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114 lines
3.3 KiB
C++
114 lines
3.3 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_UTILITY_STATICOBJECT_H_INCLUDED
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#define BEAST_UTILITY_STATICOBJECT_H_INCLUDED
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namespace beast {
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// Spec: N2914=09-0104
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//
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// [3.6.2] Initialization of non-local objects
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//
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// Objects with static storage duration (3.7.1) or thread storage
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// duration (3.7.2) shall be zero-initialized (8.5) before any
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// other initialization takes place.
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//
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namespace detail {
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extern void staticObjectWait (std::size_t n);
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}
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/** Wrapper to produce an object with static storage duration.
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The object is constructed in a thread-safe fashion when the get function
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is first called. Note that the destructor for Object is never called. To
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invoke the destructor, use the AtExitHook facility (with caution).
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The Tag parameter allows multiple instances of the same Object type, by
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using different tags.
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Object must meet these requirements:
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DefaultConstructible
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@see AtExitHook
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*/
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template <class Object, typename Tag = void>
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class StaticObject
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{
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public:
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static Object& get ()
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{
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StaticData& staticData (StaticData::get());
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if (staticData.state.get() != initialized)
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{
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if (staticData.state.compareAndSetBool (initializing, uninitialized))
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{
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// Initialize the object.
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new (&staticData.object) Object;
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staticData.state = initialized;
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}
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else
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{
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for (std::size_t n = 0; staticData.state.get() != initialized; ++n)
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{
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detail::staticObjectWait (n);
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}
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}
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}
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return staticData.object;
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}
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private:
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enum
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{
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uninitialized = 0, // must be zero to function properly
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initializing,
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initialized
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};
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// This structure gets zero-filled at static initialization time.
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// No constructors are called.
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//
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class StaticData : public Uncopyable
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{
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public:
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Atomic <int> state;
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Object object;
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static StaticData& get ()
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{
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static uint8 storage [sizeof (StaticData)];
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return *(reinterpret_cast <StaticData*> (&storage [0]));
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}
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private:
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StaticData();
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~StaticData();
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};
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};
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}
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#endif
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