+/*
+ * Check for existing filesystem or partition table on device.
+ * Returns:
+ * 1 for existing fs or partition
+ * 0 for nothing found
+ * -1 for internal error
+ */
+static int
+check_overwrite(
+ char *device)
+{
+ const char *type;
+ blkid_probe pr = NULL;
+ int ret;
+ blkid_loff_t size;
+
+ if (!device || !*device)
+ return 0;
+
+ ret = -1; /* will reset on success of all setup calls */
+
+ pr = blkid_new_probe_from_filename(device);
+ if (!pr)
+ goto out;
+
+ size = blkid_probe_get_size(pr);
+ if (size < 0)
+ goto out;
+
+ /* nothing to overwrite on a 0-length device */
+ if (size == 0) {
+ ret = 0;
+ goto out;
+ }
+
+ ret = blkid_probe_enable_partitions(pr, 1);
+ if (ret < 0)
+ goto out;
+
+ ret = blkid_do_fullprobe(pr);
+ if (ret < 0)
+ goto out;
+
+ /*
+ * Blkid returns 1 for nothing found and 0 when it finds a signature,
+ * but we want the exact opposite, so reverse the return value here.
+ *
+ * In addition print some useful diagnostics about what actually is
+ * on the device.
+ */
+ if (ret) {
+ ret = 0;
+ goto out;
+ }
+
+ if (!blkid_probe_lookup_value(pr, "TYPE", &type, NULL)) {
+ fprintf(stderr,
+ "%s appears to contain an existing "
+ "filesystem (%s).\n", device, type);
+ } else if (!blkid_probe_lookup_value(pr, "PTTYPE", &type, NULL)) {
+ fprintf(stderr,
+ "%s appears to contain a partition "
+ "table (%s).\n", device, type);
+ } else {
+ fprintf(stderr,
+ "%s appears to contain something weird "
+ "according to blkid\n", device);
+ }
+ ret = 1;
+
+out:
+ if (pr)
+ blkid_free_probe(pr);
+ if (ret == -1)
+ fprintf(stderr,
+ "probe of %s failed, cannot detect "
+ "existing filesystem.\n", device);
+ return ret;
+}
+