Repo created

TMessagesProj/jni/voip/webrtc/base/time/time_override.h

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+// Copyright 2018 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#ifndef BASE_TIME_TIME_OVERRIDE_H_
+#define BASE_TIME_TIME_OVERRIDE_H_
+
+#include "base/base_export.h"
+#include "base/time/time.h"
+
+namespace base {
+
+using TimeNowFunction = decltype(&Time::Now);
+using TimeTicksNowFunction = decltype(&TimeTicks::Now);
+using ThreadTicksNowFunction = decltype(&ThreadTicks::Now);
+
+// Time overrides should be used with extreme caution. Discuss with //base/time
+// OWNERS before adding a new one.
+namespace subtle {
+
+// Override the return value of Time::Now and Time::NowFromSystemTime /
+// TimeTicks::Now / ThreadTicks::Now to emulate time, e.g. for tests or to
+// modify progression of time. Note that the override should be set while
+// single-threaded and before the first call to Now() to avoid threading issues
+// and inconsistencies in returned values. Nested overrides are not allowed.
+class BASE_EXPORT ScopedTimeClockOverrides {
+ public:
+  // Pass |nullptr| for any override if it shouldn't be overriden.
+  ScopedTimeClockOverrides(TimeNowFunction time_override,
+                           TimeTicksNowFunction time_ticks_override,
+                           ThreadTicksNowFunction thread_ticks_override);
+
+  // Restores the platform default Now() functions.
+  ~ScopedTimeClockOverrides();
+
+  static bool overrides_active() { return overrides_active_; }
+
+ private:
+  static bool overrides_active_;
+
+  DISALLOW_COPY_AND_ASSIGN(ScopedTimeClockOverrides);
+};
+
+// These methods return the platform default Time::Now / TimeTicks::Now /
+// ThreadTicks::Now values even while an override is in place. These methods
+// should only be used in places where emulated time should be disregarded. For
+// example, they can be used to implement test timeouts for tests that may
+// override time.
+BASE_EXPORT Time TimeNowIgnoringOverride();
+BASE_EXPORT Time TimeNowFromSystemTimeIgnoringOverride();
+BASE_EXPORT TimeTicks TimeTicksNowIgnoringOverride();
+BASE_EXPORT ThreadTicks ThreadTicksNowIgnoringOverride();
+
+}  // namespace subtle
+
+namespace internal {
+
+// These function pointers are used by platform-independent implementations of
+// the Now() methods and ScopedTimeClockOverrides. They are set to point to the
+// respective NowIgnoringOverride functions by default, but can also be set by
+// platform-specific code to select a default implementation at runtime, thereby
+// avoiding the indirection via the NowIgnoringOverride functions. Note that the
+// pointers can be overridden and later reset to the NowIgnoringOverride
+// functions by ScopedTimeClockOverrides.
+extern TimeNowFunction g_time_now_function;
+extern TimeNowFunction g_time_now_from_system_time_function;
+extern TimeTicksNowFunction g_time_ticks_now_function;
+extern ThreadTicksNowFunction g_thread_ticks_now_function;
+
+}  // namespace internal
+
+}  // namespace base
+
+#endif  // BASE_TIME_TIME_OVERRIDE_H_