1 // Copyright 2018 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 #ifndef BASE_TIME_TIME_OVERRIDE_H_ 6 #define BASE_TIME_TIME_OVERRIDE_H_ 7 8 #include "base/base_export.h" 9 #include "base/time/time.h" 10 11 namespace base { 12 13 using TimeNowFunction = decltype(&Time::Now); 14 using TimeTicksNowFunction = decltype(&TimeTicks::Now); 15 using ThreadTicksNowFunction = decltype(&ThreadTicks::Now); 16 17 // Time overrides should be used with extreme caution. Discuss with //base/time 18 // OWNERS before adding a new one. 19 namespace subtle { 20 21 // Override the return value of Time::Now and Time::NowFromSystemTime / 22 // TimeTicks::Now / ThreadTicks::Now to emulate time, e.g. for tests or to 23 // modify progression of time. Note that the override should be set while 24 // single-threaded and before the first call to Now() to avoid threading issues 25 // and inconsistencies in returned values. Nested overrides are not allowed. 26 class BASE_EXPORT ScopedTimeClockOverrides { 27 public: 28 // Pass |nullptr| for any override if it shouldn't be overriden. 29 ScopedTimeClockOverrides(TimeNowFunction time_override, 30 TimeTicksNowFunction time_ticks_override, 31 ThreadTicksNowFunction thread_ticks_override); 32 33 // Restores the platform default Now() functions. 34 ~ScopedTimeClockOverrides(); 35 36 private: 37 #if DCHECK_IS_ON() 38 static bool overrides_active_; 39 #endif 40 41 DISALLOW_IMPLICIT_CONSTRUCTORS(ScopedTimeClockOverrides); 42 }; 43 44 // These methods return the platform default Time::Now / TimeTicks::Now / 45 // ThreadTicks::Now values even while an override is in place. These methods 46 // should only be used in places where emulated time should be disregarded. For 47 // example, they can be used to implement test timeouts for tests that may 48 // override time. 49 BASE_EXPORT Time TimeNowIgnoringOverride(); 50 BASE_EXPORT Time TimeNowFromSystemTimeIgnoringOverride(); 51 BASE_EXPORT TimeTicks TimeTicksNowIgnoringOverride(); 52 BASE_EXPORT ThreadTicks ThreadTicksNowIgnoringOverride(); 53 54 } // namespace subtle 55 56 namespace internal { 57 58 // These function pointers are used by platform-independent implementations of 59 // the Now() methods and ScopedTimeClockOverrides. They are set to point to the 60 // respective NowIgnoringOverride functions by default, but can also be set by 61 // platform-specific code to select a default implementation at runtime, thereby 62 // avoiding the indirection via the NowIgnoringOverride functions. Note that the 63 // pointers can be overridden and later reset to the NowIgnoringOverride 64 // functions by ScopedTimeClockOverrides. 65 extern TimeNowFunction g_time_now_function; 66 extern TimeNowFunction g_time_now_from_system_time_function; 67 extern TimeTicksNowFunction g_time_ticks_now_function; 68 extern ThreadTicksNowFunction g_thread_ticks_now_function; 69 70 } // namespace internal 71 72 } // namespace base 73 74 #endif // BASE_TIME_TIME_OVERRIDE_H_ 75