robocar-tools/vendor/github.com/eclipse/paho.mqtt.golang/router.go

230 lines
7.1 KiB
Go

/*
* 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"
"github.com/eclipse/paho.mqtt.golang/packets"
)
// 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 {
return len(topic) == 0
}
if len(topic) == 0 {
return route[0] == "#"
}
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(routeSplit(route), strings.Split(topic, "/"))
}
// removes $share and sharename when splitting the route to allow
// shared subscription routes to correctly match the topic
func routeSplit(route string) []string {
var result []string
if strings.HasPrefix(route, "$share") {
result = strings.Split(route, "/")[2:]
} else {
result = strings.Split(route, "/")
}
return result
}
// 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 *packets.PublishPacket
}
// newRouter returns a new instance of a Router and channel which can be used to tell the Router
// to stop
func newRouter() *router {
router := &router{routes: list.New(), messages: make(chan *packets.PublishPacket)}
return router
}
// 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).topic == 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).topic == 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.Lock()
defer r.Unlock()
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 *packets.PublishPacket, order bool, client *client) <-chan *PacketAndToken {
var wg sync.WaitGroup
ackOutChan := make(chan *PacketAndToken) // Channel returned to caller; closed when messages channel closed
var ackInChan chan *PacketAndToken // ACKs generated by ackFunc get put onto this channel
stopAckCopy := make(chan struct{}) // Closure requests stop of go routine copying ackInChan to ackOutChan
ackCopyStopped := make(chan struct{}) // Closure indicates that it is safe to close ackOutChan
goRoutinesDone := make(chan struct{}) // closed on wg.Done()
if order {
ackInChan = ackOutChan // When order = true no go routines are used so safe to use one channel and close when done
} else {
// When order = false ACK messages are sent in go routines so ackInChan cannot be closed until all goroutines done
ackInChan = make(chan *PacketAndToken)
go func() { // go routine to copy from ackInChan to ackOutChan until stopped
for {
select {
case a := <-ackInChan:
ackOutChan <- a
case <-stopAckCopy:
close(ackCopyStopped) // Signal main go routine that it is safe to close ackOutChan
for {
select {
case <-ackInChan: // drain ackInChan to ensure all goRoutines can complete cleanly (ACK dropped)
DEBUG.Println(ROU, "matchAndDispatch received acknowledgment after processing stopped (ACK dropped).")
case <-goRoutinesDone:
close(ackInChan) // Nothing further should be sent (a panic is probably better than silent failure)
DEBUG.Println(ROU, "matchAndDispatch order=false copy goroutine exiting.")
return
}
}
}
}
}()
}
go func() { // Main go routine handling inbound messages
for message := range messages {
// DEBUG.Println(ROU, "matchAndDispatch received message")
sent := false
r.RLock()
m := messageFromPublish(message, ackFunc(ackInChan, client.persist, message))
var handlers []MessageHandler
for e := r.routes.Front(); e != nil; e = e.Next() {
if e.Value.(*route).match(message.TopicName) {
if order {
handlers = append(handlers, e.Value.(*route).callback)
} else {
hd := e.Value.(*route).callback
wg.Add(1)
go func() {
hd(client, m)
m.Ack()
wg.Done()
}()
}
sent = true
}
}
if !sent {
if r.defaultHandler != nil {
if order {
handlers = append(handlers, r.defaultHandler)
} else {
wg.Add(1)
go func() {
r.defaultHandler(client, m)
m.Ack()
wg.Done()
}()
}
} else {
DEBUG.Println(ROU, "matchAndDispatch received message and no handler was available. Message will NOT be acknowledged.")
}
}
r.RUnlock()
for _, handler := range handlers {
handler(client, m)
m.Ack()
}
// DEBUG.Println(ROU, "matchAndDispatch handled message")
}
if order {
close(ackOutChan)
} else { // Ensure that nothing further will be written to ackOutChan before closing it
close(stopAckCopy)
<-ackCopyStopped
close(ackOutChan)
go func() {
wg.Wait() // Note: If this remains running then the user has handlers that are not returning
close(goRoutinesDone)
}()
}
DEBUG.Println(ROU, "matchAndDispatch exiting")
}()
return ackOutChan
}