1 files changed, 81 insertions, 0 deletions
diff --git a/src/core/or/orconn_event.c b/src/core/or/orconn_event.c
new file mode 100644
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+++ b/src/core/or/orconn_event.c
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+/* Copyright (c) 2007-2019, The Tor Project, Inc. */
+/* See LICENSE for licensing information */
+
+/**
+ * \file orconn_event.c
+ * \brief Publish state change messages for OR connections
+ *
+ * Implements a basic publish-subscribe framework for messages about
+ * the state of OR connections.  The publisher calls the subscriber
+ * callback functions synchronously.
+ *
+ * Although the synchronous calls might not simplify the call graph,
+ * this approach improves data isolation because the publisher doesn't
+ * need knowledge about the internals of subscribing subsystems.  It
+ * also avoids race conditions that might occur in asynchronous
+ * frameworks.
+ **/
+
+#include "core/or/or.h"
+#include "lib/subsys/subsys.h"
+
+#define ORCONN_EVENT_PRIVATE
+#include "core/or/orconn_event.h"
+#include "core/or/orconn_event_sys.h"
+
+/** List of subscribers */
+static smartlist_t *orconn_event_rcvrs;
+
+/** Initialize subscriber list */
+static int
+orconn_event_init(void)
+{
+  orconn_event_rcvrs = smartlist_new();
+  return 0;
+}
+
+/** Free subscriber list */
+static void
+orconn_event_fini(void)
+{
+  smartlist_free(orconn_event_rcvrs);
+}
+
+/**
+ * Subscribe to messages about OR connection events
+ *
+ * Register a callback function to receive messages about ORCONNs.
+ * The publisher calls this function synchronously.
+ **/
+void
+orconn_event_subscribe(orconn_event_rcvr_t fn)
+{
+  tor_assert(fn);
+  /* Don't duplicate subscriptions. */
+  if (smartlist_contains(orconn_event_rcvrs, fn))
+    return;
+
+  smartlist_add(orconn_event_rcvrs, fn);
+}
+
+/**
+ * Publish a message about OR connection events
+ *
+ * This calls the subscriber receiver function synchronously.
+ **/
+void
+orconn_event_publish(const orconn_event_msg_t *msg)
+{
+  SMARTLIST_FOREACH_BEGIN(orconn_event_rcvrs, orconn_event_rcvr_t, fn) {
+    tor_assert(fn);
+    (*fn)(msg);
+  } SMARTLIST_FOREACH_END(fn);
+}
+
+const subsys_fns_t sys_orconn_event = {
+  .name = "orconn_event",
+  .supported = true,
+  .level = -33,
+  .initialize = orconn_event_init,
+  .shutdown = orconn_event_fini,
+};