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#include <stdio.h>
#include <stdlib.h>
#include <pthread.h>
#include <fcntl.h>
#include <unistd.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <sys/mman.h>
#include "shm.h"
#define SHARE_NAME "/ipc.shm"
/* open and return a pointer to shared data */
struct share_data *get_share(void)
{
struct share_data *data;
int fd;
fd = shm_open(SHARE_NAME, O_RDWR, 0);
if (fd == -1)
return NULL;
data = mmap(NULL, sysconf(_SC_PAGESIZE), PROT_READ | PROT_WRITE,
MAP_SHARED, fd, 0);
if (data == MAP_FAILED) {
close(fd);
return NULL;
}
close(fd);
return data;
}
/* initialize shared data */
void init_share(struct share_data *data)
{
pthread_mutexattr_t mattr;
pthread_condattr_t cattr;
pthread_mutexattr_init(&mattr);
pthread_mutexattr_setprotocol(&mattr, PTHREAD_PRIO_INHERIT);
pthread_mutexattr_setpshared(&mattr, PTHREAD_PROCESS_SHARED);
pthread_mutexattr_setrobust(&mattr, PTHREAD_MUTEX_ROBUST);
pthread_mutex_init(&data->m, &mattr);
pthread_condattr_init(&cattr);
pthread_condattr_setpshared(&cattr, PTHREAD_PROCESS_SHARED);
pthread_cond_init(&data->c, &cattr);
}
/* create a zero'd out file of size 1 page */
int create_share(void)
{
int ret;
int fd;
fd = shm_open(SHARE_NAME, O_CREAT|O_RDWR, S_IRUSR|S_IWUSR);
if (fd == -1)
return -1;
ret = ftruncate(fd, sysconf(_SC_PAGESIZE));
close(fd);
return ret;
}
/* remove the share */
void remove_share(void)
{
shm_unlink(SHARE_NAME);
}
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