實驗10-共享內存實驗

實驗10共享內存實驗1．實驗目的通過編寫共享內存實驗，可以進一步了解使用共享內存的具體步驟，同時也進一步加深對共享內存的理解。在本實驗中，采用信號量作為同步機制完善兩個進程〔“生產者〞和“消費者〞〕之間的通信。其功能類似于“消息隊列〞中的實例。在實例中使用的與信號量相關的函數(shù)。2．實驗內容該實現(xiàn)要求利用共享內存實現(xiàn)文件的翻開和讀寫操作。3．實驗步驟〔1〕畫出流程圖該實驗流程圖如下圖：流程圖〔2〕編寫代碼下面是共享內存緩沖區(qū)的數(shù)據(jù)結構的定義/*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];};以下是信號量數(shù)據(jù)結構定義及其操作代碼/*sem_com.h*/#include<sys/types.h>#include<sys/ipc.h>#include<sys/sem.h>unionsemun{intval;structsemid_ds*buf;unsignedshort*array;};/*1.信號量初始化〔賦值〕函數(shù)*/intinit_sem(intsem_id,intinit_value)/*用init_value值作初值來初始化標識為sem_id的信號量〕*/{unionsemunsem_union;sem_union.val=init_value;/*init_value為初始值*/if(semctl(sem_id,0,SETVAL,sem_union)==-1){perror("Initializesemaphoreerror!");return-1;}return0;}/*2.從系統(tǒng)中刪除信號量的函數(shù)*/intdel_sem(intsem_id){unionsemunsem_union;if(semctl(sem_id,0,IPC_RMID,sem_union)==-1){perror("Deletesemaphoreerror");return-1;}return0;}/*3.P操作函數(shù)*/intsem_p(intsem_id){structsembufsem_b;sem_b.sem_num=0;/*單個信號量的編號應該為0*/sem_b.sem_op=-1;/*表示P操作*/sem_b.sem_flg=SEM_UNDO;/*系統(tǒng)自動釋放將會在系統(tǒng)中殘留的信號量*/if(semop(sem_id,&sem_b,1)==-1){perror("Poperationerror");return-1;}return0;}/*4.V操作函數(shù)*/intsem_v(intsem_id){structsembufsem_b;sem_b.sem_num=0;/*單個信號量的編號應該為0*/sem_b.sem_op=1;/*表示V操作*/sem_b.sem_flg=SEM_UNDO;/*系統(tǒng)自動釋放將會在系統(tǒng)中殘留的信號量*/if(semop(sem_id,&sem_b,1)==-1){perror("Voperationerror");return-1;}return0;}以下是“生產者〞局部代碼/*producer.c*/#include"shm_com.h"#include"sem_com.h"#include<signal.h>intignore_signal(void){/*忽略一些信號，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*//*定義信號量，用于實現(xiàn)訪問共享內存的進程之間的互斥*/semid=semget(ftok(".",'a'),1,0666|IPC_CREAT);/*創(chuàng)立一個信號量*/if(semid==-1){perror("semgeterror!");exit(1);}if(init_sem(semid,1)==-1)/*初始值為1*/{perror("sem_initerror!");del_sem(semid);exit(1);}/*創(chuàng)立共享內存*/shmid=shmget(ftok(".",'b'),sizeof(structshared_use_st),0666|IPC_CREAT);if(shmid==-1){perror("shmgetfailed");del_sem(semid);exit(1);}/*將共享內存地址映射到當前進程地址空間*/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);/*獲得共享內存的映射地址*/shm_buff_inst=(structshared_use_st*)shared_memory;do{sem_p(semid);printf("Entersometexttothesharedmemory(enter'quit'toexit):");/*向共享內存寫入數(shù)據(jù)*/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);/*刪除信號量*/del_sem(semid);/*刪除共享內存到當前進程地址空間中的映射*/if(shmdt(shared_memory)==1){perror("shmdterror");exit(1);}exit(0);}以下是“消費者〞局部代碼/*customer.c*/#include"shm_com.h"#include"sem_com.h"intmain(){void*shared_memory=NULL;structshared_use_st*shm_buff_inst;intshmid,semid;/*獲得信號量*/semid=semget(ftok(".",'a'),1,0666);if(semid==-1){perror("Produceris'ntexist");exit(1);}/*獲得共享內存*/shmid=shmget(ftok(".",'b'),sizeof(structshared_use_st),0666|IPC_CREAT);if(shmid==-1){perror("shmget");exit(1);}/*將共享內存地址映射到當前進程地址空間*/shared_memory=shmat(shmid,(void*)0,0);if(shared_memory==(void*)-1){perror("shmat");exit(1);}printf("Memoryattachedat%X\n",(int)shared_memory);/*獲得共享內存的映射地址*/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);/*刪除共享內存到當前進程地址空間中的映射*/if(shmdt(shared_memory)==-1){perror("shmdt");exit(1);}/*刪除共享內存*/if(shmctl(shmid,IPC_RMID,NULL)==-1){