I need some algorithm help with a multithreaded program I'm writing. It's basically the cp command in unix, but with a read thread and a write thread. I'm using semaphores for thread synchronization. I have structs for buffer and thread data defined as
struct bufType {
char buf[BUFFER_SIZE];
int numBytes;
};
struct threadData {
int fd;
bufType buf;
};
and a global array of bufType. Code for my main is
int main(int argc, const char * argv[])
{
int in, out;
pthread_t Producer, Consumer;
threadData producerData, consumerData;
if (argc != 3)
{
cout << "Error: incorrect number of params" << endl;
exit(0);
}
if ((in = open(argv[1], O_RDONLY, 0666)) == -1)
{
cout << "Error: cannot open input file" << endl;
exit(0);
}
if ((out = open(argv[2], O_WRONLY | O_CREAT, 0666)) == -1)
{
cout << "Cannot create output file" << endl;
exit(0);
}
sem_init(&sem_empty, 0, NUM_BUFFERS);
sem_init(&sem_full, 0, 0);
pthread_create (&Producer, NULL, read_thread, (void *) &producerData);
pthread_create (&Consumer, NULL, write_thread, (void *) &consumerData);
pthread_join(Producer, NULL);
pthread_join(Consumer, NULL);
return 0;
}
and read and write threads:
void *read_thread(void *data)
{
threadData *thread_data;
thread_data = (threadData *) data;
while((thread_data->buf.numBytes = slow_read(thread_data->fd, thread_data->buf.buf, BUFFER_SIZE)) != 0)
{
sem_post(&sem_full);
sem_wait(&sem_empty);
}
pthread_exit(0);
}
void *write_thread(void *data)
{
threadData *thread_data;
thread_data = (threadData *) data;
sem_wait(&sem_full);
slow_write(thread_data->fd, thread_data->buf.buf, thread_data->buf.numBytes);
sem_post(&sem_empty);
pthread_exit(0);
}
So my issue is in what to assign to my threadData variables in main, and my semaphore logic in the read and write threads. I appreciate any help you're able to give