tick_clock.h (1531B)
1 // Copyright 2012 The Chromium Authors 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_TICK_CLOCK_H_ 6 #define BASE_TIME_TICK_CLOCK_H_ 7 8 #include "base/base_export.h" 9 #include "base/time/time.h" 10 11 namespace base { 12 13 // A TickClock is an interface for objects that vend TimeTicks. It is 14 // intended to be able to test the behavior of classes with respect to 15 // non-decreasing time. 16 // 17 // Note: Overriding Time/TimeTicks altogether via 18 // TaskEnvironment::TimeSource::MOCK_TIME is now the preferred way of overriding 19 // time in unit tests. As such, there shouldn't be many new use cases for 20 // TickClock/DefaultTickClock anymore. 21 // 22 // See DefaultTickClock (base/time/default_tick_clock.h) for the default 23 // implementation that simply uses TimeTicks::Now(). 24 // 25 // (Other implementations that use TimeTicks::NowFromSystemTime() should 26 // be added as needed.) 27 // 28 // See SimpleTestTickClock (base/test/simple_test_tick_clock.h) for a 29 // simple test implementation. 30 // 31 // See Clock (base/time/clock.h) for the equivalent interface for Times. 32 class BASE_EXPORT TickClock { 33 public: 34 virtual ~TickClock(); 35 36 // NowTicks() must be safe to call from any thread. The caller may 37 // assume that NowTicks() is monotonic (but not strictly monotonic). 38 // In other words, the returned TimeTicks will never decrease with 39 // time, although they might "stand still". 40 virtual TimeTicks NowTicks() const = 0; 41 }; 42 43 } // namespace base 44 45 #endif // BASE_TIME_TICK_CLOCK_H_