-extern guestfs_lvm_int_pv_list *parse_command_line_pvs (void);
-extern guestfs_lvm_int_vg_list *parse_command_line_vgs (void);
-extern guestfs_lvm_int_lv_list *parse_command_line_lvs (void);
-
-/* in proto.c */
-extern void main_loop (int sock);
-extern void reply_with_error (const char *fs, ...);
-extern void reply_with_perror (const char *fs, ...);
+extern guestfs_int_lvm_pv_list *parse_command_line_pvs (void);
+extern guestfs_int_lvm_vg_list *parse_command_line_vgs (void);
+extern guestfs_int_lvm_lv_list *parse_command_line_lvs (void);
+
+/*-- in proto.c --*/
+extern void main_loop (int sock) __attribute__((noreturn));
+
+/* ordinary daemon functions use these to indicate errors */
+extern void reply_with_error (const char *fs, ...)
+ __attribute__((format (printf,1,2)));
+extern void reply_with_perror (const char *fs, ...)
+ __attribute__((format (printf,1,2)));
+
+/* daemon functions that receive files (FileIn) should call
+ * receive_file for each FileIn parameter.
+ */
+typedef int (*receive_cb) (void *opaque, const void *buf, int len);
+extern int receive_file (receive_cb cb, void *opaque);
+
+/* daemon functions that receive files (FileIn) can call this
+ * to cancel incoming transfers (eg. if there is a local error),
+ * but they MUST then call reply_with_error or reply_with_perror.
+ */
+extern void cancel_receive (void);
+
+/* daemon functions that return files (FileOut) should call
+ * reply, then send_file_* for each FileOut parameter.
+ * Note max write size if GUESTFS_MAX_CHUNK_SIZE.
+ */
+extern int send_file_write (const void *buf, int len);
+extern int send_file_end (int cancel);
+
+/* only call this if there is a FileOut parameter */