試驗10共享內存試驗

1、南昌大學實驗報告學生姓名：王維學號:6100212202專業(yè)班級:網工 121班實驗類型：口 驗證 口綜合口設計口 創(chuàng)新 實驗日期：6/11實驗成績:一、 實驗項目名稱實驗10：共享內存實驗二、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)。三、實驗內容該實現(xiàn)要求利用共享內存實現(xiàn)文件的打開和讀寫操作。四、實驗步驟(1)畫出流程圖 該實驗流程圖如圖所示:流程圖(2)編寫代碼下面是共享內存緩

2、沖區(qū)的數(shù)據(jù)結構的定義/* shm_com.h */#include #include #include #include #include #include #include #define SHM_BUFF_SZ 2048struct shm_buffint pid;char bufferSHM_BUFF_SZ;以下是信號量數(shù)據(jù)結構定義及其操作代碼/* sem_com.h */#include #include #include union semunint val;struct semid_ds *buf;unsigned short *array;/*1.信號量初始化(賦值)函數(shù) */i

3、nt init_sem(int sem_id, int init_value) /* 用 init_value 值作初值來初始化標識為 sem_id 的信號量)*/ union semun sem_union;sem_union.val = init_value; /* init_value 為初始值 */ if (semctl(sem_id, 0, SETVAL, sem_union) = -1) perror(Initialize semaphore error!);return -1;return 0;/* 2. 從系統(tǒng)中刪除信號量的函數(shù) */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 操作函數(shù)*/int sem_p(int sem_id) (struct sembuf sem_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 操彳乍 */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

5、(semop(sem_id, &sem_b, 1) = -1) (perror(P operation error);return -1;return 0;/* 4. V 操作函數(shù)*/int sem_v(int sem_id) (struct sembuf sem_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 操彳乍 */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(V oper

6、ation error);return -1; return 0;以下是“生產者”部分代碼/* producer.c */#include shm_com.h#include sem_com.h#include int ignore_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);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)建一個信號量 */if(semid=-1) perror(semget error!);exit(1);if(init_sem(semid,1) = -1)/* 初始值為 1*/ perror(sem_init error!);del_sem(semid);exit(1);/*創(chuàng)建共享內存 */shmid = shmge

8、t(ftok(., b), sizeof(struct shm_buff), 0666|IPC_CREAT) ;if (shmid = -1)perror(shmget failed);del_sem(semid);exit(1);/*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 error);del_sem(semid);exit(1);printf(Memory attached at %Xn, (int)shared_mem

9、ory);/*獲得共享內存的映射地址*/shm_buff_inst = (struct shm_buff *) shared_memory;do(sem_p(semid);printf(Enter some text to the shared memory(enter quit to exit):);/*向共享內存寫入數(shù)據(jù)*/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);/*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(shmdt error);exit(1);exit(0);以下是“消費者”部分代碼/* 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;/*獲得信號量*/semid = semget(ftok(., a),1,0666);if (semid = -1)(perror(Producer isnt exist);exit(1);/*獲得共享內存*/shmid = shmget(ftok(., b), sizeof(struct shm_buff), 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

12、 (shared_memory = (void*)-1)(perror(shmat);exit(1);printf(Memory attached at %Xn,(int)shared_memory);/*獲得共享內存的映射地址*/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);/*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) perror(shmctl(IPC_RMID);exit(1);exit(0);.編譯produ

14、cer.c和customer.c并運行，記錄結果，完成實驗報告.若將消費者部分中的代碼“sleep(2);”這行刪除，重新編譯運行，會出什么情況？解釋你看到的實驗結果。五、實驗結果打開兩個終端，終端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終端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、實驗總結共享內存是System V的三種IPC類型之一。共享內存是最快的一種IPC方