test_memory_bk.c

linux下的人机对话编程

#include <sys/types.h>
#include <sys/ipc.h>
#include <sys/shm.h>
#include <sys/sem.h>
#include <stdio.h>
#include <unistd.h>
#include<stdlib.h>
main(void)
/*
**   Listing3.5.c - simulataneous handling of deposits and withdrawls
*/
{
   struct area {  /* shared memory area */
      int balance;
      int deposit;
      int withdrawal;
	int flag_pro;
   } area, *ap;
   /* semaphores */
   struct sembuf buf;
#if defined(__GNU_LIBRARY__) && !defined(_SEM_SEMUN_UNDEFINED)
   /* union semun is defined by including <sys/sem.h> */
#else
   /* otherwise, according to X/OPEN we have to define it ourselves */
   union semun
   {
      int val;                    /* value for SETVAL */
      struct semid_ds *buf;       /* buffer for IPC_STAT, IPC_SET */
      unsigned short int *array;  /* array for GETALL, SETALL */
      struct seminfo *__buf;      /* buffer for IPC_INFO */
   };
#endif 
   union semun un;

   int flag = (IPC_CREAT | IPC_EXCL | 0660);
   int size = sizeof(struct area);
   key_t skey = 0x04030201; /* sample keys */
   key_t mkey = 0x01020316;
   int semid; /* semaphore id */
   int shmid; /* shared memory id */
   int pidD;  /* deposit child task pid */
   int pidW;  /* withdrawal child task pid */
	int pidT;
   int amount;
   char inbuf[80];

   /* get a shared memory area */
   shmid = shmget(mkey, size, flag);

   /* attach the shared memory area */
   ap = (struct area *) shmat(shmid, 0, 0);

   /* initialize account info in shared memory */
   ap->balance = 1000; /* initialize balance to $1000 */
   ap->withdrawal = 0;
   ap->deposit = 0;
	ap->flag_pro=1;

   /* get and initialize a semaphore */
   semid = semget(skey, 1, flag);
   /* set semaphore available */
   un.val = 1;
   semctl(semid, 0, SETVAL, un);
   /* first and only semaphore */
   buf.sem_num = 0;
   /* wait if set */
   buf.sem_flg = 0;
	if((pidT=fork())==0)
	{
		if(ap->flag_pro==0)
		{
			exit(0);
		}
	char *argv[]={"Listing3.8a",(char *)0};
		printf("\npidT : %d\n",getpid());
	execv("/home/alpha/zlm/udp/chapter3/ch3/Listing3.8a",argv);
	}
   if((pidD = fork()) == 0)   /* DEPOSITS */
   {
	printf("pid for D: %d\n",getpid());
      /* attach parent's shared memory */
      ap = (struct area *) shmat(shmid, 0, 0);
      /* note: shmid is still set correctly */

      /* handle deposit */
      while(1)
      {
         sleep(1);
//printf("in subprocess d\n");
         /* set semaphore */
         buf.sem_op = -1;
         semop(semid, (struct sembuf *) &buf, 1);
	if(ap->flag_pro==1)
	{
		printf("\nin the D -2 \n");
		
		ap->flag_pro=0;
	}
         if(ap->deposit < 0)
            break; /* exit req */
	
         if(ap->deposit > 0)
         {
            /* handle the deposit */
            ap->balance += ap->deposit;
            ap->deposit = 0; /* clear it */
         }

         /* clear semaphore */
         buf.sem_op = 1;
         semop(semid, (struct sembuf *) &buf, 1);
      }
	printf("\npid for D%d\n",getpid());
      /* child task exits normally */
      exit(0);
   }

   if((pidW = fork()) == 0)   /* WITHDRAWALS */
   {
      /* attach parent's shared memory */
      ap = (struct area *) shmat(shmid, 0, 0);
      /* note: shmid is still set correctly */

      /* handle withdrawal */
      while(1)
      {
         sleep(1);
//printf("in suprocess w\n");
         /* set semaphore */
         buf.sem_op = -1;
         semop(semid, (struct sembuf *) &buf, 1);

         if(ap->withdrawal < 0)
            break; /* exit signal */

         if(ap->withdrawal > 0)
         {
            /* handle the withdrawal */
            ap->balance -= ap->withdrawal;
            ap->withdrawal = 0; /* clear it */
         }

         /* clear semaphore */
         buf.sem_op = 1;
         semop(semid, (struct sembuf *) &buf, 1);
      }
	printf("\npid for W%d\n",getpid());
      /* child task exits normally */
      exit(0);
   }

   /* parent: handle deposit and withdrawal transactions */
   printf("\n\n\n\tWELCOME TO THE FIRST INTERACTIVE BANK\n\n");
   while(1)
   {
     printf("in parent process.. \n");
       printf("\nEnter D for deposit, W for withdrawal: ");
      fflush(stdout);
      fgets(inbuf, sizeof(inbuf), stdin);
      if(inbuf[0] == 'D' || inbuf[0] == 'd')
      {
         printf("\tCurrent account balance is $%d\n", ap->balance);
         printf("\tEnter deposit amount (0 to exit): ");
         fflush(stdout);
         fgets(inbuf, sizeof(inbuf), stdin);

         /* set the semaphore */
         buf.sem_op = -1;
         semop(semid, (struct sembuf *) &buf, 1);

         amount = atoi(inbuf);
        if(amount <= 0) /* exit requested */
         {
            /* signal subtasks */
		ap->flag_pro=0;
            ap->deposit = -1;
            ap->withdrawal = -1;
            break; /* exit infinite loop */
         }
         ap->deposit = amount; /* deposit it */

         /* clear semaphore */
         buf.sem_op = 1;
         semop(semid, (struct sembuf *) &buf, 1);
      }
      else if(inbuf[0] == 'W' || inbuf[0] == 'w')
      {
         printf("\tCurrent account balance is $%d\n", ap->balance);
         printf("\tEnter withdrawal amount (0 to exit): ");
         fflush(stdout);
         fgets(inbuf, sizeof(inbuf), stdin);

         /* set the semaphore */
         buf.sem_op = -1;
         semop(semid, (struct sembuf *) &buf, 1);

         amount = atoi(inbuf);
         if(amount <= 0) /* exit requested */
         {
            /* signal subtasks */
		ap->flag_pro=0;
            ap->deposit = -1;
            ap->withdrawal = -1;
            break; /* exit infinite loop */
         }
         else if(amount <= ap->balance)
         {
            ap->withdrawal = amount; /* withdraw it */
         }
         else
         {
            printf("ERROR: Insufficient funds!\n");
         }

         /* clear semaphore */
         buf.sem_op = 1;
         semop(semid, (struct sembuf *) &buf, 1);
      }
      else
      {
         printf("Invalid transaction code '%c'\n", inbuf[0]);
      }
   }

   /* await child exits */
   waitpid(pidD);
   waitpid(pidW);

   printf("\nYour final account balance is %d\nBye!\n\n", ap->balance);

   /* remove shared memory, semaphore, and exit */
   shmctl(shmid, IPC_RMID, (struct shmid_ds *) 0);
   semctl(semid, 0, IPC_RMID, un);
   return;
}