POSIX共享内存实现进程间通信
1、进程a:
1 /* 2 ============================================================================ 3 Name : timer.c 4 Author : liuguanghui 5 Version : 6 Copyright : Your copyright notice 7 Description : Hello World in C, Ansi-style 8 ============================================================================ 9 */ 10 11 #include <stdio.h> 12 #include <fcntl.h> 13 #include <stdlib.h> 14 #include <unistd.h> 15 #include <sys/mman.h> 16 #include <sys/stat.h> 17 #include <sys/types.h> 18 #include <errno.h> 19 #include <semaphore.h> 20 #include <pthread.h> 21 22 //利用select函数完成一个定时器的功能； 23 void setTimer(int seconds, int microseconds) 24 { 25 struct timeval temp; 26 temp.tv_sec = seconds; 27 temp.tv_usec = microseconds; 28 select(0, NULL, NULL, NULL, &temp); 29 return ; 30 } 31 32 struct shm_data 33 { 34 int data_int; 35 double data_double; 36 }; 37 38 int main() 39 { 40 int fd; 41 struct shm_data *ptr; 42 shm_unlink("shm1"); 43 if((fd = shm_open("shm1", O_RDWR | O_CREAT | O_EXCL, (S_IRUSR | S_IWUSR | S_IRGRP | S_IROTH))) == -1) 44 { 45 perror("shm_open error"); 46 exit(-1); 47 } 48 ftruncate(fd,sizeof( struct shm_data)); //格式化； 49 if((ptr = mmap(NULL,sizeof(struct shm_data), PROT_READ | PROT_WRITE,MAP_SHARED,fd,0)) == MAP_FAILED) 50 { 51 perror("mmap error"); 52 exit(-1); 53 } 54 close(fd); 55 56 57 sem_t* a; 58 int er=0; 59 sem_unlink("sem_test"); //若内存中已经存在名为“sem_test”的信号量，则将其删除； 60 // 创建一个名为"sem_test"的信号量，并将其值初始化为1，a为sem_t型指针，指向该信号量； 61 a=sem_open("sem_test", O_CREAT ,(S_IRUSR | S_IWUSR | S_IRGRP | S_IROTH), 1); 62 if(NULL==a) 63 { 64 printf("sem_open failure!\n"); 65 } 66 //将该信号量赋为1，且为进程间共享型信号量； 67 sem_init(a,1,1); 68 69 //获取当前信号量的值； 70 sem_getvalue(a, &er); 71 while(1) 72 { 73 if(er==0) 74 { 75 sem_post(a); 76 } 77 setTimer(1,0); 78 sem_getvalue(a, &er); 79 ptr->data_int++; 80 ptr->data_double = 3.0 * ptr->data_int ; 81 82 } 83 return 0; 84 }
2、进程b:
1 /* 2 ============================================================================ 3 Name : test.c 4 Author : liuguanghui 5 Version : 6 Copyright : Your copyright notice 7 Description : Hello World in C, Ansi-style 8 ============================================================================ 9 */ 10 11 #include <stdio.h> 12 #include <fcntl.h> 13 #include <stdlib.h> 14 #include <unistd.h> 15 #include <sys/mman.h> 16 #include <sys/stat.h> 17 #include <sys/types.h> 18 #include <errno.h> 19 #include <semaphore.h> 20 #include <pthread.h> 21 22 struct shm_data 23 { 24 int data_int; 25 double data_double; 26 }; 27 int main() 28 { 29 int fd; 30 struct shm_data *ptr; 31 32 if((fd = shm_open("shm1", O_RDWR, (S_IRUSR | S_IWUSR | S_IRGRP | S_IROTH))) == -1) 33 { 34 perror("shm_open error"); 35 exit(-1); 36 } 37 if((ptr = mmap(NULL,sizeof(struct shm_data), PROT_READ | PROT_WRITE, MAP_SHARED, fd, 0)) == MAP_FAILED) 38 { 39 perror("mmap error"); 40 exit(-1); 41 } 42 close(fd); 43 44 sem_t* x; 45 //sem_open()函数第2个参数为0，表示打开已存在的名为"sem_test"的信号量； 46 x=sem_open("sem_test" , 0, (S_IRUSR | S_IWUSR | S_IRGRP | S_IROTH), 1); 47 if(NULL==x) 48 { 49 printf("sem_open failure!\n"); 50 } 51 int i=0; 52 53 while(1) 54 { 55 sem_wait(x); //当进程 a 完成sem_post动作时，该进程开始继续执行； 56 printf("i = %d\n",i++); 57 printf("%d, %f\n", ptr->data_int,ptr->data_double); 58 } 59 return 0; 60 }
