wait_strategy.hpp

/****************************************************************************
 Copyright (c) 2015, ko jung hyun
 
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#ifndef WAIT_STRATEGY_INTERFACE_HPP
#define WAIT_STRATEGY_INTERFACE_HPP
//20150721 kojh create

#include <thread>
#include <sys/time.h>
#include "common_def.hpp"
#include "ring_buffer_on_shmem.hpp"

typedef enum _ENUM_WAIT_STRATEGY_
{
    BLOCKING_WAIT,
    YIELDING_WAIT,
    SLEEPING_WAIT
} ENUM_WAIT_STRATEGY;

///////////////////////////////////////////////////////////////////////////////
class WaitStrategyInterface
{
    public:
        WaitStrategyInterface() {};
        virtual ~WaitStrategyInterface() {};
        virtual int64_t Wait( int64_t nIndex ) =0;
        virtual void SignalAllWhenBlocking() = 0; //blocking strategy only
    protected:
        RingBufferStatusOnSharedMem* pRingBufferStatusOnSharedMem_;
};

///////////////////////////////////////////////////////////////////////////////
class YieldingWaitStrategy:public WaitStrategyInterface
{
    public:
        YieldingWaitStrategy(RingBufferStatusOnSharedMem* pRingBufferStatusOnSharedMem) 
        {
            pRingBufferStatusOnSharedMem_= pRingBufferStatusOnSharedMem ;
        };
        ~YieldingWaitStrategy() { };

        int64_t Wait(int64_t nIndex) {
            int nCounter = 100;
            while (true) {
                int64_t nCurrentCursor = pRingBufferStatusOnSharedMem_->cursor.load() ;
                if( nIndex > nCurrentCursor ) {
                    //spins --> yield
                    if(nCounter ==0) {
                        std::this_thread::yield();
                    } else {
                        nCounter--;
                    }
                    continue;
                } else {
                    return nCurrentCursor;
                }
            }//while
        }
        void SignalAllWhenBlocking() {  //blocking strategy only
        }
};

///////////////////////////////////////////////////////////////////////////////
class SleepingWaitStrategy:public WaitStrategyInterface
{
    public:
        SleepingWaitStrategy( RingBufferStatusOnSharedMem* pRingBufferStatusOnSharedMem) 
        {
            pRingBufferStatusOnSharedMem_= pRingBufferStatusOnSharedMem ;
        };
        ~SleepingWaitStrategy() { };

        int64_t Wait(int64_t nIndex) {
            int nCounter = 200;

            while (true) {
                int64_t nCurrentCursor = pRingBufferStatusOnSharedMem_->cursor.load() ;
                if( nIndex > nCurrentCursor ) {
                    //spins --> yield --> sleep
                    if(nCounter > 100) {
                        nCounter--;
                    } else if(nCounter > 0) {
                        std::this_thread::yield();
                        nCounter--;
                    } else {
                        std::this_thread::sleep_for(std::chrono::nanoseconds(1)); 
                    }
                    continue;
                } else {
                    return nCurrentCursor;
                }
            }//while
        }
        void SignalAllWhenBlocking() { //blocking strategy only
        }
};

///////////////////////////////////////////////////////////////////////////////
class BlockingWaitStrategy:public WaitStrategyInterface
{
    public:
        BlockingWaitStrategy( RingBufferStatusOnSharedMem* pRingBufferStatusOnSharedMem) 
        {
            pRingBufferStatusOnSharedMem_= pRingBufferStatusOnSharedMem ;
        };
        ~BlockingWaitStrategy() { };

        int64_t Wait(int64_t nIndex) {
            while (true) {
                int64_t nCurrentCursor = pRingBufferStatusOnSharedMem_->cursor.load() ;
                if( nIndex > nCurrentCursor ) {
                    struct timespec timeToWait;
                    struct timeval now;
                    gettimeofday(&now,NULL);
                    timeToWait.tv_sec  = now.tv_sec;
                    timeToWait.tv_nsec = now.tv_usec * 1000;
                    timeToWait.tv_sec += 1;
                    //timeToWait.tv_nsec += 100;
                    pthread_mutex_lock(&(pRingBufferStatusOnSharedMem_->mtx_lock) );

                    pthread_cond_timedwait(& (pRingBufferStatusOnSharedMem_->cond_var), 
                                           &(pRingBufferStatusOnSharedMem_->mtx_lock),
                                           & timeToWait );
                    pthread_mutex_unlock(&(pRingBufferStatusOnSharedMem_->mtx_lock));
                } else {
                    return nCurrentCursor;
                }
            }//while
        }
        void SignalAllWhenBlocking() {  //blocking strategy only
            //생산자가 Commit 시 호출됨.
            pthread_mutex_lock(&(pRingBufferStatusOnSharedMem_->mtx_lock));
            pthread_cond_broadcast(&(pRingBufferStatusOnSharedMem_->cond_var));
            pthread_mutex_unlock(&(pRingBufferStatusOnSharedMem_->mtx_lock));
        }
};

#endif //WAIT_STRATEGY_INTERFACE_HPP