src/common/pubsub.c

   1 /* Copyright (c) 2016, The Tor Project, Inc. */
   2 /* See LICENSE for licensing information */
   3
   4 /**
   5  * \file pubsub.c
   6  *
   7  * \brief DOCDOC
   8  */
   9
  10 #include "orconfig.h"
  11 #include "pubsub.h"
  12 #include "container.h"
  13
  14 /** Helper: insert <b>s</b> into <b>topic's</b> list of subscribers, keeping
  15  * them sorted in priority order. */
  16 static void
  17 subscriber_insert(pubsub_topic_t *topic, pubsub_subscriber_t *s)
  18 {
  19   int i;
  20   smartlist_t *sl = topic->subscribers;
  21   for (i = 0; i < smartlist_len(sl); ++i) {
  22     pubsub_subscriber_t *other = smartlist_get(sl, i);
  23     if (s->priority < other->priority) {
  24       break;
  25     }
  26   }
  27   smartlist_insert(sl, i, s);
  28 }
  29
  30 /**
  31  * Add a new subscriber to <b>topic</b>, where (when an event is triggered),
  32  * we'll notify the function <b>fn</b> by passing it <b>subscriber_data</b>.
  33  * Return a handle to the subscribe which can later be passed to
  34  * pubsub_unsubscribe_().
  35  *
  36  * Functions are called in priority order, from lowest to highest.
  37  *
  38  * See pubsub.h for <b>subscribe_flags</b>.
  39  */
  40 const pubsub_subscriber_t *
  41 pubsub_subscribe_(pubsub_topic_t *topic,
  42                   pubsub_subscriber_fn_t fn,
  43                   void *subscriber_data,
  44                   unsigned subscribe_flags,
  45                   unsigned priority)
  46 {
  47   tor_assert(! topic->locked);
  48   if (subscribe_flags & SUBSCRIBE_ATSTART) {
  49     tor_assert(topic->n_events_fired == 0);
  50   }
  51   pubsub_subscriber_t *r = tor_malloc_zero(sizeof(*r));
  52   r->priority = priority;
  53   r->subscriber_flags = subscribe_flags;
  54   r->fn = fn;
  55   r->subscriber_data = subscriber_data;
  56   if (topic->subscribers == NULL) {
  57     topic->subscribers = smartlist_new();
  58   }
  59   subscriber_insert(topic, r);
  60   return r;
  61 }
  62
  63 /**
  64  * Remove the subscriber <b>s</b> from <b>topic</b>.  After calling this
  65  * function, <b>s</b> may no longer be used.
  66  */
  67 int
  68 pubsub_unsubscribe_(pubsub_topic_t *topic,
  69                     const pubsub_subscriber_t *s)
  70 {
  71   tor_assert(! topic->locked);
  72   smartlist_t *sl = topic->subscribers;
  73   if (sl == NULL)
  74     return -1;
  75   int i = smartlist_pos(sl, s);
  76   if (i == -1)
  77     return -1;
  78   pubsub_subscriber_t *tmp = smartlist_get(sl, i);
  79   tor_assert(tmp == s);
  80   smartlist_del_keeporder(sl, i);
  81   tor_free(tmp);
  82   return 0;
  83 }
  84
  85 /**
  86  * For every subscriber s in <b>topic</b>, invoke notify_fn on s and
  87  * event_data.  Return 0 if there were no nonzero return values, and -1 if
  88  * there were any.
  89  */
  90 int
  91 pubsub_notify_(pubsub_topic_t *topic, pubsub_notify_fn_t notify_fn,
  92                void *event_data, unsigned notify_flags)
  93 {
  94   tor_assert(! topic->locked);
  95   (void) notify_flags;
  96   smartlist_t *sl = topic->subscribers;
  97   int n_bad = 0;
  98   ++topic->n_events_fired;
  99   if (sl == NULL)
 100     return -1;
 101   topic->locked = 1;
 102   SMARTLIST_FOREACH_BEGIN(sl, pubsub_subscriber_t *, s) {
 103     int r = notify_fn(s, event_data);
 104     if (r != 0)
 105       ++n_bad;
 106   } SMARTLIST_FOREACH_END(s);
 107   topic->locked = 0;
 108   return (n_bad == 0) ? 0 : -1;
 109 }
 110
 111 /**
 112  * Release all storage held by <b>topic</b>.
 113  */
 114 void
 115 pubsub_clear_(pubsub_topic_t *topic)
 116 {
 117   tor_assert(! topic->locked);
 118
 119   smartlist_t *sl = topic->subscribers;
 120   if (sl == NULL)
 121     return;
 122   SMARTLIST_FOREACH_BEGIN(sl, pubsub_subscriber_t *, s) {
 123     tor_free(s);
 124   } SMARTLIST_FOREACH_END(s);
 125   smartlist_free(sl);
 126   topic->subscribers = NULL;
 127   topic->n_events_fired = 0;
 128 }
 129