[core] Replace time_t with std::chrono::seconds

Added aliases for std::chrono typedefs (eg. 'Seconds' for
std::chrono::seconds). These aliases are used together with templated
helper functions to replace time_t with std::chrono::seconds for most
cases, in particular for 'modified' and 'expires' values in Response.

1 files changed, 31 insertions, 0 deletions

diff --git a/include/mbgl/util/chrono.hpp b/include/mbgl/util/chrono.hpp
index df8c5e6234..9c99c7bcdf 100644
--- a/include/mbgl/util/chrono.hpp
+++ b/include/mbgl/util/chrono.hpp
@@ -8,9 +8,40 @@ namespace mbgl {
 using Clock = std::chrono::steady_clock;
 using SystemClock = std::chrono::system_clock;
 
+using Seconds = std::chrono::seconds;
+using Milliseconds = std::chrono::milliseconds;
+
 using TimePoint = Clock::time_point;
 using Duration  = Clock::duration;
 
+using SystemTimePoint = SystemClock::time_point;
+using SystemDuration = SystemClock::duration;
+
+template <class _Clock, class _Duration>
+_Duration toDuration(std::chrono::time_point<_Clock, _Duration> time_point) {
+    return time_point.time_since_epoch();
+}
+
+template <class _Duration>
+Seconds asSeconds(_Duration duration) {
+    return std::chrono::duration_cast<Seconds>(duration);
+}
+
+template <class _Clock, class _Duration>
+Seconds toSeconds(std::chrono::time_point<_Clock, _Duration> time_point) {
+    return asSeconds(toDuration<_Clock, _Duration>(time_point));
+}
+
+template <class _Duration>
+Milliseconds asMilliseconds(_Duration duration) {
+    return std::chrono::duration_cast<Milliseconds>(duration);
+}
+
+template <class _Clock, class _Duration>
+Milliseconds toMilliseconds(std::chrono::time_point<_Clock, _Duration> time_point) {
+    return asMilliseconds(toDuration<_Clock, _Duration>(time_point));
+}
+
 }
 
 #endif