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router.go
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router.go
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/*
* Copyright (c) 2013 IBM Corp.
*
* All rights reserved. This program and the accompanying materials
* are made available under the terms of the Eclipse Public License v1.0
* which accompanies this distribution, and is available at
* http://www.eclipse.org/legal/epl-v10.html
*
* Contributors:
* Seth Hoenig
* Allan Stockdill-Mander
* Mike Robertson
*/
package mqtt
import (
"container/list"
"strings"
"sync"
)
// route is a type which associates MQTT Topic strings with a
// callback to be executed upon the arrival of a message associated
// with a subscription to that topic.
type route struct {
topic string
callback MessageHandler
}
// match takes a slice of strings which represent the route being tested having been split on '/'
// separators, and a slice of strings representing the topic string in the published message, similarly
// split.
// The function determines if the topic string matches the route according to the MQTT topic rules
// and returns a boolean of the outcome
func match(route []string, topic []string) bool {
if len(route) == 0 {
if len(topic) == 0 {
return true
}
return false
}
if len(topic) == 0 {
if route[0] == "#" {
return true
}
return false
}
if route[0] == "#" {
return true
}
if (route[0] == "+") || (route[0] == topic[0]) {
return match(route[1:], topic[1:])
}
return false
}
func routeIncludesTopic(route, topic string) bool {
return match(strings.Split(route, "/"), strings.Split(topic, "/"))
}
// match takes the topic string of the published message and does a basic compare to the
// string of the current Route, if they match it returns true
func (r *route) match(topic string) bool {
return r.topic == topic || routeIncludesTopic(r.topic, topic)
}
type router struct {
sync.RWMutex
routes *list.List
defaultHandler MessageHandler
messages chan *Message
stop chan bool
}
// newRouter returns a new instance of a Router and channel which can be used to tell the Router
// to stop
func newRouter() (*router, chan bool) {
router := &router{routes: list.New(), messages: make(chan *Message), stop: make(chan bool)}
stop := router.stop
return router, stop
}
// addRoute takes a topic string and MessageHandler callback. It looks in the current list of
// routes to see if there is already a matching Route. If there is it replaces the current
// callback with the new one. If not it add a new entry to the list of Routes.
func (r *router) addRoute(topic string, callback MessageHandler) {
r.Lock()
defer r.Unlock()
for e := r.routes.Front(); e != nil; e = e.Next() {
if e.Value.(*route).match(topic) {
r := e.Value.(*route)
r.callback = callback
return
}
}
r.routes.PushBack(&route{topic: topic, callback: callback})
}
// deleteRoute takes a route string, looks for a matching Route in the list of Routes. If
// found it removes the Route from the list.
func (r *router) deleteRoute(topic string) {
r.Lock()
defer r.Unlock()
for e := r.routes.Front(); e != nil; e = e.Next() {
if e.Value.(*route).match(topic) {
r.routes.Remove(e)
return
}
}
}
// setDefaultHandler assigns a default callback that will be called if no matching Route
// is found for an incoming Publish.
func (r *router) setDefaultHandler(handler MessageHandler) {
r.defaultHandler = handler
}
// matchAndDispatch takes a channel of Message pointers as input and starts a go routine that
// takes messages off the channel, matches them against the internal route list and calls the
// associated callback (or the defaultHandler, if one exists and no other route matched). If
// anything is sent down the stop channel the function will end.
func (r *router) matchAndDispatch(messages <-chan *Message, order bool, client *MqttClient) {
go func() {
for {
select {
case message := <-messages:
sent := false
r.RLock()
for e := r.routes.Front(); e != nil; e = e.Next() {
if e.Value.(*route).match(message.Topic()) {
if order {
r.RUnlock()
e.Value.(*route).callback(client, *message)
r.RLock()
} else {
go e.Value.(*route).callback(client, *message)
}
sent = true
}
}
r.RUnlock()
if !sent {
if order {
r.RLock()
r.defaultHandler(client, *message)
r.RUnlock()
} else {
go r.defaultHandler(client, *message)
}
}
case <-r.stop:
return
}
}
}()
}