试验10共享内存试验

1、南昌大学实验报告学生姓名：王维学号:6100212202专业班级:网工 121班实验类型：口 验证 口综合口设计口 创新 实验日期：6/11实验成绩:一、 实验项目名称实验10：共享内存实验二、实验目的通过编写共享内存实验， 可以进一步了解使用共享内存的具体步骤，同时也进一步加深对共享内存的理解。在本实验中，采用信号量作为同步机制完善两个进程(“生产者”和“消费者”)之间的通信。其功能类似于“消息队列”中的实例。在实例中使用的与信号量相关 的函数。三、实验内容该实现要求利用共享内存实现文件的打开和读写操作。四、实验步骤(1)画出流程图 该实验流程图如图所示:流程图(2)编写代码下面是共享内存缓

2、冲区的数据结构的定义/* shm_com.h */#include #include #include #include #include #include #include #define SHM_BUFF_SZ 2048struct shm_buffint pid;char bufferSHM_BUFF_SZ;以下是信号量数据结构定义及其操作代码/* sem_com.h */#include #include #include union semunint val;struct semid_ds *buf;unsigned short *array;/*1.信号量初始化(赋值)函数 */i

3、nt init_sem(int sem_id, int init_value) /* 用 init_value 值作初值来初始化标识为 sem_id 的信号量)*/ union semun sem_union;sem_union.val = init_value; /* init_value 为初始值 */ if (semctl(sem_id, 0, SETVAL, sem_union) = -1) perror(Initialize semaphore error!);return -1;return 0;/* 2. 从系统中删除信号量的函数 */int del_sem(int sem_id

4、)union semun sem_union; if (semctl(sem_id, 0, IPC_RMID, sem_union) = -1) (perror(Delete semaphore error);return -1;return 0;/*3. P 操作函数*/int sem_p(int sem_id) (struct sembuf sem_b;sem_b.sem_num = 0; /*单个信号量的编号应该为0 */sem_b.sem_op = -1; /* 表示 P 操彳乍 */sem_b.sem_flg = SEM_UNDO; /*系统自动释放将会在系统中残留的信号量*/if

5、(semop(sem_id, &sem_b, 1) = -1) (perror(P operation error);return -1;return 0;/* 4. V 操作函数*/int sem_v(int sem_id) (struct sembuf sem_b;sem_b.sem_num = 0; /*单个信号量的编号应该为0 */sem_b.sem_op = 1; /* 表示 V 操彳乍 */sem_b.sem_flg = SEM_UNDO; /*系统自动释放将会在系统中残留的信号量*/if (semop(sem_id, &sem_b, 1) = -1) (perror(V oper

6、ation error);return -1; return 0;以下是“生产者”部分代码/* producer.c */#include shm_com.h#include sem_com.h#include int ignore_signal(void)*/*忽略一些信号，免得非法退出程序signal(SIGINT, SIG_IGN);signal(SIGSTOP, SIG_IGN);signal(SIGQUIT, SIG_IGN);return 0;int main() void *shared_memory = NULL;struct shm_buff *shm_buff_inst;c

7、har bufferBUFSIZ;int shmid, semid;ignore_signal(); /*防止程序非正常退出 */*定义信号量，用于实现访问共享内存的进程之间的互斥*/semid = semget(ftok(.,a),1,0666|IPC_CREAT);/* 创建一个信号量 */if(semid=-1) perror(semget error!);exit(1);if(init_sem(semid,1) = -1)/* 初始值为 1*/ perror(sem_init error!);del_sem(semid);exit(1);/*创建共享内存 */shmid = shmge

8、t(ftok(., b), sizeof(struct shm_buff), 0666|IPC_CREAT) ;if (shmid = -1)perror(shmget failed);del_sem(semid);exit(1);/*将共享内存地址映射到当前进程地址空间*/shared_memory = shmat(shmid, (void*)0, 0);if (shared_memory = (void*)-1)(perror(shmat error);del_sem(semid);exit(1);printf(Memory attached at %Xn, (int)shared_mem

9、ory);/*获得共享内存的映射地址*/shm_buff_inst = (struct shm_buff *) shared_memory;do(sem_p(semid);printf(Enter some text to the shared memory(enter quit to exit):);/*向共享内存写入数据*/if (fgets(shm_buff_inst-buffer, SHM_BUFF_SZ, stdin) = NULL) (perror(fgets error);sem_v(semid);break;shm_buff_inst-pid = getpid();sem_v(

10、semid); while(strncmp(shm_buff_inst-buffer, quit, 4) != 0);/*删除信号量*/del_sem(semid);/*删除共享内存到当前进程地址空间中的映射*/if (shmdt(shared_memory) = 1)(perror(shmdt error);exit(1);exit(0);以下是“消费者”部分代码/* customer.c */#include shm_com.h#include sem_com.hint main() void *shared_memory = NULL;struct shm_buff *shm_buff_

11、inst;int shmid, semid;/*获得信号量*/semid = semget(ftok(., a),1,0666);if (semid = -1)(perror(Producer isnt exist);exit(1);/*获得共享内存*/shmid = shmget(ftok(., b), sizeof(struct shm_buff), 0666|IPC_CREAT);if (shmid = -1)(perror(shmget);exit(1);/*将共享内存地址映射到当前进程地址空间*/shared_memory = shmat(shmid, (void*)0, 0);if

12、 (shared_memory = (void*)-1)(perror(shmat);exit(1);printf(Memory attached at %Xn,(int)shared_memory);/*获得共享内存的映射地址*/shm_buff_inst = (struct shm_buff *)shared_memory;do(sem_p(semid);printf(Shared memory was written by process %d :%s,shm_buff_inst-pid, shm_buff_inst-buffer);if (strncmp(shm_buff_inst-b

13、uffer, quit, 4) = 0)(break;shm_buff_inst-pid = 0;memset(shm_buff_inst-buffer, 0, SHM_BUFF_SZ);sem_v(semid);sleep(2); while(1);/*删除共享内存到当前进程地址空间中的映射*/if (shmdt(shared_memory) = -1) perror(shmdt);exit(1);/*删除共享内存*/if (shmctl(shmid, IPC_RMID, NULL) = -1) perror(shmctl(IPC_RMID);exit(1);exit(0);.编译produ

14、cer.c和customer.c并运行，记录结果，完成实验报告.若将消费者部分中的代码“sleep(2);”这行删除，重新编译运行，会出什么情况？解释你看到的实验结果。五、实验结果打开两个终端，终端1：jsllylocalhost bin5 ./producerMemory attached Enter some text Enter some text Enter some textat to to to797AOOO the shared the shared the sharedjellyGlocalhcst binSmemory(enter memory(enter memory(en

15、terrquit* to exit) :hello rqu.it to exit) :world rqu.it * to exit) : quit终端2:jLlyGloeaLhost bin$ ./eustom&rMemouy attached at 32053000Shared msitiory wa.s writt&n fay process 3132:world:quitShared memory was written by process 3132Shared memory was writt&n hy process 313-2 jellyG locaIhost- bin $六、实验总结共享内存是System V的三种IPC类型之一。共享内存是最快的一种IPC方