library/cpp/threading/queue/mpmc_unordered_ring.h


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#pragma once 
 
/* 
  It's not a general purpose queue. 
  No order guarantee, but it mostly ordered. 
  Items may stuck in almost empty queue. 
  Use UnsafeScanningPop to pop all stuck items. 
  Almost wait-free for producers and consumers. 
 */ 
 
#include <util/system/atomic.h> 
#include <util/generic/ptr.h> 
 
namespace NThreading { 
    struct TMPMCUnorderedRing { 
    public: 
        static constexpr ui16 MAX_PUSH_TRIES = 4; 
        static constexpr ui16 MAX_POP_TRIES = 4; 
 
        TMPMCUnorderedRing(size_t size); 
 
        bool Push(void* msg, ui16 retryCount = MAX_PUSH_TRIES) noexcept; 
        void StubbornPush(void* msg) { 
            while (!WeakPush(msg)) { 
            } 
        } 
 
        void* Pop() noexcept; 
 
        void* UnsafeScanningPop(ui64* last) noexcept; 
 
    private: 
        bool WeakPush(void* msg) noexcept; 
 
        size_t RingSize; 
        TArrayPtr<void*> RingBuffer; 
        ui64 WritePawl = 0; 
        ui64 WriteFront = 0; 
        ui64 ReadPawl = 0; 
        ui64 ReadFront = 0; 
    }; 
}