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#include <semaphore.h>
#include <sys/mman.h>
#include <limits.h>
#include <fcntl.h>
#include <unistd.h>
#include <string.h>
#include <stdarg.h>
#include <errno.h>
#include <time.h>
#include <stdio.h>
#include <sys/stat.h>
#include <stdlib.h>
#include <pthread.h>
static struct {
ino_t ino;
sem_t *sem;
int refcnt;
} *semtab;
static int semcnt;
static pthread_spinlock_t lock;
static pthread_once_t once;
static void init()
{
semtab = calloc(sizeof *semtab, SEM_NSEMS_MAX);
}
static sem_t *find_map(ino_t ino)
{
int i;
for (i=0; i<SEM_NSEMS_MAX && semtab[i].ino != ino; i++);
if (i==SEM_NSEMS_MAX) return 0;
if (semtab[i].refcnt == INT_MAX) return (sem_t *)-1;
semtab[i].refcnt++;
return semtab[i].sem;
}
sem_t *sem_open(const char *name, int flags, ...)
{
va_list ap;
mode_t mode;
unsigned value;
int fd, tfd, dir;
sem_t newsem;
void *map;
char tmp[64];
struct timespec ts;
struct stat st;
int i;
while (*name=='/') name++;
if (strchr(name, '/')) {
errno = EINVAL;
return SEM_FAILED;
}
pthread_once(&once, init);
if (!semtab) {
errno = ENOMEM;
return SEM_FAILED;
}
if (flags & O_CREAT) {
va_start(ap, flags);
mode = va_arg(ap, mode_t) & 0666;
value = va_arg(ap, unsigned);
va_end(ap);
if (value > SEM_VALUE_MAX) {
errno = EINVAL;
return SEM_FAILED;
}
sem_init(&newsem, 1, value);
clock_gettime(CLOCK_REALTIME, &ts);
snprintf(tmp, sizeof(tmp), "/dev/shm/%p-%p-%d-%d",
&name, name, (int)getpid(), (int)ts.tv_nsec);
tfd = open(tmp, O_CREAT|O_EXCL|O_RDWR|O_CLOEXEC, mode);
if (tfd<0) return SEM_FAILED;
dir = open("/dev/shm", O_DIRECTORY|O_RDONLY|O_CLOEXEC);
if (dir<0 || write(tfd,&newsem,sizeof newsem)!=sizeof newsem) {
if (dir >= 0) close(dir);
close(tfd);
unlink(tmp);
return SEM_FAILED;
}
}
flags &= ~O_ACCMODE;
flags |= O_RDWR;
pthread_spin_lock(&lock);
for (;;) {
if (!(flags & O_EXCL)) {
fd = shm_open(name, flags&~O_CREAT, 0);
if (fd >= 0 || errno != ENOENT) {
if (flags & O_CREAT) {
close(dir);
close(tfd);
unlink(tmp);
}
if (fd >= 0 && fstat(fd, &st) < 0) {
close(fd);
fd = -1;
}
if (fd < 0) {
pthread_spin_unlock(&lock);
return SEM_FAILED;
}
if ((map = find_map(st.st_ino))) {
pthread_spin_unlock(&lock);
close(fd);
if (map == (sem_t *)-1)
return SEM_FAILED;
return map;
}
break;
}
}
if (!(flags & O_CREAT)) {
pthread_spin_unlock(&lock);
return SEM_FAILED;
}
if (!linkat(AT_FDCWD, tmp, dir, name, 0)) {
fd = tfd;
close(dir);
unlink(tmp);
break;
}
if ((flags & O_EXCL) || errno != EEXIST) {
close(dir);
close(tfd);
unlink(tmp);
return SEM_FAILED;
}
}
if (fstat(fd, &st) < 0) {
pthread_spin_unlock(&lock);
close(fd);
return SEM_FAILED;
}
if (semcnt == SEM_NSEMS_MAX) {
pthread_spin_unlock(&lock);
close(fd);
errno = EMFILE;
return SEM_FAILED;
}
for (i=0; i<SEM_NSEMS_MAX && semtab[i].sem; i++);
map = mmap(0, sizeof(sem_t), PROT_READ|PROT_WRITE, MAP_SHARED, fd, 0);
close(fd);
if (map == MAP_FAILED) {
pthread_spin_unlock(&lock);
return SEM_FAILED;
}
semtab[i].ino = st.st_ino;
semtab[i].sem = map;
semtab[i].refcnt = 1;
pthread_spin_unlock(&lock);
return map;
}
int sem_close(sem_t *sem)
{
int i;
pthread_spin_lock(&lock);
for (i=0; i<SEM_NSEMS_MAX && semtab[i].sem != sem; i++);
if (!--semtab[i].refcnt) {
semtab[i].sem = 0;
semtab[i].ino = 0;
}
pthread_spin_unlock(&lock);
return munmap(sem, sizeof *sem);
}
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