共享内存和信号灯集练习-编程知识

共享内存和信号灯集练习

#include <mystdio.h>

int main(int argc, const char *argv[])
{
   //创建key值
   key_t key = ftok("/home/ubuntu",2);
   if(key<0)
   {
       perror("ftok");
       return -1;
   }
   printf("key=%#x\n",key);
   //创建信号灯集
   int semid = semget(key,2,IPC_CREAT|0664);
   if(semid < 0)
   {
       perror("semget");
       return -1;
   }
   //设置信号灯值
   unsigned short brr[2] = {0,1};
   if(semctl(semid,0,SETALL,brr)<0)
   {
       perror("semctl");
       return -1;
   }
   //通过key值寻找共享内存
   int shmid = shmget(key,128,IPC_CREAT|0664);
   if(shmid<0)
   {
       perror("shmget");
       return -1;
   }
   printf("shmid=%#x\n",shmid);
   //将共享内存映射到用户空间
   void* adr = shmat(shmid,NULL,0);
   if((void*)-1 == adr)
   {
       perror("shmat");
       return -1;
   }
   printf("adr = %p\n",adr);

char* ptr = (char*)adr;
strcpy(ptr,"1234567");

   struct sembuf sop;
   while(1)
   {
       sop.sem_num = 1;
       sop.sem_op = -1;
       sop.sem_flg = 0;

       if(semop(semid,&sop,1) < 0)
       {
           perror("semop");
           return -1;
       }
       printf("%s\n",ptr);

       sop.sem_num = 0;
       sop.sem_op = +1;
       sop.sem_flg = 0;

       if(semop(semid,&sop,1) <0)
       {
           perror("semop");
           return -1;
       }
   }

   return 0;
}

#include <mystdio.h>

int main(int argc, const char *argv[])
{
   //找到key值
   key_t key = ftok("/home/ubuntu",2);
   if(key <0)
   {
       perror("ftok");
       return -1;
   }
   printf("key=%#x\n",key);
   //创建信号灯集
   int semid = semget(key,2,IPC_CREAT|0664);
   if(semid < 0)
   {
       perror("semget");
       return -1;
   }

   //通过key值寻找共享内存
   int shmid = shmget(key,128,IPC_CREAT|0664);
   if(shmid<0)
   {
       perror("shmget");
       return -1;
   }
   printf("shmid=%#x\n",shmid);
   //将共享内存映射到用户空间
   void* adr = shmat(shmid,NULL,0);
   if((void*)-1 == adr)
   {
       perror("shmat");
       return -1;
   }
   printf("adr = %p\n",adr);

   char* ptr = (char*)adr;
   char* start = NULL;
   char* end = NULL;

char temp=0;
struct sembuf sop;

   while(1)
   {
       sop.sem_num = 0;
       sop.sem_op = -1;
       sop.sem_flg = 0;

       if(semop(semid,&sop,1)<0)
       {
           perror("semop");
           return -1;
       }

start = ptr;
end = start + strlen(ptr)-1;

       while(start < end)
       {
           temp = *start;
           *start = *end;
           *end = temp;
           start++;
           end--;
       }

       sop.sem_num = 1;
       sop.sem_op = +1;
       sop.sem_flg = 0;
       if(semop(semid,&sop,1) < 0)
       {
           perror("semop");
           return -1;
       }
   }


   return 0;
}