1 // Copyright 2019 The Chromium Authors. All rights reserved. 2 // Use of this source code is governed by a BSD-style license that can be 3 // found in the LICENSE file. 4 5 #include "platform/api/time.h" 6 7 #include <chrono> 8 #include <ctime> 9 10 #include "gtest/gtest.h" 11 #include "util/chrono_helpers.h" 12 13 namespace openscreen { 14 15 #if __cplusplus < 202000L 16 // Before C++20, the standard does not guarantee that time_t is the number of 17 // seconds since the UNIX epoch. It also doesn't guarantee that one tick of 18 // time_t represents one second. However, this is so universally common, it's 19 // worth assuming the platform provides this. TEST(TimeTest,TimeTMeetsTheCpp20Standard)20TEST(TimeTest, TimeTMeetsTheCpp20Standard) { 21 // Use the functions the standard *does* provide for calendar time 22 // conversions to determine the value of time_t at the UNIX epoch. 23 std::tm epoch_tm; 24 epoch_tm.tm_sec = 0; 25 epoch_tm.tm_min = 0; 26 epoch_tm.tm_hour = 0; 27 epoch_tm.tm_mday = 1; 28 epoch_tm.tm_mon = 0; 29 epoch_tm.tm_year = 70; // 1970 30 epoch_tm.tm_isdst = 0; 31 // Note: std::mktime() assumes the translation is in the local time zone. 32 const std::time_t new_year_1970_in_local_tz = std::mktime(&epoch_tm); 33 // Purposely misinterpret |new_year_1970_in_local_tz| as UTC to provide 34 // information as to how to offset |epoch_tm| such that std::mktime() will 35 // be fooled into returning the value in terms of UTC. 36 std::tm* const wrong_tm = std::gmtime(&new_year_1970_in_local_tz); 37 epoch_tm.tm_sec += epoch_tm.tm_sec - wrong_tm->tm_sec; 38 epoch_tm.tm_min += epoch_tm.tm_min - wrong_tm->tm_min; 39 epoch_tm.tm_hour += epoch_tm.tm_hour - wrong_tm->tm_hour; 40 epoch_tm.tm_mday += epoch_tm.tm_mday - wrong_tm->tm_mday; 41 epoch_tm.tm_mon += epoch_tm.tm_mon - wrong_tm->tm_mon; 42 epoch_tm.tm_year += epoch_tm.tm_year - wrong_tm->tm_year; 43 44 const std::time_t epoch = std::mktime(&epoch_tm); 45 EXPECT_EQ(seconds(0), seconds(epoch)); 46 47 ++epoch_tm.tm_sec; 48 const std::time_t epoch_plus_one_second = std::mktime(&epoch_tm); 49 EXPECT_EQ(seconds(1), seconds(epoch_plus_one_second)); 50 } 51 #endif 52 53 } // namespace openscreen 54