#include <shm.h>
int main(int argc,char **argv)
{
int num;
int shmid_goods,shmid_index,semid;
char* shmaddr=NULL;
int* indexaddr=NULL;
int is_noexist=0;
num=10;
//create a shared memory as goods buffer
if((shmid_goods=createshm(".",'s',num))==-1)
{
if(errno==EEXIST)
{
if((shmid_goods=openshm(".",'s'))==-1)
{
exit(1);
}
}
else
{
perror("create shared memory failed\n");
exit(1);
}
}
//attach the shared memory to the current process
if((shmaddr=shmat(shmid_goods,(char*)0,0))==(char*)-1)
{
perror("attach shared memory error\n");
exit(1);
}
//create a shared memory as index
if((shmid_index=createshm(".",'z',2))==-1)
{
if(errno==EEXIST)
{
if((shmid_index=openshm(".",'z'))==-1)
{
exit(1);
}
}
else
{
perror("create shared memory failed\n");
exit(1);
}
}
else
{
is_noexist=1;
}
//attach the shared memory to the current process
if((indexaddr=shmat(shmid_index,(int*)0,0))==(int*)-1)
{
perror("attach shared memory error\n");
exit(1);
}
if(is_noexist)
{
indexaddr[0]=0;
indexaddr[1]=0;
}
//create a semaphore set including 3 semaphores
if((semid=createsem(".",'t',3,0))==-1)
{
if(errno==EEXIST)
{
if((semid=opensem(".",'t'))==-1)
{
exit(1);
}
}
else
{
perror("semget error:");
exit(1);
}
}
else
{
union semun arg;
//seting value for mutex semaphore
arg.val=1;
if(semctl(semid,0,SETVAL,arg)==-1)
{
perror("setting semaphore value failed\n");
return -1;
}
//set value for synchronous semaphore
arg.val=num;
//the num means that the producer can continue to produce num products
if(semctl(semid,1,SETVAL,arg)==-1)
{
perror("setting semaphore value failed\n");
return -1;
}
//the last semaphore's value is default
//the default value '0' means that the consumer is not use any product now
}
int goods=0;
while(1)
{
p(semid,2);
sleep(1);
p(semid,0);
//consumer is consuming a product
goods=shmaddr[indexaddr[1]];
printf("consumer:%d consumes a product[%d]:%d\n",getpid(),indexaddr[1],goods);
indexaddr[1]=(indexaddr[1]+1)%num;
v(semid,0);
sleep(1);
v(semid,1);
}
}
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