vs2013 support

include/c11log/sinks/file_sinks.h

@@ -140,11 +140,14 @@ private:
         return system_clock::time_point(midnight + hours(24));
     }
 
+	//Create filename for the form basename.YYYY-MM-DD.extension
     static std::string _calc_filename(const std::string& basename, const std::string& extension) {
-        std::tm tm = c11log::details::os::localtime();
-        char buf[32];
-        sprintf(buf, ".%d-%02d-%02d.", tm.tm_year + 1900, tm.tm_mon + 1, tm.tm_mday);
-        return basename+buf+extension;
+        std::tm tm = c11log::details::os::localtime();		
+		std::ostringstream oss;
+		oss << basename << '.';
+		oss << tm.tm_year + 1900 << '-' << std::setw(2) << std::setfill('0') << tm.tm_mon + 1 << '-' << tm.tm_mday;
+		oss << '.' << extension;
+		return oss.str();
     }
 
     std::string _base_filename;

include/c11log/sinks/stdout_sinks.h

@@ -1,32 +1,40 @@
 #pragma once
 
 #include <iostream>
+#include <mutex>
+#include <memory>
+
 #include "base_sink.h"
 
 namespace c11log {
 namespace sinks {
 class ostream_sink: public base_sink {
 public:
-    ostream_sink(std::ostream& os):_ostream(os) {}
+    explicit ostream_sink(std::ostream& os):_ostream(os) {}
+	ostream_sink(const ostream_sink&) = delete;
+	ostream_sink& operator=(const ostream_sink&) = delete;
     virtual ~ostream_sink() = default;
 
 protected:
     virtual void _sink_it(const std::string& msg) override {
+		std::lock_guard<std::mutex> lock(_mutex);
         _ostream << msg;
     }
 
     std::ostream& _ostream;
+	std::mutex _mutex;
 };
 
-class stdout_sink:public ostream_sink {
-public:
-    stdout_sink():ostream_sink(std::cout) {}
-};
-
-class stderr_sink:public ostream_sink {
-public:
-    stderr_sink():ostream_sink(std::cerr) {}
-
-};
+inline std::shared_ptr<ostream_sink> cout_sink() {
+	static const ostream_sink& instance{std::cout};
+	return std::shared_ptr<ostream_sink>(&instance, [=](ostream_sink*) {});
+}
+
+inline std::shared_ptr<ostream_sink> cerr_sink() {
+	static const ostream_sink& instance = ostream_sink(std::cerr);
+	return std::shared_ptr<ostream_sink>(&instance, [=](ostream_sink*) {});
+}
+
+
+}
 }
-}