: http://en.cppreference.com/w/cpp/chrono/duration/ceil, CC-BY-SA
+template <typename T>
+struct is_duration : std::false_type {};
+template <typename Rep, typename Period>
+struct is_duration<std::chrono::duration<Rep, Period>> : std::true_type {};
+
+template <typename To, typename Duration>
+constexpr To ceil_impl(Duration const& d, To const& t) {
+  return t < d ? t + To{1} : t;
+}
 
-#endif /* FOLLY_CHRONO_H_ */
+template <typename To, typename Duration>
+constexpr To floor_impl(Duration const& d, To const& t) {
+  return t > d ? t - To{1} : t;
+}
 
+template <typename To, typename Diff>
+constexpr To round_impl(To const& t0, To const& t1, Diff diff0, Diff diff1) {
+  return diff0 < diff1 ? t0 : diff1 < diff0 ? t1 : t0.count() & 1 ? t1 : t0;
+}
+
+template <typename To, typename Duration>
+constexpr To round_impl(Duration const& d, To const& t0, To const& t1) {
+  return round_impl(t0, t1, d - t0, t1 - d);
+}
+
+template <typename To, typename Duration>
+constexpr To round_impl(Duration const& d, To const& t0) {
+  return round_impl(d, t0, t0 + To{1});
+}
+}
+
+//  mimic: std::chrono::ceil, C++17
+//  from: http://en.cppreference.com/w/cpp/chrono/duration/ceil, CC-BY-SA
+template <
+    typename To,
+    typename Rep,
+    typename Period,
+    typename = typename std::enable_if<detail::is_duration<To>::value>::type>
+constexpr To ceil(std::chrono::duration<Rep, Period> const& d) {
+  return detail::ceil_impl(d, std::chrono::duration_cast<To>(d));
+}
+
+//  mimic: std::chrono::ceil, C++17
+//  from: http://en.cppreference.com/w/cpp/chrono/time_point/ceil, CC-BY-SA
+template <
+    typename To,
+    typename Clock,
+    typename Duration,
+    typename = typename std::enable_if<detail::is_duration<To>::value>::type>
+constexpr std::chrono::time_point<Clock, To> ceil(
+    std::chrono::time_point<Clock, Duration> const& tp) {
+  return std::chrono::time_point<Clock, To>{ceil<To>(tp.time_since_epoch())};
+}
+
+//  mimic: std::chrono::floor, C++17
+//  from: http://en.cppreference.com/w/cpp/chrono/duration/floor, CC-BY-SA
+template <
+    typename To,
+    typename Rep,
+    typename Period,
+    typename = typename std::enable_if<detail::is_duration<To>::value>::type>
+constexpr To floor(std::chrono::duration<Rep, Period> const& d) {
+  return detail::floor_impl(d, std::chrono::duration_cast<To>(d));
+}
+
+//  mimic: std::chrono::floor, C++17
+//  from: http://en.cppreference.com/w/cpp/chrono/time_point/floor, CC-BY-SA
+template <
+    typename To,
+    typename Clock,
+    typename Duration,
+    typename = typename std::enable_if<detail::is_duration<To>::value>::type>
+constexpr std::chrono::time_point<Clock, To> floor(
+    std::chrono::time_point<Clock, Duration> const& tp) {
+  return std::chrono::time_point<Clock, To>{floor<To>(tp.time_since_epoch())};
+}
+
+//  mimic: std::chrono::round, C++17
+//  from: http://en.cppreference.com/w/cpp/chrono/duration/round, CC-BY-SA
+template <
+    typename To,
+    typename Rep,
+    typename Period,
+    typename = typename std::enable_if<
+        detail::is_duration<To>::value &&
+        !std::chrono::treat_as_floating_point<typename To::rep>::value>::type>
+constexpr To round(std::chrono::duration<Rep, Period> const& d) {
+  return detail::round_impl(d, floor<To>(d));
+}
+
+//  mimic: std::chrono::round, C++17
+//  from: http://en.cppreference.com/w/cpp/chrono/time_point/round, CC-BY-SA
+template <
+    typename To,
+    typename Clock,
+    typename Duration,
+    typename = typename std::enable_if<
+        detail::is_duration<To>::value &&
+        !std::chrono::treat_as_floating_point<typename To::rep>::value>::type>
+constexpr std::chrono::time_point<Clock, To> round(
+    std::chrono::time_point<Clock, Duration> const& tp) {
+  return std::chrono::time_point<Clock, To>{round<To>(tp.time_since_epoch())};
+}
+}
+}
+
+#endif