added timezone support

CMakeLists.txt

@@ -3,10 +3,35 @@ cmake_minimum_required(VERSION 3.6)
 project(top)
 
 option(LIBCRON_BUILD_TZ_CLOCK "Build timezone clock" OFF)
+option(LIBCRON_MANUAL_TZ_DB "User will set TZ DB manually by invoking date::set_install in their code" OFF)
 
 if(LIBCRON_BUILD_TZ_CLOCK)
-    set(BUILD_TZ_LIB ON CACHE BOOL "Build the tz library" FORCE)
-    add_subdirectory(libcron/externals/date)
+    add_library(date-tz)
+    target_sources(date-tz
+      PUBLIC
+        ${CMAKE_CURRENT_SOURCE_DIR}/libcron/externals/date/include/date/tz.h
+      PRIVATE
+        ${CMAKE_CURRENT_SOURCE_DIR}/libcron/externals/date/include/date/tz_private.h
+        ${CMAKE_CURRENT_LIST_DIR}/libcron/externals/date/src/tz.cpp
+    )
+    target_include_directories(date-tz PUBLIC ${CMAKE_CURRENT_SOURCE_DIR}/libcron/externals/date/include)
+
+    if (LIBCRON_MANUAL_TZ_DB)
+        target_compile_definitions(date-tz PRIVATE AUTO_DOWNLOAD=0 HAS_REMOTE_API=0)
+    else()
+        find_package(CURL REQUIRED)
+        target_link_libraries(date-tz PRIVATE CURL::libcurl)
+        target_compile_definitions(date-tz PRIVATE AUTO_DOWNLOAD=1 HAS_REMOTE_API=1)
+    endif()
+
+    if (WIN32 AND BUILD_SHARED_LIBS)
+        target_compile_definitions(date-tz PUBLIC DATE_BUILD_DLL=1)
+    endif()
+
+    if(NOT MSVC)
+        find_package(Threads)
+        target_link_libraries(date-tz PUBLIC Threads::Threads)
+    endif()
 endif()
 
 add_subdirectory(libcron)

README.md

@@ -149,14 +149,14 @@ else
 If you want to use TzClock you have to set -DLIBCRON_BUILD_TZ_CLOCK=ON when building libcron. TzClock is a fully optional feature
 if you don't enable it, it won't be build at all.
 
-Using TzClock has the following side effects:
-  1. Date requires linkage to `libcurl`
-  2. First time TzClocks timezone lookup will occur it will download the most up to date timezone: "~/Downloads/tzdata" ("%homedrive%\%homepath%\downloads\tzdata" on Windows).
-  3. TzClock uses a `std::mutex` to protect the time zone in multithreaded envoirements.
-  4. This implementation might decrease performance a lot based on point 2 and 3.
+By default when setting the time zone with `TzClock::set_time_zone`, date-tz will automatically download the neweset database version from [Time Zones](https://www.iana.org/time-zones).
+This can be disabled with `-DLIBCRON_MANUAL_TZ_DB=ON`. If this is set user will be responsible of downloading timezone database.
 
-[More Info about date-tz](https://howardhinnant.github.io/date/tz.html)
+Setting database path / install path can be done with `date::set_install`. If not set path will default to: "~/Downloads/tzdata" ("%homedrive%\%homepath%\downloads\tzdata" on Windows).
+Using TzClock without LIBCRON_MANUAL_TZ_DB requires liburl installed in your system. On Windows it will also require 7-Zip installed into the default location.
+TzClock by default protects it's time_zone with a `std::mutex` this can be disabled by setting LockType to libcron::NullLock.
 
+[More Info about date-tz](https://howardhinnant.github.io/date/tz.html)
 [Available Regions](https://en.wikipedia.org/wiki/List_of_tz_database_time_zones)
 
 # Supported formatting

libcron/include/libcron/CronClock.h

@@ -45,6 +45,7 @@ namespace libcron
     };
 
 #ifdef BUILD_TZ_CLOCK
+    template<typename LockType = std::mutex>
     class TzClock : public ICronClock
     {
         public:
@@ -54,10 +55,34 @@ namespace libcron
                 return now + utc_offset(now);
             }
 
-            bool set_time_zone(std::string_view tz_name);
-            std::chrono::seconds utc_offset(std::chrono::system_clock::time_point now) const override;
+            std::chrono::seconds utc_offset(std::chrono::system_clock::time_point now) const override
+            {
+                // If we don't have a timezone we use utc
+                using namespace std::chrono;
+                std::lock_guard<LockType> lock(time_zone_mtx);
+                if (time_zone)
+                    return time_zone->get_info(now).offset;
+                else
+                    return 0s;
+            }
+
+            bool set_time_zone(std::string_view tz_name)
+            {
+                const date::time_zone *new_zone{nullptr};
+                try
+                {
+                    new_zone = date::locate_zone(tz_name);
+                }
+                catch (std::runtime_error &err)
+                {
+                    return false;
+                }
+                std::lock_guard<LockType> lock(time_zone_mtx);
+                time_zone = new_zone;
+                return true;
+            }
         private:
-            mutable std::mutex time_zone_mtx{};
+            mutable LockType time_zone_mtx{};
             const date::time_zone* time_zone{nullptr};
     };
 #endif

libcron/src/CronClock.cpp

@@ -36,35 +36,4 @@ namespace libcron
 #endif
 		return offset;
 	}
-
-#ifdef BUILD_TZ_CLOCK
-	bool TzClock::set_time_zone(std::string_view tz_name)
-	{
-		const date::time_zone *new_zone{nullptr};
-
-		try
-		{
-			new_zone = date::locate_zone(tz_name);
-		}
-		catch (std::runtime_error &err)
-		{
-			return false;
-		}
-
-		std::lock_guard<std::mutex> lock(time_zone_mtx);
-		time_zone = new_zone;
-		return true;
-	}
-
-	std::chrono::seconds TzClock::utc_offset(std::chrono::system_clock::time_point now) const
-	{
-		using namespace std::chrono;
-		// If we don't have a timezone we use utc
-		std::lock_guard<std::mutex> lock(time_zone_mtx);
-		if (time_zone)
-			return time_zone->get_info(now).offset;
-		else
-			return 0s;
-	}
-#endif
 }