nlqueue.h

/*
 * lock free queue
 * @author zhouxj
 * @version 1.0, 2018-11-01
 */
#pragma once
#include <atomic>
#include <cstdint>
using namespace std;

//structure to hold a pair of head/tail values and other metadata
struct HeadTail {
        HeadTail() : head(0), tail(0), single(true) {}
        volatile atomic<uint32_t> head;  //prod/consumer head
        volatile atomic<uint32_t> tail;  //prod/consumer tail
        bool single;                     //true if single prod/cons
};

#define RING_SP 0x0001
#define RING_SC 0x0002
#define RING_MP 0x0004
#define RING_MC 0x0008

class NoLockRing {
public:
        NoLockRing(uint32_t size, uint32_t flag);

        ~NoLockRing();

        int init();

        int push(uint32_t size, void *buf);

        int push(void *buf);

        int pop(uint32_t size, void **buf);

        int pop(void **buf);

        uint32_t size();
private:
        //aligns input parameter to the next power of 2
        uint32_t align32pow2(uint32_t size);
        
        //update the prod head for enqueue
        uint32_t updateProdHead(uint32_t size, uint32_t &oldHead, uint32_t &newHead);
        
        //update the cons head for dequeue
        uint32_t updateConsHead(uint32_t size, uint32_t &oldHead, uint32_t &newHead);
        
        //prod enqueue functions, the enqueue of pointers on the ring
        void updateProdData(void **data, uint32_t head, uint32_t size);
        
        //cons dequeue functions, the actuual copy of pointers on the ring to data
        void updateConsData(void **data, uint32_t head, uint32_t size);
        
        //update the prod tail for enqueue
        void updateProdTail(uint32_t oldHead, uint32_t newHead);
        
        //update the cons tail for dequeue
        void updateConsTail(uint32_t oldHead, uint32_t newHead);
        
        //copy pointers functions
        void savePtr(void *dst, void **src, uint32_t dstIndex, uint32_t srcIndex);

        void savePtr(void **dst, void *src, uint32_t dstIndex, uint32_t srcIndex);
private:
        uint32_t    m_size; //the size of ring
        uint32_t    m_mask; //the mask of ring
        uint32_t    m_flag; //single or multi prod/cons
        HeadTail    m_prod; //prod head/tail values
        HeadTail    m_cons; //cons head/tail values
        void*       m_buf;  //pointers buffer
};