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54 lines
2.0 KiB
54 lines
2.0 KiB
// Copyright 2019 The Chromium Authors. All rights reserved.
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// Use of this source code is governed by a BSD-style license that can be
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// found in the LICENSE file.
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#include "platform/api/time.h"
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#include <chrono>
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#include <ctime>
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#include "gtest/gtest.h"
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#include "util/chrono_helpers.h"
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namespace openscreen {
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#if __cplusplus < 202000L
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// Before C++20, the standard does not guarantee that time_t is the number of
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// seconds since the UNIX epoch. It also doesn't guarantee that one tick of
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// time_t represents one second. However, this is so universally common, it's
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// worth assuming the platform provides this.
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TEST(TimeTest, TimeTMeetsTheCpp20Standard) {
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// Use the functions the standard *does* provide for calendar time
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// conversions to determine the value of time_t at the UNIX epoch.
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std::tm epoch_tm;
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epoch_tm.tm_sec = 0;
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epoch_tm.tm_min = 0;
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epoch_tm.tm_hour = 0;
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epoch_tm.tm_mday = 1;
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epoch_tm.tm_mon = 0;
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epoch_tm.tm_year = 70; // 1970
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epoch_tm.tm_isdst = 0;
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// Note: std::mktime() assumes the translation is in the local time zone.
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const std::time_t new_year_1970_in_local_tz = std::mktime(&epoch_tm);
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// Purposely misinterpret |new_year_1970_in_local_tz| as UTC to provide
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// information as to how to offset |epoch_tm| such that std::mktime() will
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// be fooled into returning the value in terms of UTC.
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std::tm* const wrong_tm = std::gmtime(&new_year_1970_in_local_tz);
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epoch_tm.tm_sec += epoch_tm.tm_sec - wrong_tm->tm_sec;
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epoch_tm.tm_min += epoch_tm.tm_min - wrong_tm->tm_min;
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epoch_tm.tm_hour += epoch_tm.tm_hour - wrong_tm->tm_hour;
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epoch_tm.tm_mday += epoch_tm.tm_mday - wrong_tm->tm_mday;
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epoch_tm.tm_mon += epoch_tm.tm_mon - wrong_tm->tm_mon;
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epoch_tm.tm_year += epoch_tm.tm_year - wrong_tm->tm_year;
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const std::time_t epoch = std::mktime(&epoch_tm);
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EXPECT_EQ(seconds(0), seconds(epoch));
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++epoch_tm.tm_sec;
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const std::time_t epoch_plus_one_second = std::mktime(&epoch_tm);
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EXPECT_EQ(seconds(1), seconds(epoch_plus_one_second));
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}
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#endif
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} // namespace openscreen
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