进程锁实现-有名信号量

来源：互联网发布：哈希姆家族知乎编辑：程序博客网时间：2024/06/15 09:35

说明：Linux平台

代码：

/** @file processlock.h*   @brief 进程锁实现*   @date  2015-4-15*   @note 用有名信号量实现*/#pragma once#include <semaphore.h>using std::string;class CProcessLock{public:    CProcessLock();    ~CProcessLock();    bool init(const char *pName);    bool init(const string &name);    void unInit();    void lock();    void unlock();    bool is_good();//锁是否已经创建完成private:    sem_t *sem_;//信号量id    char sem_name[64];//信号量名字    bool init_;//信号量初始化是否完成};

#include <unistd.h>#include <sys/sem.h>#include <fcntl.h>#include <errno.h>#include <string.h>#include <cstdio>#include <cstdlib>#include <string>#include "processlock.h"using std::string;#define OPEN_FLAG O_RDWR|O_CREAT#define OPEN_MODE 00777#define INIT_V 1CProcessLock::CProcessLock(){    init_ = false;    memset(sem_name, 0, 64);}CProcessLock::~CProcessLock(){    unInit();}bool CProcessLock::init(const char *pName){    if(NULL == pName)        return false;    int nLen = strlen(pName);    if(nLen > 64)    {        nLen = 64;    }    memcpy(sem_name, pName, nLen);    sem_ = sem_open(sem_name, OPEN_FLAG, OPEN_MODE, INIT_V);    if(sem_ == SEM_FAILED)    {        printf("create error:%d\n", errno);        return false;    }    else    {        init_ = true;    }    return true;}bool CProcessLock::init(const string &name){    if(name.empty())        return false;    int nLen = name.length();    if(nLen > 64)    {        nLen = 64;    }    memcpy(sem_name, name.c_str(), nLen);    sem_ = sem_open(name.c_str(), OPEN_FLAG, OPEN_MODE, INIT_V);    if(sem_ == SEM_FAILED)    {        printf("create error:%d\n", errno);        return false;    }    else    {        init_ = true;    }    return true;}bool CProcessLock::is_good(){    return init_;}void CProcessLock::unInit(){    if(init_ && sem_!= NULL)    {        sem_unlink(sem_name);//删除系统中的信号量        sem_close(sem_);//销毁打开的信号量    }    init_ = false;    sem_ = NULL;    memset(sem_name, 0, 64);}void CProcessLock::lock(){    sem_wait(sem_);}void CProcessLock::unlock(){    sem_post(sem_);}

//测试用例

/**进程锁测试用例编译：加锁：g++ -Wall -g -DUSE_LOCK -lrt -o test_processlock test_processlock.cpp processlock.cpp不加锁：g++ -Wall -g -lrt -o test_processlock test_processlock.cpp processlock.cpp*/#include <cstdio>#include <iostream>#include <sys/types.h>#include <sys/wait.h>#include "processlock.h"using namespace std;CProcessLock mylock;#define MAX_LEN 1000void print_log(const char *buf){#ifdef USE_LOCK    mylock.lock();#endif    for(int i=0; i<MAX_LEN; i++)    {        printf("%c ", buf[i]);        fflush(stdout);        usleep(2000);    }#ifdef USE_LOCK        mylock.unlock();#endif}int main(int argc, char *argv[]){#ifdef USE_LOCK        mylock.init("mylock");        if(!mylock.is_good())        return 0;#endif    pid_t pid = -1;    int status = -1;    pid = fork();    if(pid == 0)    {        //child process        char buf[MAX_LEN];        int i=0;        for(i=0; i<MAX_LEN-1; i++)        {            buf[i] = 'x';        }        buf[i] = 0;        print_log(buf);        printf("\n");        return 0;    }        //parent process    char buf[MAX_LEN];    int i=0;    for(i=0; i<MAX_LEN-1; i++)    {        buf[i] = 'y';    }    buf[i] = 0;    print_log(buf);    printf("\n");    wait(&status);#ifdef USE_LOCK    mylock.unInit();#endif    return 0;}

运行结果：不加锁时，子进程和父进程的字符交替出现，加锁后能够互斥输出。

参考：

http://blog.chinaunix.net/uid-20940095-id-66101.html

http://blog.csdn.net/ljianhui/article/details/10243617

http://www.oschina.net/code/snippet_237505_8646

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