92 lines
1.9 KiB
C++
92 lines
1.9 KiB
C++
//| Copyright: (C) 2020-2024 Kevin Larke <contact AT larke DOT org>
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//| License: GNU GPL version 3.0 or above. See the accompanying LICENSE file.
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#ifndef cwSpScQueueTmpl_H
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#define cwSpScQueueTmpl_H
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namespace cw
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{
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template< typename T >
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class spScQueueTmpl
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{
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public:
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spScQueueTmpl( unsigned eleN )
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{
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_aN = eleN;
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_aV = mem::allocZ<T>(eleN);
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_wi.store(0,std::memory_order_release);
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_ri.store(0,std::memory_order_release);
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}
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virtual ~spScQueueTmpl()
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{
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mem::release(_aV);
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}
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T* get()
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{
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unsigned ri = _ri.load( std::memory_order_acquire );
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unsigned wi = _wi.load( std::memory_order_relaxed ); // _wi is written in this thread
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// calc. the count of full elements
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unsigned n = wi >= ri ? wi-ri : (_aN-ri) + wi;
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// there must always be at least one empty element because
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// wi can never be advanced to equal ri.
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if( n >= _aN-1 )
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return nullptr;
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return _aV + wi;
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}
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void publish()
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{
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unsigned wi = _wi.load( std::memory_order_relaxed ); // _wi is written in this thread
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wi = (wi+1) % _aN;
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// advance the write position
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_wi.store( wi, std::memory_order_release );
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}
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T* pop()
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{
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unsigned ri = _ri.load( std::memory_order_relaxed );
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unsigned wi = _wi.load( std::memory_order_acquire );
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unsigned n = wi >= ri ? wi-ri : (_aN-ri) + wi;
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if( n == 0 )
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return nullptr;
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T* v = _aV + ri;
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ri = (ri+1) % _aN;
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_ri.store( ri, std::memory_order_release);
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return v;
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}
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private:
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unsigned _aN = 0;
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T* _aV = nullptr;
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std::atomic<unsigned> _wi;
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std::atomic<unsigned> _ri;
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// Note: // _wi==_ri indicates an empty buffer.
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// _wi may never be advanced such that it equals _ri, however
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// _ri may be advanced such that it equals _wi.
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};
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rc_t testSpScQueueTmpl();
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}
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#endif
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