[PATCH 3/3] RFC: libxl: internal API for event handling

[Ian Jackson <ian.jackson@eu.citrix.com>]

This is a proposed internal API for other parts of libxl to use when
dealing with events (both osevents and API events ie libxl_event).

There will probably also be some helper functions for
libxl_awaiting_*.

THIS PATCH IS AN RFC AND SHOULD NOT BE APPLIED.  It contains only the
suggested changes to libxl_internal.h, and not any of the necessary
implementation nor consequential changes.
---
 tools/libxl/libxl_internal.h |   52 ++++++++++++++++++++++++++++++++++++++++++
 1 files changed, 52 insertions(+), 0 deletions(-)

diff --git a/tools/libxl/libxl_internal.h b/tools/libxl/libxl_internal.h
index 579188e..8eaf85a 100644
--- a/tools/libxl/libxl_internal.h
+++ b/tools/libxl/libxl_internal.h
@@ -165,6 +165,58 @@ _hidden char **libxl__xs_directory(libxl__gc *gc, xs_transaction_t t,
                                    char *path, unsigned int *nb);
    /* On error: returns NULL, sets errno (no logging) */
 
+
+/* Event handling functions provided by the libxl event core to the
+ * rest of libxl.  Implemented in terms of _beforepoll/_afterpoll
+ * and/or the fd registration machinery, as provided by the
+ * application.
+ *
+ * Semantics are similar to those of the fd and timeout registration
+ * functions provided to libxl_osevent_register_hooks.
+ *
+ * Non-0 returns from libxl__ev_{modify,deregister} have already been
+ * logged by the core and should be returned unmodified to libxl's
+ * caller; NB that they may be valid libxl error codes but they may
+ * also be positive numbers supplied by the caller.
+ */
+
+typedef struct libxl__ev_fd libxl__ev_fd;
+typedef void libxl__ev_fd_callback(libxl__gc *gc, libxl__ev_fd *ev,
+                                   int fd, short events, short revents,
+                                   void *for_callback);
+
+int libxl__ev_fd_register(libxl__gc*, libxl__ev_fd *ev_out,
+                          int fd, short events,
+                          libxl__ev_fd_callback*, void *for_callback);
+int libxl__ev_fd_modify(libxl__gc*, libxl__ev_fd *ev,
+                        short events);
+void libxl__ev_fd_deregister(libxl__gc*, libxl__ev_fd *ev);
+
+typedef struct libxl__ev_time libxl__ev_time;
+typedef void libxl__ev_time_callback(libxl__gc *gc, libxl__ev_fd *ev,
+                                     void *for_callback);
+
+int libxl__ev_time_register(libxl__gc*, libxl__ev_fd *ev_out,
+                            int milliseconds,
+                            libxl__ev_time_callback*, void *for_callback);
+int libxl__ev_time_modify(libxl__gc*, libxl__ev_fd *ev,
+                          int milliseconds);
+void libxl__ev_time_deregister(libxl__gc*, libxl__ev_time *ev);
+
+
+void libxl__event_occured(libxl__gc*, libxl_event *event);
+  /* Arranges to notify the application that the event has occurred.
+   * event should be suitable for passing to libxl_event_free. */
+
+void libxl__event_disaster(libxl__gc*, const char *msg, int errnoval,
+                           libxl_event_type type /* may be 0 */);
+  /* See the "disaster" argument to libxl_event_register_callbacks.
+   * NB that this function may return and the caller isn't supposed to
+   * then crash, although it may fail (and henceforth leave things in
+   * a state where many or all calls fail).
+   */
+
+
 /* from xl_dom */
 _hidden int libxl__domain_is_hvm(libxl__gc *gc, uint32_t domid);
 _hidden int libxl__domain_shutdown_reason(libxl__gc *gc, uint32_t domid);
-- 
1.5.6.5