+ struct guestfs_message_header hdr;
+ XDR xdr;
+ u_int32_t len;
+ int serial = g->msg_next_serial++;
+ int sent;
+ guestfs_main_loop *ml = guestfs_get_main_loop (g);
+
+ if (g->state != BUSY) {
+ error (g, "guestfs__send_sync: state %d != BUSY", g->state);
+ return -1;
+ }
+
+ /* This is probably an internal error. Or perhaps we should just
+ * free the buffer anyway?
+ */
+ if (g->msg_out != NULL) {
+ error (g, "guestfs__send_sync: msg_out should be NULL");
+ return -1;
+ }
+
+ /* We have to allocate this message buffer on the heap because
+ * it is quite large (although will be mostly unused). We
+ * can't allocate it on the stack because in some environments
+ * we have quite limited stack space available, notably when
+ * running in the JVM.
+ */
+ g->msg_out = safe_malloc (g, GUESTFS_MESSAGE_MAX + 4);
+ xdrmem_create (&xdr, g->msg_out + 4, GUESTFS_MESSAGE_MAX, XDR_ENCODE);
+
+ /* Serialize the header. */
+ hdr.prog = GUESTFS_PROGRAM;
+ hdr.vers = GUESTFS_PROTOCOL_VERSION;
+ hdr.proc = proc_nr;
+ hdr.direction = GUESTFS_DIRECTION_CALL;
+ hdr.serial = serial;
+ hdr.status = GUESTFS_STATUS_OK;
+
+ if (!xdr_guestfs_message_header (&xdr, &hdr)) {
+ error (g, "xdr_guestfs_message_header failed");
+ goto cleanup1;
+ }
+
+ /* Serialize the args. If any, because some message types
+ * have no parameters.
+ */
+ if (xdrp) {
+ if (!(*xdrp) (&xdr, args)) {
+ error (g, "dispatch failed to marshal args");
+ goto cleanup1;
+ }
+ }
+
+ /* Get the actual length of the message, resize the buffer to match
+ * the actual length, and write the length word at the beginning.
+ */
+ len = xdr_getpos (&xdr);
+ xdr_destroy (&xdr);
+
+ g->msg_out = safe_realloc (g, g->msg_out, len + 4);
+ g->msg_out_size = len + 4;
+ g->msg_out_pos = 0;
+
+ xdrmem_create (&xdr, g->msg_out, 4, XDR_ENCODE);
+ xdr_uint32_t (&xdr, &len);
+
+ if (guestfs__switch_to_sending (g) == -1)
+ goto cleanup1;
+
+ sent = 0;
+ guestfs_set_send_callback (g, send_cb, &sent);
+ if (ml->main_loop_run (ml, g) == -1)
+ goto cleanup1;
+ if (sent != 1) {
+ error (g, "send failed, see earlier error messages");
+ goto cleanup1;
+ }
+
+ return serial;
+
+ cleanup1:
+ free (g->msg_out);
+ g->msg_out = NULL;
+ g->msg_out_size = 0;