46 lines
1.4 KiB
C++
46 lines
1.4 KiB
C++
// Copyright 2018 The Chromium Authors
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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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#ifndef BASE_TASK_COMMON_LAZY_NOW_H_
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#define BASE_TASK_COMMON_LAZY_NOW_H_
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#include "base/base_export.h"
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#include "base/memory/raw_ptr_exclusion.h"
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#include "base/time/time.h"
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#include "third_party/abseil-cpp/absl/types/optional.h"
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namespace base {
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class TickClock;
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// Now() is somewhat expensive so it makes sense not to call Now() unless we
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// really need to and to avoid subsequent calls if already called once.
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// LazyNow objects are expected to be short-living to represent accurate time.
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class BASE_EXPORT LazyNow {
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public:
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explicit LazyNow(TimeTicks now);
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explicit LazyNow(absl::optional<TimeTicks> now, const TickClock* tick_clock);
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explicit LazyNow(const TickClock* tick_clock);
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LazyNow(const LazyNow&) = delete;
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LazyNow& operator=(const LazyNow&) = delete;
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LazyNow(LazyNow&& move_from) noexcept;
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// Result will not be updated on any subsesequent calls.
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TimeTicks Now();
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bool has_value() const { return !!now_; }
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private:
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absl::optional<TimeTicks> now_;
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// `tick_clock_` is not a raw_ptr<TickClock> as a performance optimization:
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// The pointee doesn't need UaF protection (it has the same lifetime as the
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// theead/sequence).
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RAW_PTR_EXCLUSION const TickClock* tick_clock_; // Not owned.
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};
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} // namespace base
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#endif // BASE_TASK_COMMON_LAZY_NOW_H_
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