实验10-共享内存实验

实验10共享内存实验1．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。2．实验内容该实现要求利用共享内存实现文件的翻开和读写操作。3．实验步骤〔1〕画出流程图该实验流程图如下图：流程图〔2〕编写代码下面是共享内存缓冲区的数据结构的定义/*shm_com.h*/#include<unistd.h>#include<stdlib.h>#include<stdio.h>#include<string.h>#include<sys/types.h>#include<sys/ipc.h>#include<sys/shm.h>#defineSHM_BUFF_SZ2048structshm_buff{intpid;charbuffer[SHM_BUFF_SZ];};以下是信号量数据结构定义及其操作代码/*sem_com.h*/#include<sys/types.h>#include<sys/ipc.h>#include<sys/sem.h>unionsemun{intval;structsemid_ds*buf;unsignedshort*array;};/*1.信号量初始化〔赋值〕函数*/intinit_sem(intsem_id,intinit_value)/*用init_value值作初值来初始化标识为sem_id的信号量〕*/{unionsemunsem_union;sem_union.val=init_value;/*init_value为初始值*/if(semctl(sem_id,0,SETVAL,sem_union)==-1){perror("Initializesemaphoreerror!");return-1;}return0;}/*2.从系统中删除信号量的函数*/intdel_sem(intsem_id){unionsemunsem_union;if(semctl(sem_id,0,IPC_RMID,sem_union)==-1){perror("Deletesemaphoreerror");return-1;}return0;}/*3.P操作函数*/intsem_p(intsem_id){structsembufsem_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操作*/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("Poperationerror");return-1;}return0;}/*4.V操作函数*/intsem_v(intsem_id){structsembufsem_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操作*/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("Voperationerror");return-1;}return0;}以下是“生产者〞局部代码/*producer.c*/#include"shm_com.h"#include"sem_com.h"#include<signal.h>intignore_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);return0;}intmain(){void*shared_memory=NULL;structshared_use_st*shm_buff_inst;charbuffer[BUFSIZ];intshmid,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);/*创立一个信号量*/if(semid==-1){perror("semgeterror!");exit(1);}if(init_sem(semid,1)==-1)/*初始值为1*/{perror("sem_initerror!");del_sem(semid);exit(1);}/*创立共享内存*/shmid=shmget(ftok(".",'b'),sizeof(structshared_use_st),0666|IPC_CREAT);if(shmid==-1){perror("shmgetfailed");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("shmaterror");del_sem(semid);exit(1);}printf("Memoryattachedat%X\n",(int)shared_memory);/*获得共享内存的映射地址*/shm_buff_inst=(structshared_use_st*)shared_memory;do{sem_p(semid);printf("Entersometexttothesharedmemory(enter'quit'toexit):");/*向共享内存写入数据*/if(fgets(shm_buff_inst->buffer,SHM_BUFF_SZ,stdin)==NULL){perror("fgetserror");sem_v(semid);break;}shm_buff_inst->pid=getpid();sem_v(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("shmdterror");exit(1);}exit(0);}以下是“消费者〞局部代码/*customer.c*/#include"shm_com.h"#include"sem_com.h"intmain(){void*shared_memory=NULL;structshared_use_st*shm_buff_inst;intshmid,semid;/*获得信号量*/semid=semget(ftok(".",'a'),1,0666);if(semid==-1){perror("Produceris'ntexist");exit(1);}/*获得共享内存*/shmid=shmget(ftok(".",'b'),sizeof(structshared_use_st),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(shared_memory==(void*)-1){perror("shmat");exit(1);}printf("Memoryattachedat%X\n",(int)shared_memory);/*获得共享内存的映射地址*/shm_buff_inst=(structshared_use_st*)shared_memory;do{sem_p(semid);printf("Sharedmemorywaswrittenbyprocess%d:%s",shm_buff_inst->pid,shm_buff_inst->buffer);if(strncmp(shm_buff_inst->buffer,"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){