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58 lines
1.8 KiB
58 lines
1.8 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 <thread>
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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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namespace {
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// Tests that the clock always seems to tick forward. If this test is broken, or
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// is flaky, the time source is probably not monotonic.
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TEST(TimeTest, PlatformClockIsMonotonic) {
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constexpr auto kSleepPeriod = milliseconds(2);
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for (int i = 0; i < 50; ++i) {
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const auto start = Clock::now();
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std::this_thread::sleep_for(kSleepPeriod);
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const auto stop = Clock::now();
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EXPECT_GE(stop - start, kSleepPeriod / 2);
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}
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}
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// Tests that the clock ticks at least 10000 times per second, a requirement
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// specified in the API header comments.
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TEST(TimeTest, PlatformClockHasSufficientResolution) {
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constexpr std::chrono::duration<int, Clock::kRequiredResolution>
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kMaxAllowedDurationBetweenTicks(1);
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constexpr int kMaxRetries = 100;
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// Loop until a small-enough clock change is observed. The platform is given
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// multiple chances because unpredictable events, like thread context
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// switches, could suspend the current thread for a "long" time, masking what
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// the clock is actually capable of.
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Clock::duration delta = microseconds(0);
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for (int i = 0; i < kMaxRetries; ++i) {
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const auto start = Clock::now();
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// Loop until the clock changes.
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do {
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delta = Clock::now() - start;
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ASSERT_LE(microseconds(0), delta);
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} while (delta == microseconds(0));
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if (delta <= kMaxAllowedDurationBetweenTicks) {
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break;
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}
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}
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EXPECT_LE(delta, kMaxAllowedDurationBetweenTicks);
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}
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} // namespace
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} // namespace openscreen
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