临界区互斥的实现

#ifndef CRITICAL_H_
#define CRITICAL_H_
#include <sys/ipc.h>
#include <sys/sem.h>
typedef int CRITICAL_SEC;
union semun {
int val;
struct semid_ds *buf;
unsigned short int *array;
struct seminfo *__buf; };

class CCriticalSec
{
public:
CCriticalSec()
{
m_pCriticalSec = semget (IPC_PRIVATE, 1, IPC_CREAT); //创建信号量
union semun argument;
unsigned short values[1];
values[0] = 1;
argument.array = values;
semctl (m_pCriticalSec, 0, SETALL, argument);
}
~CCriticalSec()
{
union semun ignored_argument;
semctl (m_pCriticalSec, 1, IPC_RMID, ignored_argument);
}
unsigned short Lock()
{
struct sembuf operations[1];
/* Use the first (and only) semaphore. */
operations[0].sem_num = 0;
/* Decrement by 1. */
operations[0].sem_op = -1;
/* Permit undo ing. */
operations[0].sem_flg = SEM_UNDO;
return semop (m_pCriticalSec, operations, 1);
}

unsigned short Unlock()
{
struct sembuf operations[1];
/* Use the first (and only) semaphore. */
operations[0].sem_num = 0;
/* Increment by 1. */
operations[0].sem_op = 1;
/* Permit undo ing. */
operations[0].sem_flg = SEM_UNDO;
return semop (m_pCriticalSec, operations, 1);
}
private:
CRITICAL_SEC m_pCriticalSec;
};
#endif