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103 lines
2.9 KiB
C++
103 lines
2.9 KiB
C++
//------------------------------------------------------------------------------
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/*
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This file is part of Beast: https://github.com/vinniefalco/Beast
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Copyright 2013, Vinnie Falco <vinnie.falco@gmail.com>
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Permission to use, copy, modify, and/or distribute this software for any
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purpose with or without fee is hereby granted, provided that the above
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copyright notice and this permission notice appear in all copies.
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THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
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WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
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MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
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ANY SPECIAL , DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
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WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
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ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
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OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
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*/
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//==============================================================================
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#ifndef BEAST_ATOMICFLAG_H_INCLUDED
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#define BEAST_ATOMICFLAG_H_INCLUDED
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/*============================================================================*/
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/**
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A thread safe flag.
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This provides a simplified interface to an atomic integer suitable for
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representing a flag. The flag is signaled when on, else it is considered
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reset.
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@ingroup beast_core
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*/
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class BEAST_API AtomicFlag
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{
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public:
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/** Create an AtomicFlag in the reset state. */
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AtomicFlag () noexcept
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:
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m_value (0)
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{
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}
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/** Signal the flag.
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If two or more threads simultaneously attempt to signal the flag,
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only one will receive a true return value.
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@return true if the flag was previously reset.
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*/
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inline bool trySignal () noexcept
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{
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return m_value.compareAndSetBool (1, 0);
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}
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/** Signal the flag.
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The flag must be in the reset state. Only one thread may
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call this at a time.
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*/
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inline void signal () noexcept
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{
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#if BEAST_DEBUG
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const bool success = m_value.compareAndSetBool (1, 0);
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bassert (success);
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#else
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m_value.set (1);
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#endif
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}
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/** Reset the flag.
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The flag must be in the signaled state. Only one thread may
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call this at a time. Usually it is the thread that was successful
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in a previous call to trySignal().
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*/
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inline void reset () noexcept
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{
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#if BEAST_DEBUG
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const bool success = m_value.compareAndSetBool (0, 1);
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bassert (success);
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#else
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m_value.set (0);
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#endif
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}
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/** Check if the AtomicFlag is signaled
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The signaled status may change immediately after this call
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returns. The caller must synchronize.
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@return true if the flag was signaled.
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*/
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inline bool isSignaled () const noexcept
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{
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return m_value.get () == 1;
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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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