+char *join(const char *x, ...) {
+ va_list ap;
+ size_t l;
+ char *r, *p;
+
+ va_start(ap, x);
+
+ if (x) {
+ l = strlen(x);
+
+ for (;;) {
+ const char *t;
+
+ t = va_arg(ap, const char *);
+ if (!t)
+ break;
+
+ l += strlen(t);
+ }
+ } else
+ l = 0;
+
+ va_end(ap);
+
+ r = new(char, l+1);
+ if (!r)
+ return NULL;
+
+ if (x) {
+ p = stpcpy(r, x);
+
+ va_start(ap, x);
+
+ for (;;) {
+ const char *t;
+
+ t = va_arg(ap, const char *);
+ if (!t)
+ break;
+
+ p = stpcpy(p, t);
+ }
+
+ va_end(ap);
+ } else
+ r[0] = 0;
+
+ return r;
+}
+
+bool is_main_thread(void) {
+ static __thread int cached = 0;
+
+ if (_unlikely_(cached == 0))
+ cached = getpid() == gettid() ? 1 : -1;
+
+ return cached > 0;
+}
+
+int block_get_whole_disk(dev_t d, dev_t *ret) {
+ char *p, *s;
+ int r;
+ unsigned n, m;
+
+ assert(ret);
+
+ /* If it has a queue this is good enough for us */
+ if (asprintf(&p, "/sys/dev/block/%u:%u/queue", major(d), minor(d)) < 0)
+ return -ENOMEM;
+
+ r = access(p, F_OK);
+ free(p);
+
+ if (r >= 0) {
+ *ret = d;
+ return 0;
+ }
+
+ /* If it is a partition find the originating device */
+ if (asprintf(&p, "/sys/dev/block/%u:%u/partition", major(d), minor(d)) < 0)
+ return -ENOMEM;
+
+ r = access(p, F_OK);
+ free(p);
+
+ if (r < 0)
+ return -ENOENT;
+
+ /* Get parent dev_t */
+ if (asprintf(&p, "/sys/dev/block/%u:%u/../dev", major(d), minor(d)) < 0)
+ return -ENOMEM;
+
+ r = read_one_line_file(p, &s);
+ free(p);
+
+ if (r < 0)
+ return r;
+
+ r = sscanf(s, "%u:%u", &m, &n);
+ free(s);
+
+ if (r != 2)
+ return -EINVAL;
+
+ /* Only return this if it is really good enough for us. */
+ if (asprintf(&p, "/sys/dev/block/%u:%u/queue", m, n) < 0)
+ return -ENOMEM;
+
+ r = access(p, F_OK);
+ free(p);
+
+ if (r >= 0) {
+ *ret = makedev(m, n);
+ return 0;
+ }
+
+ return -ENOENT;
+}
+
+int file_is_sticky(const char *p) {
+ struct stat st;
+
+ assert(p);
+
+ if (lstat(p, &st) < 0)
+ return -errno;
+
+ return
+ st.st_uid == 0 &&
+ (st.st_mode & S_ISVTX);
+}
+