wait_strategy.hpp

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

#include <thread>

#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 index ) =0;
        virtual void SignalAllWhenBlocking() = 0; //blocking strategy only

    protected:
        StatusOnSharedMem* status_on_shared_mem_;
};

///////////////////////////////////////////////////////////////////////////////
class YieldingWaitStrategy:public WaitStrategyInterface
{
    public:
        
        YieldingWaitStrategy( StatusOnSharedMem* status_on_shared_mem) 
        {
            status_on_shared_mem_= status_on_shared_mem ;
        };
        ~YieldingWaitStrategy() { };

        int64_t Wait(int64_t index) {
            int nCounter = 100;

            while (true) {
                int64_t current_cursor = status_on_shared_mem_->cursor.load() ;

                if( index > current_cursor ) {
                    //spins --> yield
                    if(nCounter ==0) {
                        std::this_thread::yield();
                    } else {
                        nCounter--;
                    }
                    continue;
                } else {
                    return current_cursor;
                }
            }//while
        }

        void SignalAllWhenBlocking()  //blocking strategy only
        {
        }
};

///////////////////////////////////////////////////////////////////////////////
class SleepingWaitStrategy:public WaitStrategyInterface
{
    public:
        
        SleepingWaitStrategy( StatusOnSharedMem* status_on_shared_mem) 
        {
            status_on_shared_mem_= status_on_shared_mem ;
        };
        ~SleepingWaitStrategy() { };

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

            while (true) {
                int64_t current_cursor = status_on_shared_mem_->cursor.load() ;

                if( index > current_cursor ) {
                    //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 current_cursor;
                }
            }//while
        }

        void SignalAllWhenBlocking()  //blocking strategy only
        {
        }
};


///////////////////////////////////////////////////////////////////////////////
#include <sys/time.h>
class BlockingWaitStrategy:public WaitStrategyInterface
{
    public:
        BlockingWaitStrategy( StatusOnSharedMem* status_on_shared_mem) 
        {
            status_on_shared_mem_= status_on_shared_mem ;
        };

        ~BlockingWaitStrategy() { };

        int64_t Wait(int64_t index) {
            while (true) {
                int64_t current_cursor = status_on_shared_mem_->cursor.load() ;

                if( index > current_cursor ) {
                    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 += 1000;

                    pthread_mutex_lock(&(status_on_shared_mem_->mutex_lock) );

                    pthread_cond_timedwait(& (status_on_shared_mem_->cond_var), 
                                           &(status_on_shared_mem_->mutex_lock),
                                           & timeToWait );

                    pthread_mutex_unlock(&(status_on_shared_mem_->mutex_lock));
                } else {
                    return current_cursor;
                }
            }//while
        }

        void SignalAllWhenBlocking()  //blocking strategy only
        {
            //생산자가 Commit 시 호출됨.
            pthread_mutex_lock(&(status_on_shared_mem_->mutex_lock));
            pthread_cond_broadcast(&(status_on_shared_mem_->cond_var));
            pthread_mutex_unlock(&(status_on_shared_mem_->mutex_lock));
        }

    private:
};


#endif