1 files changed, 129 insertions, 0 deletions
diff --git a/src/common/pubsub.c b/src/common/pubsub.c
new file mode 100644
index 0000000000..b3faf40e00
--- /dev/null
+++ b/src/common/pubsub.c
@@ -0,0 +1,129 @@
+/* Copyright (c) 2016, The Tor Project, Inc. */
+/* See LICENSE for licensing information */
+
+/**
+ * \file pubsub.c
+ *
+ * \brief DOCDOC
+ */
+
+#include "orconfig.h"
+#include "pubsub.h"
+#include "container.h"
+
+/** Helper: insert <b>s</b> into <b>topic's</b> list of subscribers, keeping
+ * them sorted in priority order. */
+static void
+subscriber_insert(pubsub_topic_t *topic, pubsub_subscriber_t *s)
+{
+  int i;
+  smartlist_t *sl = topic->subscribers;
+  for (i = 0; i < smartlist_len(sl); ++i) {
+    pubsub_subscriber_t *other = smartlist_get(sl, i);
+    if (s->priority < other->priority) {
+      break;
+    }
+  }
+  smartlist_insert(sl, i, s);
+}
+
+/**
+ * Add a new subscriber to <b>topic</b>, where (when an event is triggered),
+ * we'll notify the function <b>fn</b> by passing it <b>subscriber_data</b>.
+ * Return a handle to the subscribe which can later be passed to
+ * pubsub_unsubscribe_().
+ *
+ * Functions are called in priority order, from lowest to highest.
+ *
+ * See pubsub.h for <b>subscribe_flags</b>.
+ */
+const pubsub_subscriber_t *
+pubsub_subscribe_(pubsub_topic_t *topic,
+                  pubsub_subscriber_fn_t fn,
+                  void *subscriber_data,
+                  unsigned subscribe_flags,
+                  unsigned priority)
+{
+  tor_assert(! topic->locked);
+  if (subscribe_flags & SUBSCRIBE_ATSTART) {
+    tor_assert(topic->n_events_fired == 0);
+  }
+  pubsub_subscriber_t *r = tor_malloc_zero(sizeof(*r));
+  r->priority = priority;
+  r->subscriber_flags = subscribe_flags;
+  r->fn = fn;
+  r->subscriber_data = subscriber_data;
+  if (topic->subscribers == NULL) {
+    topic->subscribers = smartlist_new();
+  }
+  subscriber_insert(topic, r);
+  return r;
+}
+
+/**
+ * Remove the subscriber <b>s</b> from <b>topic</b>.  After calling this
+ * function, <b>s</b> may no longer be used.
+ */
+int
+pubsub_unsubscribe_(pubsub_topic_t *topic,
+                    const pubsub_subscriber_t *s)
+{
+  tor_assert(! topic->locked);
+  smartlist_t *sl = topic->subscribers;
+  if (sl == NULL)
+    return -1;
+  int i = smartlist_pos(sl, s);
+  if (i == -1)
+    return -1;
+  pubsub_subscriber_t *tmp = smartlist_get(sl, i);
+  tor_assert(tmp == s);
+  smartlist_del_keeporder(sl, i);
+  tor_free(tmp);
+  return 0;
+}
+
+/**
+ * For every subscriber s in <b>topic</b>, invoke notify_fn on s and
+ * event_data.  Return 0 if there were no nonzero return values, and -1 if
+ * there were any.
+ */
+int
+pubsub_notify_(pubsub_topic_t *topic, pubsub_notify_fn_t notify_fn,
+               void *event_data, unsigned notify_flags)
+{
+  tor_assert(! topic->locked);
+  (void) notify_flags;
+  smartlist_t *sl = topic->subscribers;
+  int n_bad = 0;
+  ++topic->n_events_fired;
+  if (sl == NULL)
+    return -1;
+  topic->locked = 1;
+  SMARTLIST_FOREACH_BEGIN(sl, pubsub_subscriber_t *, s) {
+    int r = notify_fn(s, event_data);
+    if (r != 0)
+      ++n_bad;
+  } SMARTLIST_FOREACH_END(s);
+  topic->locked = 0;
+  return (n_bad == 0) ? 0 : -1;
+}
+
+/**
+ * Release all storage held by <b>topic</b>.
+ */
+void
+pubsub_clear_(pubsub_topic_t *topic)
+{
+  tor_assert(! topic->locked);
+
+  smartlist_t *sl = topic->subscribers;
+  if (sl == NULL)
+    return;
+  SMARTLIST_FOREACH_BEGIN(sl, pubsub_subscriber_t *, s) {
+    tor_free(s);
+  } SMARTLIST_FOREACH_END(s);
+  smartlist_free(sl);
+  topic->subscribers = NULL;
+  topic->n_events_fired = 0;
+}
+