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// Copyright (C) 2019-2024 Algorand, Inc.
// This file is part of go-algorand
//
// go-algorand 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.
//
// go-algorand 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.
//
// You should have received a copy of the GNU Affero General Public License
// along with go-algorand. If not, see <https://www.gnu.org/licenses/>.
package network
import (
"fmt"
"sync/atomic"
)
// Multiplexer is a message handler that sorts incoming messages by Tag and passes
// them along to the relevant message handler for that type of message.
type Multiplexer struct {
msgHandlers atomic.Value // stores map[Tag]MessageHandler, an immutable map.
}
// MakeMultiplexer creates an empty Multiplexer
func MakeMultiplexer() *Multiplexer {
m := &Multiplexer{}
m.ClearHandlers([]Tag{}) // allocate the map
return m
}
// getHandlersMap retrieves the handlers map.
func (m *Multiplexer) getHandlersMap() map[Tag]MessageHandler {
handlersVal := m.msgHandlers.Load()
if handlers, valid := handlersVal.(map[Tag]MessageHandler); valid {
return handlers
}
return nil
}
// Retrives the handler for the given message Tag from the handlers array while taking a read lock.
func (m *Multiplexer) getHandler(tag Tag) (MessageHandler, bool) {
if handlers := m.getHandlersMap(); handlers != nil {
handler, ok := handlers[tag]
return handler, ok
}
return nil, false
}
// Handle is the "input" side of the multiplexer. It dispatches the message to the previously defined handler.
func (m *Multiplexer) Handle(msg IncomingMessage) OutgoingMessage {
handler, ok := m.getHandler(msg.Tag)
if ok {
outmsg := handler.Handle(msg)
return outmsg
}
return OutgoingMessage{}
}
// RegisterHandlers registers the set of given message handlers.
func (m *Multiplexer) RegisterHandlers(dispatch []TaggedMessageHandler) {
mp := make(map[Tag]MessageHandler)
if existingMap := m.getHandlersMap(); existingMap != nil {
for k, v := range existingMap {
mp[k] = v
}
}
for _, v := range dispatch {
if _, has := mp[v.Tag]; has {
panic(fmt.Sprintf("Already registered a handler for tag %v", v.Tag))
}
mp[v.Tag] = v.MessageHandler
}
m.msgHandlers.Store(mp)
}
// ClearHandlers deregisters all the existing message handlers other than the one provided in the excludeTags list
func (m *Multiplexer) ClearHandlers(excludeTags []Tag) {
if len(excludeTags) == 0 {
m.msgHandlers.Store(make(map[Tag]MessageHandler))
return
}
// convert into map, so that we can exclude duplicates.
excludeTagsMap := make(map[Tag]bool)
for _, tag := range excludeTags {
excludeTagsMap[tag] = true
}
currentHandlersMap := m.getHandlersMap()
newMap := make(map[Tag]MessageHandler, len(excludeTagsMap))
for tag, handler := range currentHandlersMap {
if excludeTagsMap[tag] {
newMap[tag] = handler
}
}
m.msgHandlers.Store(newMap)
}
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