text: // Copyright 2014 The Crashpad Authors. All rights reserved.
  //
  // Licensed under the Apache License, Version 2.0 (the "License");
  // you may not use this file except in compliance with the License.
  // You may obtain a copy of the License at
  //
  //     http://www.apache.org/licenses/LICENSE-2.0
  //
  // Unless required by applicable law or agreed to in writing, software
  // distributed under the License is distributed on an "AS IS" BASIS,
  // WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
  // See the License for the specific language governing permissions and
  // limitations under the License.
  
  #include "util/misc/clock.h"
  
  #include <stdint.h>
  
  #include <algorithm>
  
  #include "base/basictypes.h"
  #include "base/logging.h"
  #include "base/strings/stringprintf.h"
  #include "gtest/gtest.h"
  
  namespace crashpad {
  namespace test {
  namespace {
  
  TEST(Clock, ClockMonotonicNanoseconds) {
    uint64_t start = ClockMonotonicNanoseconds();
    EXPECT_GT(start, 0u);
  
    uint64_t now = start;
    for (size_t iteration = 0; iteration < 10; ++iteration) {
      uint64_t last = now;
      now = ClockMonotonicNanoseconds();
  
      // Use EXPECT_GE instead of EXPECT_GT, because there are no guarantees about
      // the clock’s resolution.
      EXPECT_GE(now, last);
    }
  
  #if !defined(OS_WIN)  // No SleepNanoseconds implemented on Windows.
    // SleepNanoseconds() should sleep for at least the value of the clock’s
    // resolution, so the clock’s value should definitely increase after a sleep.
    // EXPECT_GT can be used instead of EXPECT_GE after the sleep.
    SleepNanoseconds(1);
    now = ClockMonotonicNanoseconds();
    EXPECT_GT(now, start);
  #endif  // OS_WIN
  }
  
  #if !defined(OS_WIN)  // No SleepNanoseconds implemented on Windows.
  
  void TestSleepNanoseconds(uint64_t nanoseconds) {
    uint64_t start = ClockMonotonicNanoseconds();
  
    SleepNanoseconds(nanoseconds);
  
    uint64_t end = ClockMonotonicNanoseconds();
    uint64_t diff = end - start;
  
    // |nanoseconds| is the lower bound for the actual amount of time spent
    // sleeping.
    EXPECT_GE(diff, nanoseconds);
  
    // It’s difficult to set an upper bound for the time spent sleeping, and
    // attempting to do so results in a flaky test.
  }
  
  TEST(Clock, SleepNanoseconds) {
    const uint64_t kTestData[] = {
        0,
        1,
        static_cast<uint64_t>(1E3),  // 1 microsecond
        static_cast<uint64_t>(1E4),  // 10 microseconds
        static_cast<uint64_t>(1E5),  // 100 microseconds
        static_cast<uint64_t>(1E6),  // 1 millisecond
        static_cast<uint64_t>(1E7),  // 10 milliseconds
        static_cast<uint64_t>(2E7),  // 20 milliseconds
        static_cast<uint64_t>(5E7),  // 50 milliseconds
    };
  
    for (size_t index = 0; index < arraysize(kTestData); ++index) {
      const uint64_t nanoseconds = kTestData[index];
      SCOPED_TRACE(
          base::StringPrintf("index %zu, nanoseconds %llu", index, nanoseconds));
  
      TestSleepNanoseconds(nanoseconds);
    }
  }
  
  #endif  // OS_WIN
  
  }  // namespace
  }  // namespace test
  }  // namespace crashpad
  