mirror of
https://github.com/VCMP-SqMod/SqMod.git
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4a6bfc086c
Switched to POCO library for unified platform/library interface. Deprecated the external module API. It was creating more problems than solving. Removed most built-in libraries in favor of system libraries for easier maintenance. Cleaned and secured code with help from static analyzers.
122 lines
2.3 KiB
C++
122 lines
2.3 KiB
C++
//
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// AtomicFlag.h
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//
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// Library: Foundation
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// Package: Core
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// Module: AtomicFlag
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//
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// Definition of the AtomicFlag class.
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//
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// Copyright (c) 2009, Applied Informatics Software Engineering GmbH.
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// and Contributors.
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//
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// SPDX-License-Identifier: BSL-1.0
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//
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#ifndef Foundation_AtomicFlag_INCLUDED
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#define Foundation_AtomicFlag_INCLUDED
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#include "Poco/Foundation.h"
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#include <atomic>
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namespace Poco {
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class Foundation_API AtomicFlag
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/// This class implements an atomic boolean flag by wrapping
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/// the std::atomic_flag. It is guaranteed to be thread-safe
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/// and lock-free.
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///
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/// Only default-construction is allowed, objects of this
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/// class are not copyable, assignable or movable.
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///
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/// Note that this class is not a replacement for (atomic)
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/// bool type because its value can not be read without also
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/// being set to true. However, after being set (either
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/// explicitly, through the set() call or implicitly, via
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/// operator bool()), it can be reset and reused.
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///
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/// The class is useful in scenarios such as busy-wait or
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/// one-off code blocks, e.g.:
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///
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/// class MyClass
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/// {
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/// public:
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/// void myFunc()
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/// {
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/// if (!_beenHere) doOnce();
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/// doMany();
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/// }
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///
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/// void doOnce() { /* executed once */ }
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///
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/// void doMany() { /* executed multiple times */ }
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///
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/// private:
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/// AtomicFlag _beenHere;
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/// }
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///
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/// MyClass myClass;
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/// int i = 0;
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/// while (++i < 10) myClass.myFunc();
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{
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public:
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AtomicFlag() = default;
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/// Creates AtomicFlag.
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~AtomicFlag() = default;
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/// Destroys AtomicFlag.
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bool set();
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/// Sets the flag to true and returns previously
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/// held value.
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void reset();
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/// Resets the flag to false.
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operator bool ();
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/// Sets the flag to true and returns previously
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/// held value.
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private:
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AtomicFlag(const AtomicFlag&) = delete;
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AtomicFlag& operator = (const AtomicFlag&) = delete;
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AtomicFlag(AtomicFlag&&) = delete;
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AtomicFlag& operator = (AtomicFlag&&) = delete;
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std::atomic_flag _flag = ATOMIC_FLAG_INIT;
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};
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//
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// inlines
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//
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inline bool AtomicFlag::set()
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{
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return _flag.test_and_set(std::memory_order_acquire);
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}
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inline void AtomicFlag::reset()
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{
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_flag.clear(std::memory_order_release);
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}
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inline AtomicFlag::operator bool ()
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{
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return set();
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}
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} // namespace Poco
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#endif // Foundation_AtomicFlag_INCLUDED
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