[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.

2 files changed, 35 insertions, 2 deletions

diff --git a/include/mbgl/storage/response.hpp b/include/mbgl/storage/response.hpp
index 8ab6170ba2..852110cb2a 100644
--- a/include/mbgl/storage/response.hpp
+++ b/include/mbgl/storage/response.hpp
@@ -1,6 +1,8 @@
 #ifndef MBGL_STORAGE_RESPONSE
 #define MBGL_STORAGE_RESPONSE
 
+#include <mbgl/util/chrono.hpp>
+
 #include <string>
 #include <memory>
 
@@ -25,8 +27,8 @@ public:
     // The actual data of the response. This is guaranteed to never be empty.
     std::shared_ptr<const std::string> data;
 
-    int64_t modified = 0;
-    int64_t expires = 0;
+    Seconds modified = Seconds::zero();
+    Seconds expires = Seconds::zero();
     std::string etag;
 };
 
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