linux进程间通信（posix信号灯+posix共享内存）实例

/*
*
*       Filename:  producer.c
*
*    Description:  生产者进程
*
*        Version:  1.0
*        Created:  09/30/2011 04:52:23 PM
*       Revision:  none
*       Compiler:  gcc(g++)
*
*         Author:  |Zhenghe Zhang|, |zhenghe.zhang@gmail.com|
*        Company:  |Shenzhen XXX Technology Co., Ltd.|
*
*/

#include <stdio.h>
#include <string.h>
#include <stdlib.h>
#include <fcntl.h>
#include <unistd.h>
#include <sys/stat.h>
#include <sys/types.h>
#include <sys/shm.h>
#include <sys/mman.h>
#include <semaphore.h>

#define MAXSHM      5  //定义缓冲区数组的下标变量个数

int main()
{
/*共享文件*/
const char *file = "/shmipcxy";
int fd = shm_open(file, O_CREAT | O_RDWR | O_TRUNC, 0666);
if(fd == -1)
{
perror("shm_open");
exit(1);
}

/*ftruncate()会将参数fd指定的文件大小改为参数length指定的大小。*/
/*参数fd为已打开的文件描述词，而且必须是以写入模式打开的文件。*/
/*如果原来的文件大小比参数length大，则超过的部分会被删去。*/
if(ftruncate(fd, sizeof(char) * MAXSHM) == -1)
{
perror("ftruncate");
exit(1);
}

/*mmap()用来将某个文件内容映射到内存中，对该内存区域的存取即是直接对该文件内容的读写。*/
/*参数start指向欲对应的内存起始地址，通常设为NULL，代表让系统自动选定地址，对应成功后该地址会返回。*/
/*参数length代表将文件中多大的部分对应到内存。*/
char *addr_c = (char*)mmap(NULL, sizeof(char) * MAXSHM,
PROT_READ | PROT_WRITE, MAP_SHARED, fd, 0);
if(*((int*)addr_c) == -1)
{
perror("mmap");
exit(1);
}

const char *full_name = "/tmp_full";
const char *empty_name = "/tmp_empty";
const char *mutex_name = "/tmp_mutex";

/*定义信号灯 full, empty, mutex  */
sem_t *full = sem_open(full_name, O_CREAT, 0600, 0);
sem_t *empty = sem_open(empty_name, O_CREAT, 0600, MAXSHM);
sem_t *mutex = sem_open(mutex_name, O_CREAT, 0600, 1);

int i = 0;

while(i < 10)
{
/*sem_wait锁定一个信号量 */
sem_wait(empty);         //对 empty执行-操作
sem_wait(mutex);         //对 mutex执行-操作

addr_c[i] = i + 'a';
printf("***addr_c[%d] = %c\n", i, addr_c[i]);

/*sem_post解锁一个信号量 */
sem_post(mutex);         //对 mutex执行+操作
sem_post(full);          //对 full执行+操作

i++;
sleep(1);
}

sleep(20); //等待消费者进程退出

/*munmap()用来取消参数start所指的映射内存起始地址，参数length则是欲取消的内存大小。*/
/*当进程结束或利用exec相关函数来执行其他程序时，映射内存会自动解除，但关闭对应的文件描述词时不会解除映射。*/
if(munmap(addr_c, sizeof(char) * MAXSHM) == -1)
{
perror("munmap");
exit(1);
}

/*解引用 POSIX 共享内存对象*/
if(shm_unlink(file) == -1)
{
perror("shm_unlink");
exit(1);
}

/*删除一个命名信号量*/
if(sem_close(full) == -1)
{
perror("sem_close");
exit(1);
}

if(sem_close(empty) == -1)
{
perror("sem_close");
exit(1);
}

if(sem_close(mutex) == -1)
{
perror("sem_close");
exit(1);
}

/*sem_unlink 删除一个由 name 引用的信号量。*/
/*信号量名字被直接删除。信号量本身在所有打开该信号量的进程都关闭它之后被销毁。*/
if(sem_unlink(full_name) == -1)
{
perror("sem_unlink");
exit(1);
}

if(sem_unlink(empty_name) == -1)
{
perror("sem_unlink");
exit(1);
}

if(sem_unlink(mutex_name) == -1)
{
perror("sem_unlink");
exit(1);
}

return 0;
}

/*
*
*       Filename:  consumer.c
*
*    Description:  消费者进程
*
*        Version:  1.0
*        Created:  09/30/2011 04:52:23 PM
*       Revision:  none
*       Compiler:  gcc(g++)
*
*         Author:  |Zhenghe Zhang|, |zhenghe.zhang@gmail.com|
*        Company:  |Shenzhen XXX Technology Co., Ltd.|
*
*/

#include <stdio.h>
#include <string.h>
#include <stdlib.h>
#include <fcntl.h>
#include <unistd.h>
#include <sys/stat.h>
#include <sys/types.h>
#include <sys/shm.h>
#include <sys/mman.h>
#include <semaphore.h>

#define MAXSHM      5  //定义缓冲区数组的下标变量个数

int main()
{
/*共享文件*/
const char *file = "/shmipcxy";
int fd = shm_open(file, O_CREAT | O_RDWR, 0666);
if(fd == -1)
{
perror("shm_open");
exit(1);
}

if(ftruncate(fd, sizeof(char) * MAXSHM) == -1)
{
perror("ftruncate");
exit(1);
}

char *addr_c = (char*)mmap(NULL, sizeof(char) * MAXSHM, PROT_READ | PROT_WRITE, MAP_SHARED, fd, 0);
if(*((int*)addr_c) == -1)
{
perror("mmap");
exit(1);
}

/* 定义信号灯 full,emptyid, mutexid */
const char *full_name = "/tmp_full";
const char *empty_name = "/tmp_empty";
const char *mutex_name = "/tmp_mutex";

/*定义信号灯 full, empty, mutex  */
sem_t *full = sem_open(full_name, 0);
sem_t *empty = sem_open(empty_name, 0);
sem_t *mutex = sem_open(mutex_name, 0);

int i = 0;

while(i < 10)
{
sem_wait(full);       //对full执行 - 操作
sem_wait(mutex);      //对mutex执行 - 操作

printf("***addr_c[%d] = %c\n", i, addr_c[i]);

sem_post(mutex);      //对mutex执行 + 操作
sem_post(empty);      //对empty执行 + 操作

i++;
sleep(2);
}

if(munmap(addr_c, sizeof(char) * MAXSHM) == -1)
{
perror("munmap");
exit(1);
}

if(sem_close(full) == -1)
{
perror("sem_close");
exit(1);
}

if(sem_close(empty) == -1)
{
perror("sem_close");
exit(1);
}

if(sem_close(mutex) == -1)
{
perror("sem_close");
exit(1);
}

return 0;
}