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115 lines
3.6 KiB
C++
115 lines
3.6 KiB
C++
/*============================================================================*/
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/*
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VFLib: https://github.com/vinniefalco/VFLib
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Copyright (C) 2008 by Vinnie Falco <vinnie.falco@gmail.com>
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This library contains portions of other open source products covered by
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separate licenses. Please see the corresponding source files for specific
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terms.
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VFLib is provided under the terms of The MIT License (MIT):
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Permission is hereby granted, free of charge, to any person obtaining a copy
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of this software and associated documentation files (the "Software"), to deal
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in the Software without restriction, including without limitation the rights
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to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
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copies of the Software, and to permit persons to whom the Software is
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furnished to do so, subject to the following conditions:
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The above copyright notice and this permission notice shall be included in
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all copies or substantial portions of the Software.
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THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
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IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
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FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
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AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
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LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
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FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS
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IN THE SOFTWARE.
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*/
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/*============================================================================*/
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#ifndef BEAST_ATOMICSTATE_BEASTHEADER
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#define BEAST_ATOMICSTATE_BEASTHEADER
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/*============================================================================*/
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/**
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A thread safe state variable.
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This provides a simplified interface to an integer used to control atomic
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state transitions. A state is distinguished by a single integer value.
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@ingroup beast_core
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*/
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class AtomicState
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{
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public:
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/** Create a new state with an optional starting value.
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@param initialState The initial state.
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*/
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explicit AtomicState (const int initialState = 0) noexcept
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:
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m_value (initialState)
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{
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}
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/** Retrieve the current state.
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This converts the object to an integer reflecting the current state.
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Note that other threads may change the value immediately after this
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function returns. The caller is responsible for synchronizing.
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@return The state at the time of the call.
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*/
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inline operator int () const
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{
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return m_value.get ();
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}
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/** Attempt a state transition.
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The current state is compared to `from`, and if the comparison is
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successful the state becomes `to`. The entire operation is atomic.
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@param from The current state, for comparison.
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@param to The desired new state.
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@return true if the state transition succeeded.
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*/
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inline bool tryChangeState (const int from, const int to) noexcept
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{
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return m_value.compareAndSetBool (to, from);
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}
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/** Perform a state transition.
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This attempts to change the state and generates a diagnostic on
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failure. This routine can be used instead of tryChangeState()
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when program logic requires that the state change must succeed.
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@param from The required current state.
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@param to The new state.
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*/
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inline void changeState (const int from, const int to) noexcept
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{
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#if BEAST_DEBUG
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const bool success = tryChangeState (from, to);
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bassert (success);
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#else
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tryChangeState (from, to);
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#endif
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}
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private:
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Atomic <int> m_value;
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};
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#endif
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