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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>
static void *find_map(int fd)
{
char c;
struct stat st;
FILE *f;
void *addr;
unsigned long long off, ino;
char buf[100];
if (fstat(fd, &st) < 0) return 0;
if (!(f = fopen("/proc/self/maps", "rb"))) return 0;
while (fgets(buf, sizeof buf, f)) {
sscanf(buf, "%lx-%*lx %*s %llx %*x:%*x %llu /dev/shm%c",
(long *)&addr, &off, &ino, &c);
while (!strchr(buf, '\n') && fgets(buf, sizeof buf, f));
if (c!='/') continue;
c = 0;
if (!off && st.st_ino == ino) {
fclose(f);
return addr;
}
}
fclose(f);
return 0;
}
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;
while (*name=='/') name++;
if (strchr(name, '/')) {
errno = EINVAL;
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, 0, 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, mode);
if (tfd<0) return SEM_FAILED;
dir = open("/dev/shm", O_DIRECTORY|O_RDONLY);
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;
for (;;) {
if (!(flags & O_EXCL)) {
fd = shm_open(name, flags&~O_CREAT, mode);
if (fd >= 0 || errno != ENOENT) {
if (flags & O_CREAT) {
close(dir);
close(tfd);
unlink(tmp);
}
if (fd < 0) return SEM_FAILED;
if ((map = find_map(fd)))
return map;
break;
}
}
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;
}
}
map = mmap(0, sizeof(sem_t), PROT_READ|PROT_WRITE, MAP_SHARED, fd, 0);
close(fd);
if (map == MAP_FAILED) return SEM_FAILED;
return map;
}
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