1 files changed, 228 insertions, 0 deletions

diff --git a/src/lib/util/nc.c b/src/lib/util/nc.c
new file mode 100644
index 000000000..2a612917c
--- /dev/null
+++ b/src/lib/util/nc.c
@@ -0,0 +1,228 @@
+/*
+     This file is part of GNUnet.
+     Copyright (C) 2010, 2016 GNUnet e.V.
+
+     GNUnet is free software: you can redistribute it and/or modify it
+     under the terms of the GNU Affero General Public License as published
+     by the Free Software Foundation, either version 3 of the License,
+     or (at your option) any later version.
+
+     GNUnet 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
+     Affero General Public License for more details.
+
+     You should have received a copy of the GNU Affero General Public License
+     along with this program.  If not, see <http://www.gnu.org/licenses/>.
+
+     SPDX-License-Identifier: AGPL3.0-or-later
+ */
+
+/**
+ * @file util/nc.c
+ * @brief convenience functions for transmission of
+ *        messages to multiple clients
+ * @author Christian Grothoff
+ */
+
+
+#include "platform.h"
+#include "gnunet_util_lib.h"
+
+#define LOG(kind, ...) GNUNET_log_from (kind, "util-nc", __VA_ARGS__)
+
+
+/**
+ * Lists of subscribers we manage for notifications.
+ */
+struct SubscriberList
+{
+  /**
+   * This is a doubly linked list.
+   */
+  struct SubscriberList *next;
+
+  /**
+   * This is a doubly linked list.
+   */
+  struct SubscriberList *prev;
+
+  /**
+   * Overall context this subscriber belongs to.
+   */
+  struct GNUNET_NotificationContext *nc;
+
+  /**
+   * Handle where we registered with @e mq to be told about
+   * the MQ's destruction.
+   */
+  struct GNUNET_MQ_DestroyNotificationHandle *mq_nh;
+
+  /**
+   * Message queue for the subscriber.
+   */
+  struct GNUNET_MQ_Handle *mq;
+};
+
+
+/**
+ * The notification context is the key datastructure for a convenience
+ * API used for transmission of notifications to the subscriber until the
+ * subscriber disconnects (or the notification context is destroyed, in
+ * which case we disconnect these subscribers).  Essentially, all
+ * (notification) messages are queued up until the subscriber is able to
+ * read them.
+ */
+struct GNUNET_NotificationContext
+{
+  /**
+   * Head of list of subscribers receiving notifications.
+   */
+  struct SubscriberList *subscribers_head;
+
+  /**
+   * Tail of list of subscribers receiving notifications.
+   */
+  struct SubscriberList *subscribers_tail;
+
+  /**
+   * Maximum number of optional messages to queue per subscriber.
+   */
+  unsigned int queue_length;
+};
+
+
+/**
+ * Subscriber has disconnected, clean up.
+ *
+ * @param cls our `struct SubscriberList *`
+ */
+static void
+handle_mq_destroy (void *cls)
+{
+  struct SubscriberList *pos = cls;
+  struct GNUNET_NotificationContext *nc = pos->nc;
+
+  GNUNET_CONTAINER_DLL_remove (nc->subscribers_head,
+                               nc->subscribers_tail,
+                               pos);
+  GNUNET_free (pos);
+}
+
+
+/**
+ * Create a new notification context.
+ *
+ * @param queue_length maximum number of messages to keep in
+ *        the notification queue; optional messages are dropped
+ *        if the queue gets longer than this number of messages
+ * @return handle to the notification context
+ */
+struct GNUNET_NotificationContext *
+GNUNET_notification_context_create (unsigned int queue_length)
+{
+  struct GNUNET_NotificationContext *nc;
+
+  nc = GNUNET_new (struct GNUNET_NotificationContext);
+  nc->queue_length = queue_length;
+  return nc;
+}
+
+
+/**
+ * Destroy the context, force disconnect for all subscribers.
+ *
+ * @param nc context to destroy.
+ */
+void
+GNUNET_notification_context_destroy (struct GNUNET_NotificationContext *nc)
+{
+  struct SubscriberList *pos;
+
+  while (NULL != (pos = nc->subscribers_head))
+  {
+    GNUNET_CONTAINER_DLL_remove (nc->subscribers_head,
+                                 nc->subscribers_tail,
+                                 pos);
+    GNUNET_MQ_destroy_notify_cancel (pos->mq_nh);
+    GNUNET_free (pos);
+  }
+  GNUNET_free (nc);
+}
+
+
+/**
+ * Add a subscriber to the notification context.
+ *
+ * @param nc context to modify
+ * @param mq message queue add
+ */
+void
+GNUNET_notification_context_add (struct GNUNET_NotificationContext *nc,
+                                 struct GNUNET_MQ_Handle *mq)
+{
+  struct SubscriberList *cl;
+
+  for (cl = nc->subscribers_head; NULL != cl; cl = cl->next)
+    if (cl->mq == mq)
+      return;
+  /* already present */
+  cl = GNUNET_new (struct SubscriberList);
+  GNUNET_CONTAINER_DLL_insert (nc->subscribers_head,
+                               nc->subscribers_tail,
+                               cl);
+  cl->nc = nc;
+  cl->mq = mq;
+  cl->mq_nh = GNUNET_MQ_destroy_notify (cl->mq,
+                                        &handle_mq_destroy,
+                                        cl);
+}
+
+
+/**
+ * Send a message to all subscribers of this context.
+ *
+ * @param nc context to modify
+ * @param msg message to send
+ * @param can_drop can this message be dropped due to queue length limitations
+ */
+void
+GNUNET_notification_context_broadcast (struct GNUNET_NotificationContext *nc,
+                                       const struct GNUNET_MessageHeader *msg,
+                                       int can_drop)
+{
+  struct SubscriberList *pos;
+  struct GNUNET_MQ_Envelope *env;
+
+  for (pos = nc->subscribers_head; NULL != pos; pos = pos->next)
+  {
+    if ((GNUNET_YES == can_drop) &&
+        (GNUNET_MQ_get_length (pos->mq) > nc->queue_length))
+      continue;
+    env = GNUNET_MQ_msg_copy (msg);
+    GNUNET_MQ_send (pos->mq,
+                    env);
+  }
+}
+
+
+/**
+ * Return active number of subscribers in this context.
+ *
+ * @param nc context to query
+ * @return number of current subscribers
+ */
+unsigned int
+GNUNET_notification_context_get_size (struct GNUNET_NotificationContext *nc)
+{
+  unsigned int num;
+  struct SubscriberList *pos;
+
+  num = 0;
+  for (pos = nc->subscribers_head; NULL != pos; pos = pos->next)
+    num++;
+  return num;
+}
+
+
+/* end of nc.c */