libports: Add ports_request_dead_name_notification ()

This significantly cuts down the boilerplate of
requesting dead-name notifications.

3 files changed, 63 insertions, 1 deletions

diff --git a/libports/Makefile b/libports/Makefile
index 9b483e61..c67d8fec 100644
--- a/libports/Makefile
+++ b/libports/Makefile
@@ -36,7 +36,7 @@ SRCS = create-bucket.c create-class.c \
  interrupt-operation.c interrupt-on-notify.c interrupt-notified-rpcs.c \
  dead-name.c create-port.c import-port.c default-uninhibitable-rpcs.c \
  claim-right.c transfer-right.c create-port-noinstall.c create-internal.c \
- interrupted.c extern-inline.c port-deref-deferred.c
+ interrupted.c extern-inline.c port-deref-deferred.c request-notification.c
 
 installhdrs = ports.h port-deref-deferred.h
 
diff --git a/libports/ports.h b/libports/ports.h
index f8ce9b6c..2d6f6a60 100644
--- a/libports/ports.h
+++ b/libports/ports.h
@@ -322,6 +322,14 @@ void ports_port_deref_weak (void *port);
     __pi ? (__pi->bucket->notify_port == __pi) : 0; \
   })
 
+/* Request a dead-name notification for NAME on behalf of OBJECT.
+   If PREVIOUS is null, deallocate any previously registered port,
+   otherwise return it.  If OBJECT is null, cancel the previously
+   registered notification.  */
+error_t ports_request_dead_name_notification (void *object,
+                                              mach_port_t name,
+                                              mach_port_t *previous);
+
 /* The user is responsible for listening for no senders notifications;
    when one arrives, call this routine for the PORT the message was
    sent to, providing the MSCOUNT from the notification. */
diff --git a/libports/request-notification.c b/libports/request-notification.c
new file mode 100644
index 00000000..c7a7ca25
--- /dev/null
+++ b/libports/request-notification.c
@@ -0,0 +1,54 @@
+/* Request dead-name notifications
+
+   Copyright (C) 2021 Free Software Foundation, Inc.
+
+   Written by Sergey Bugaev <bugaevc@gmail.com>
+
+   This program is free software; you can redistribute it and/or
+   modify it under the terms of the GNU General Public License as
+   published by the Free Software Foundation; either version 2, or (at
+   your option) any later version.
+
+   This program is distributed in the hope that it will be useful, but
+   WITHOUT ANY WARRANTY; without even the implied warranty of
+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+   General Public License for more details.
+
+   You should have received a copy of the GNU General Public License
+   along with this program; if not, write to the Free Software
+   Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA. */
+
+#include "ports.h"
+#include <mach/notify.h>
+
+error_t
+ports_request_dead_name_notification (void *object, mach_port_t name,
+                                      mach_port_t *previous)
+{
+  error_t err;
+  mach_port_t notify_port;
+  mach_port_t prev;
+
+  if (object)
+    notify_port = ports_port_notify_right (object);
+  else
+    notify_port = MACH_PORT_NULL;
+
+  err = mach_port_request_notification (mach_task_self (), name,
+                                        MACH_NOTIFY_DEAD_NAME, 1,
+                                        notify_port,
+                                        MACH_MSG_TYPE_MAKE_SEND_ONCE,
+                                        &prev);
+  if (err)
+    return err;
+
+  if (previous != NULL)
+    *previous = prev;
+  else if (MACH_PORT_VALID (prev))
+    {
+      err = mach_port_deallocate (mach_task_self (), prev);
+      assert_perror_backtrace (err);
+    }
+
+  return 0;
+}