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subscriber.go
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subscriber.go
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package zanarkand
import (
"bufio"
"bytes"
"compress/zlib"
"fmt"
)
// Subscriber describes the interface for individual Frame segment subscribers.
type Subscriber interface {
Subscribe(*Sniffer)
Close()
}
// GameEventSubscriber is a Subscriber for GameEvent segments.
type GameEventSubscriber struct {
IngressEvents chan *GameEventMessage
EgressEvents chan *GameEventMessage
}
// NewGameEventSubscriber returns a Subscriber handle with channels for inbound and outbound GameEventMessages.
func NewGameEventSubscriber() *GameEventSubscriber {
return &GameEventSubscriber{
IngressEvents: make(chan *GameEventMessage),
EgressEvents: make(chan *GameEventMessage),
}
}
// Subscribe starts the GameEventSubscriber.
func (g *GameEventSubscriber) Subscribe(s *Sniffer) error {
if !s.Active {
go s.Start()
}
for {
frame, err := s.NextFrame()
if err != nil {
return fmt.Errorf("error retrieving next frame: %w", err)
}
// Setup our Message reader
r := bufio.NewReader(bytes.NewReader(frame.Body))
if frame.Compressed {
z, err := zlib.NewReader(bytes.NewReader(frame.Body))
if err != nil {
return fmt.Errorf("error creating ZLIB decoder: %w", err)
}
defer z.Close()
r.Reset(z)
}
for i := 0; i < int(frame.Count); i++ {
header := new(GenericHeader)
err := header.Decode(r)
if err != nil {
return ErrDecodingFailure{Err: err}
}
if header.Segment == GameEvent {
msg := new(GameEventMessage)
msg.Decode(r)
switch frame.Direction() {
case FrameIngress:
g.IngressEvents <- msg
case FrameEgress:
g.EgressEvents <- msg
default:
return ErrDecodingFailure{Err: fmt.Errorf("unexpected frame direction")}
}
}
}
// We're done with the current frame,
// if Sniffer is stopped then exit and
// user can start a new subscriber routine.
if !s.Active {
return nil
}
}
}
// Close will stop a sniffer, drain the channels, then close the channels.
func (g *GameEventSubscriber) Close(s *Sniffer) {
s.Stop()
close(g.IngressEvents)
close(g.EgressEvents)
}
// KeepaliveSubscriber is a Subscriber for Keepalive segments.
type KeepaliveSubscriber struct {
Events chan *KeepaliveMessage
}
// NewKeepaliveSubscriber returns a Subscriber handle. As the traffic is minimal, this subscriber uses a single Event channel.
func NewKeepaliveSubscriber() *KeepaliveSubscriber {
return &KeepaliveSubscriber{
Events: make(chan *KeepaliveMessage),
}
}
// Subscribe starts the KeepaliveSubscriber.
func (k *KeepaliveSubscriber) Subscribe(s *Sniffer) error {
if !s.Active {
go s.Start()
}
for {
frame, err := s.NextFrame()
if err != nil {
return fmt.Errorf("error retrieving next frame: %s", err)
}
// Setup our Message reader
r := bufio.NewReader(bytes.NewReader(frame.Body))
if frame.Compressed {
z, err := zlib.NewReader(bytes.NewReader(frame.Body))
if err != nil {
return fmt.Errorf("error creating ZLIB decoder: %w", err)
}
defer z.Close()
r.Reset(z)
}
for i := 0; i < int(frame.Count); i++ {
header := new(GenericHeader)
err := header.Decode(r)
if err != nil {
return ErrDecodingFailure{Err: err}
}
if header.Segment == ServerPing || header.Segment == ServerPong {
msg := new(KeepaliveMessage)
msg.Decode(r)
k.Events <- msg
}
}
if !s.Active {
return nil
}
}
}
// Close will stop a sniffer, drain the channel, then close the channel.
func (k *KeepaliveSubscriber) Close(s *Sniffer) {
s.Stop()
close(k.Events)
}