* @param pf	     Pool factory where the memory pool will be created from.
 * @param name	     Optional resolver name to identify the instance in 
 *		     the log.
 * @param options    Optional options, must be zero for now.
 * @param timer	     Optional timer heap instance to be used by the resolver.
 *		     If timer heap is not specified, an internal timer will be
 *		     created, and application would need to poll the resolver
 *		     periodically.
 * @param ioqueue    Optional I/O Queue instance to be used by the resolver.
 *		     If ioqueue is not specified, an internal one will be
 *		     created, and application would need to poll the resolver
 *		     periodically.
 * @param p_resolver Pointer to receive the resolver instance.
 *
 * @return	     PJ_SUCCESS on success, or the appropriate error code,
 */
PJ_DECL(pj_status_t) pj_dns_resolver_create(pj_pool_factory *pf,
					    const char *name,
					    unsigned options,
					    pj_timer_heap_t *timer,
					    pj_ioqueue_t *ioqueue,
					    pj_dns_resolver **p_resolver);


/**
 * Update the name servers for the DNS resolver. The name servers MUST be
 * configured before any resolution can be done. The order of nameservers
 * specifies their priority; the first name server will be tried first
 * before the next in the list.
 *
 * @param resolver  The resolver instance.
 * @param count     Number of name servers in the array.
 * @param servers   Array of name server IP addresses or hostnames. If
 *		    hostname is specified, the hostname must be resolvable
 *		    with pj_gethostbyname().
 * @param ports	    Optional array of ports. If this argument is NULL,
 *		    the nameserver will use default port.
 *
 * @return	    PJ_SUCCESS on success, or the appropriate error code,
 */
PJ_DECL(pj_status_t) pj_dns_resolver_set_ns(pj_dns_resolver *resolver,
					    unsigned count,
					    const pj_str_t servers[],
					    const pj_uint16_t ports[]);


/**
 * Get the resolver current settings.
 *
 * @param resolver  The resolver instance.
 * @param st	    Buffer to be filled up with resolver settings.
 *
 * @return	    The query timeout setting, in seconds.
 */
PJ_DECL(pj_status_t) pj_dns_resolver_get_settings(pj_dns_resolver *resolver,
						  pj_dns_settings *st);


/**
 * Modify the resolver settings. Application should initialize the settings
 * by retrieving current settings first before applying new settings, to
 * ensure that all fields are initialized properly.
 *
 * @param resolver  The resolver instance.
 * @param st	    The resolver settings.
 *
 * @return	    PJ_SUCCESS on success, or the appropriate error code,
 */
PJ_DECL(pj_status_t) pj_dns_resolver_set_settings(pj_dns_resolver *resolver,
						  const pj_dns_settings *st);


/**
 * Poll for events from the resolver. This function MUST be called 
 * periodically when the resolver is using it's own timer or ioqueue
 * (in other words, when NULL is specified as either \a timer or
 * \a ioqueue argument in #pj_dns_resolver_create()).
 *
 * @param resolver  The resolver instance.
 * @param timeout   Maximum time to wait for event occurence. If this
 *		    argument is NULL, this function will wait forever
 *		    until events occur.
 */
PJ_DECL(void) pj_dns_resolver_handle_events(pj_dns_resolver *resolver,
					    const pj_time_val *timeout);


/**
 * Destroy DNS resolver instance.
 *
 * @param resolver  The resolver object to be destryed
 * @param notify    If non-zero, all pending asynchronous queries will be
 *		    cancelled and its callback will be called. If FALSE,
 *		    then no callback will be called.
 *
 * @return	    PJ_SUCCESS on success, or the appropriate error code,
 */
PJ_DECL(pj_status_t) pj_dns_resolver_destroy(pj_dns_resolver *resolver,
					     pj_bool_t notify);


/**
 * Create and start asynchronous DNS query for a single resource. Depending
 * on whether response cache is available, this function will either start
 * an asynchronous DNS query or call the callback immediately.
 *
 * If response is not available in the cache, an asynchronous query will be
 * started, and callback will be called at some time later when the query
 * completes. If \a p_query argument is not NULL, it will be filled with
 * the asynchronous query object.
 *
 * If response is available in the cache, the callback will be called 
 * immediately before this function returns. In this case, if \a p_query
 * argument is not NULL, the value will be set to NULL since no new query
 * is started.
 *
 * @param resolver  The resolver object.
 * @param name	    The name to be resolved.
 * @param type	    The type of resource (see #pj_dns_type constants).
 * @param options   Optional options, must be zero for now.
 * @param cb	    Callback to be called when the query completes,
 *		    either successfully or with failure.
 * @param user_data Arbitrary user data to be associated with the query,
 *		    and which will be given back in the callback.
 * @param p_query   Optional pointer to receive the query object, if one
 *		    was started. If this pointer is specified, a NULL may
 *		    be returned if response cache is available immediately.
 *
 * @return	    PJ_SUCCESS if either an asynchronous query has been 
 *		    started successfully or response cache is available and
 *		    the user callback has been called.
 */
PJ_DECL(pj_status_t) pj_dns_resolver_start_query(pj_dns_resolver *resolver,
						 const pj_str_t *name,
						 int type,
						 unsigned options,
						 pj_dns_callback *cb,
						 void *user_data,
						 pj_dns_async_query **p_query);

/**
 * Cancel a pending query.
 *
 * @param query	    The pending asynchronous query to be cancelled.
 * @param notify    If non-zero, the callback will be called with failure
 *		    status to notify that the query has been cancelled.
 *
 * @return	    PJ_SUCCESS on success, or the appropriate error code,
 */
PJ_DECL(pj_status_t) pj_dns_resolver_cancel_query(pj_dns_async_query *query,
						  pj_bool_t notify);


/**
 * Put the specified DNS packet into DNS cache. This function is mainly used
 * for testing the resolver, however it can also be used to inject entries
 * into the resolver.
 *
 * The packet MUST contain either answer section or query section so that
 * it can be indexed.
 *
 * @param resolver  The resolver instance.
 * @param pkt	    DNS packet to be added to the DNS cache. If the packet
 *		    matches existing entry, it will update the entry.
 * @param set_ttl   If the value is PJ_FALSE, the entry will not expire 
 *		    (so use with care). Otherwise cache expiration will be
 *		    calculated based on the TTL of the answeres.
 *
 * @return	    PJ_SUCCESS on success, or the appropriate error code.
 */
PJ_DECL(pj_status_t) pj_dns_resolver_add_entry(pj_dns_resolver *resolver,
					       const pj_dns_parsed_packet *pkt,
					       pj_bool_t set_ttl);

/**
 * Get the total number of response in the response cache.
 *
 * @param resolver  The resolver instance.
 *
 * @return	    Current number of entries being stored in the response
 *		    cache.
 */
PJ_DECL(unsigned) pj_dns_resolver_get_cached_count(pj_dns_resolver *resolver);


/**
 * Dump resolver state to the log.
 *
 * @param resolver  The resolver instance.
 * @param detail    Will print detailed entries.
 */
PJ_DECL(void) pj_dns_resolver_dump(pj_dns_resolver *resolver,
				   pj_bool_t detail);


/**
 * @}
 */

PJ_END_DECL


#endif	/* __PJLIB_UTIL_RESOLVER_H__ */