netq.h

00001 /* netq.h -- Simple packet queue
00002  *
00003  * Copyright (C) 2010--2012 Olaf Bergmann <bergmann@tzi.org>
00004  *
00005  * This file is part of the library tinyDTLS. Please see the file
00006  * LICENSE for terms of use.
00007  */
00008 
00009 #ifndef _NETQ_H_
00010 #define _NETQ_H_
00011 
00012 #include "config.h"
00013 #include "global.h"
00014 //#include "dtls.h"
00015 #include "time.h"
00016 #include "peer.h"
00017 
00018 /**
00019  * \defgroup netq Network Packet Queue
00020  * The netq utility functions implement an ordered queue of data packets
00021  * to send over the network and can also be used to queue received packets
00022  * from the network.
00023  * @{
00024  */
00025 
00026 #ifndef NETQ_MAXCNT
00027 #define NETQ_MAXCNT 4 /**< maximum number of elements in netq structure */
00028 #endif
00029 
00030 /** 
00031  * Datagrams in the netq_t structure have a fixed maximum size of
00032  * DTLS_MAX_BUF to simplify memory management on constrained nodes. */ 
00033 typedef unsigned char netq_packet_t[DTLS_MAX_BUF];
00034 
00035 typedef struct netq_t {
00036   struct netq_t *next;
00037 
00038   clock_time_t t;           /**< when to send PDU for the next time */
00039   unsigned char retransmit_cnt; /**< retransmission counter, will be removed when zero */
00040   unsigned int timeout;     /**< randomized timeout value */
00041 
00042   dtls_peer_t *peer;        /**< remote address */
00043 
00044   size_t length;        /**< actual length of data */
00045   netq_packet_t data;       /**< the datagram to send */
00046 } netq_t;
00047 
00048 /** 
00049  * Adds a node to the given queue, ordered by their time-stamp t.
00050  * This function returns @c 0 on error, or non-zero if @p node has
00051  * been added successfully.
00052  *
00053  * @param queue A pointer to the queue head where @p node will be added.
00054  * @param node  The new item to add.
00055  * @return @c 0 on error, or non-zero if the new item was added.
00056  */
00057 int netq_insert_node(netq_t **queue, netq_t *node);
00058 
00059 /** Destroys specified node and releases any memory that was allocated
00060  * for the associated datagram. */
00061 void netq_node_free(netq_t *node);
00062 
00063 /** Removes all items from given queue and frees the allocated storage */
00064 void netq_delete_all(netq_t *queue);
00065 
00066 /** Creates a new node suitable for adding to a netq_t queue. */
00067 netq_t *netq_node_new();
00068 
00069 /**
00070  * Returns a pointer to the first item in given queue or NULL if
00071  * empty. 
00072  */
00073 netq_t *netq_head(netq_t **queue);
00074 
00075 /**
00076  * Removes the first item in given queue and returns a pointer to the
00077  * removed element. If queue is empty when netq_pop_first() is called,
00078  * this function returns NULL.
00079  */
00080 netq_t *netq_pop_first(netq_t **queue);
00081 
00082 /**@}*/
00083 
00084 #endif /* _NETQ_H_ */