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/*
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.
*/
/**
* @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 */
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