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45 lines
1.3 KiB
C++
45 lines
1.3 KiB
C++
// Copyright (c) 2011 The Chromium Authors. All rights reserved.
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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_SYNCHRONIZATION_ATOMIC_FLAG_H_
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#define BASE_SYNCHRONIZATION_ATOMIC_FLAG_H_
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#include "base/atomicops.h"
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#include "base/base_export.h"
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#include "base/macros.h"
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#include "base/sequence_checker.h"
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namespace base {
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// A flag that can safely be set from one thread and read from other threads.
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//
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// This class IS NOT intended for synchronization between threads.
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class BASE_EXPORT AtomicFlag {
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public:
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AtomicFlag();
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~AtomicFlag() = default;
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// Set the flag. Must always be called from the same sequence.
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void Set();
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// Returns true iff the flag was set. If this returns true, the current thread
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// is guaranteed to be synchronized with all memory operations on the sequence
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// which invoked Set() up until at least the first call to Set() on it.
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bool IsSet() const;
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// Resets the flag. Be careful when using this: callers might not expect
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// IsSet() to return false after returning true once.
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void UnsafeResetForTesting();
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private:
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base::subtle::Atomic32 flag_ = 0;
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SequenceChecker set_sequence_checker_;
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DISALLOW_COPY_AND_ASSIGN(AtomicFlag);
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};
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} // namespace base
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#endif // BASE_SYNCHRONIZATION_ATOMIC_FLAG_H_
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