Linux同步事件是什么,在Linux上处理共享对象的同步事件(2)

清单 5. 修改 ObjectWithEvents.cpp

// To add a declaration for the "new" operator:

class ObjectWithEvents : public IObjectWithEvents

{

public:void * operator new(unsigned int);

};

// To include an additional header for the Initializer class:

#include "Initializer.h"

// To overload the operator "new":

void * ObjectWithEvents::operator new(unsigned int)

{return ms_pObjectWithEvents;

}

// Then, FireEvent is completely changed:

void ObjectWithEvents::FireEvent()

{// We need to serialize all access to the collection by more than one processint iRetVal = Initializer::LockMutex();

if (0 != iRetVal){return;}

pid_t pid = getpid();

// iterate through the collection and fire only events belonging to the current processfor (long i = 0; i < m_npEI; i++){// Check whether the handler belongs to the current process.if (pid != m_alPID[i]){continue;}

//Recheck for NULLif (0 != m_apEI[i]){m_apEI[i]->OnEvent(pid, "");}}

// release the mutexif ((0 == iRetVal) && (0 != Initializer::UnlockMutex())){// Deal with error.}

return;

}

// The following are changes to ObjectWithEvents::AddEventHandler():

// 1. Before accessing the collection, we lock the mutex:

int bRetVal = Initializer::LockMutex();

if (0 != bRetVal)

{return false;

}

// 2. After accessing the collection, we release the mutex:

if ((0 == bRetVal) && (0 != Initializer::UnlockMutex()))

{// Deal with error.

}要对共享内存中的对象进行实例化，请定义另外一个类 Initializer。

清单 6. Initializer.h

#ifndef __Initializer_H__

#define __Initializer_H__

class Initializer

{

public : int m_shmid; static Initializer ms_Initializer; Initializer();

static pthread_mutex_t ms_mutex; static int LockMutex(); static int UnlockMutex();

};

#endif // __Initializer_H__Initializer 定义了共享内存的 id m_shmid 和一个用来处理同步事件的信号量 ms_mutex。

函数 LockMutex() 负责对这个互斥体进行加锁，UnlockMutex() 对这个互斥体进行解锁。

Initializer 的实现如清单 7 所示：

清单 7. Initializer.cpp

#include #include #include #include #include #include "Initializer.h"

#include "ObjectWithEvents.h"

using namespace std;

Initializer Initializer::ms_Initializer;

pthread_mutex_t Initializer::ms_mutex = PTHREAD_ERRORCHECK_MUTEX_INITIALIZER_NP;

Initializer::Initializer() : m_shmid(-1)

{bool bCreated = false;key_t key = 0x1234;

m_shmid = shmget(key,sizeof(ObjectWithEvents), 0666);

if (-1 == m_shmid){if(ENOENT != errno){cerr<

即使在所有进程都与之脱离之后，这个共享内存也不会被销毁。这样您就可以使用 ipcrm 显式地删除，或者使用 ipcs 命令进行查看。测试程序的编译方式如下：

g++ -g -o shm_client shm_client1.cpp ObjectWithEvents.cpp Initializer.cpp

控制台上运行这个程序的结果如下所示：

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