+
+static char zero[BUFSIZ];
+
+int
+do_is_zero (const char *path)
+{
+ int fd;
+ char buf[BUFSIZ];
+ ssize_t r;
+
+ CHROOT_IN;
+ fd = open (path, O_RDONLY);
+ CHROOT_OUT;
+
+ if (fd == -1) {
+ reply_with_perror ("open: %s", path);
+ return -1;
+ }
+
+ while ((r = read (fd, buf, sizeof buf)) > 0) {
+ if (memcmp (buf, zero, r) != 0) {
+ close (fd);
+ return 0;
+ }
+ }
+
+ if (r == -1) {
+ reply_with_perror ("read: %s", path);
+ close (fd);
+ return -1;
+ }
+
+ if (close (fd) == -1) {
+ reply_with_perror ("close: %s", path);
+ return -1;
+ }
+
+ return 1;
+}
+
+int
+do_is_zero_device (const char *device)
+{
+ int fd;
+ char buf[BUFSIZ];
+ ssize_t r;
+
+ fd = open (device, O_RDONLY);
+ if (fd == -1) {
+ reply_with_perror ("open: %s", device);
+ return -1;
+ }
+
+ while ((r = read (fd, buf, sizeof buf)) > 0) {
+ if (memcmp (buf, zero, r) != 0) {
+ close (fd);
+ return 0;
+ }
+ }
+
+ if (r == -1) {
+ reply_with_perror ("read: %s", device);
+ close (fd);
+ return -1;
+ }
+
+ if (close (fd) == -1) {
+ reply_with_perror ("close: %s", device);
+ return -1;
+ }
+
+ return 1;
+}