+int
+do_zero_device (const char *device)
+{
+ int64_t ssize = do_blockdev_getsize64 (device);
+ if (ssize == -1)
+ return -1;
+ uint64_t size = (uint64_t) ssize;
+
+ int fd = open (device, O_WRONLY);
+ if (fd == -1) {
+ reply_with_perror ("%s", device);
+ return -1;
+ }
+
+ char buf[1024*1024];
+ memset (buf, 0, sizeof buf);
+
+ uint64_t pos = 0;
+
+ while (pos < size) {
+ uint64_t n64 = size - pos;
+ size_t n;
+ if (n64 > sizeof buf)
+ n = sizeof buf;
+ else
+ n = (size_t) n64; /* safe because of if condition */
+
+ ssize_t r = write (fd, buf, n);
+ if (r == -1) {
+ reply_with_perror ("write: %s (with %" PRId64 " bytes left to write)",
+ device, size);
+ close (fd);
+ return -1;
+ }
+
+ pos += r;
+ notify_progress (pos, size);
+ }
+
+ if (close (fd) == -1) {
+ reply_with_perror ("close: %s", device);
+ return -1;
+ }