Add time_t to w3c time format converter and from time_t to w3c time converter as well.

base/base_tests/base_tests.pro

@@ -39,5 +39,6 @@ SOURCES += \
   threads_test.cpp \
   timer_test.cpp \
   worker_thread_test.cpp \
+  w3ctime_test.cpp \
 
 HEADERS +=

base/base_tests/w3ctime_test.cpp

@@ -0,0 +1,17 @@
+#include "base/w3ctime.hpp"
+#include "testing/testing.hpp"
+
+using namespace w3ctime;
+
+UNIT_TEST(ParseTime)
+{
+  TEST_EQUAL(ParseTime(""), kNotATime, ());
+  TEST_EQUAL(ParseTime("2015-10-11 23:21"), kNotATime, ());
+  TEST_EQUAL(ParseTime("2015-10-11T23:21Z"), 1444605660, ());
+}
+
+UNIT_TEST(TimeToString)
+{
+  TEST_EQUAL(TimeToString(0), "1970-01-01T00:00Z", ());
+  TEST_EQUAL(TimeToString(1444605660), "2015-10-11T23:21Z", ());
+}

base/w3ctime.hpp

@@ -0,0 +1,44 @@
+#pragma once
+
+#include "std/array.hpp"
+#include "std/ctime.hpp"
+#include "std/string.hpp"
+
+// It would be better to use c++ standard means of
+// time parsing and unparsing like
+// time_get/time_put (<locale>) or get_time/put_time (<iomanip>).
+// But at the moment of writing they was not widely supporded
+// and/or worked inkorekd.
+//
+// All covertions are made in UTC
+
+namespace w3ctime
+{
+char constexpr kW3CTimeFormat[] = "%Y-%m-%dT%H:%MZ";
+
+// Two more digits for year and one for \n
+size_t constexpr kBufSize = sizeof(kW3CTimeFormat) + 2 + 1;
+
+time_t constexpr kNotATime = -1;
+
+inline time_t ParseTime(std::string const & w3ctime) noexcept
+{
+  std::tm tm{};
+  if (strptime(w3ctime.data(), kW3CTimeFormat, &tm) == nullptr)
+    return kNotATime;
+
+  return timegm(&tm);
+}
+
+inline std::string TimeToString(time_t const timestamp) noexcept
+{
+  std::tm tm{};
+  array<char, kBufSize> buff{};
+
+  gmtime_r(&timestamp, &tm);
+  strftime(buff.data(), kBufSize, kW3CTimeFormat, &tm);
+
+  return buff.data();
+}
+
+} // namespace w3ctime