/
proxy.go
269 lines (221 loc) · 5.56 KB
/
proxy.go
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package main
import (
"fmt"
"log"
"net/http"
"flag"
"sync"
"time"
"go/build"
"os"
"code.google.com/p/go.net/websocket"
)
const basePkg = "github.com/chlu/webcamproxy"
// --------------------------
const MessageBufferSize = 1024
type Message []byte
type MessageSource interface {
Initialize() error
ReadMessage() (Message, error)
}
type Client struct {
queue chan *Message
}
func NewClient() *Client {
queue := make(chan *Message, MessageBufferSize)
return &Client{queue}
}
// --------------------------
const MaxInstacamFrameLength = 20000
const ClientWriteTimeout = 3
const SourceReadTimeout = 1
type InstacamMessageSource struct {
// "ws://1.2.3.4:80/ws"
Url string
camConn *websocket.Conn
}
func (s *InstacamMessageSource) Initialize() error {
if ws, err := websocket.Dial(s.Url, "", "http://localhost/"); err != nil {
return fmt.Errorf("Error initializing Instacam stream: %v", err)
} else {
s.camConn = ws
}
return nil
}
func (s *InstacamMessageSource) ReadMessage() (Message, error) {
msg := make([]byte, MaxInstacamFrameLength)
s.camConn.SetReadDeadline(time.Now().Add(SourceReadTimeout * time.Second))
if n, err := s.camConn.Read(msg); err != nil {
return nil, err
} else {
if n == MaxInstacamFrameLength {
return nil, fmt.Errorf("Frame size exceeded buffer (%d bytes)", MaxInstacamFrameLength)
} else {
return Message(msg[:n]), nil
}
}
return nil, nil
}
// --------------------------
var webcamAddress = flag.String("webcam", "", "IP address of the webcam")
var address = flag.String("address", ":8080", "Address for the proxy to listen")
var verbose = flag.Bool("verbose", false, "Output debug messages")
var src MessageSource
var headerMessage *Message
// Map of clients by id to a channel of messages
var clients map[*Client]chan *Message
var clientsMu sync.RWMutex
// Quit channel for the readMessages goroutine
var quitReading chan bool
var registerClient chan *Client
var unregisterClient chan *Client
// --------------------------
// Write received messages from a channel to the websocket client
func FrameServer(conn *websocket.Conn) {
// Set the PayloadType to binary
conn.PayloadType = websocket.BinaryFrame
client := NewClient()
registerClient <- client
defer func() {
unregisterClient <- client
}()
// Write the header as the first message to the client (MPEG size etc.)
conn.SetWriteDeadline(time.Now().Add(ClientWriteTimeout * time.Second))
if _, err := conn.Write(*headerMessage); err != nil {
return
}
// Continuously read messages from the queue and write to the client, stop on error
for msg := range client.queue {
conn.SetWriteDeadline(time.Now().Add(ClientWriteTimeout * time.Second))
if _, err := conn.Write(*msg); err != nil {
return
}
}
}
func clientRegistration() {
clients = make(map[*Client]chan *Message)
quitReading = make(chan bool)
registerClient = make(chan *Client)
unregisterClient = make(chan *Client)
for {
select {
case client := <-registerClient:
addClient(client)
case client := <-unregisterClient:
removeClient(client)
}
}
}
func addClient(client *Client) {
clientsMu.Lock()
clients[client] = client.queue
clientsMu.Unlock()
// If we added the first client, start reading of messages
if len(clients) == 1 {
go readMessages()
}
if *verbose {
log.Printf("Client connected, %d clients total", len(clients))
}
}
func removeClient(client *Client) {
clientsMu.Lock()
delete(clients, client)
clientsMu.Unlock()
if len(clients) == 0 {
quitReading <- true
}
if *verbose {
log.Printf("Client disconnected, %d clients total", len(clients))
}
}
func readMessages() {
if *verbose {
log.Printf("Start reading messages")
}
for {
select {
case <-quitReading:
if *verbose {
log.Printf("Stop reading messages")
}
return
default:
if msg, err := src.ReadMessage(); err != nil {
if *verbose {
log.Printf("Error reading message from source: %v", err)
log.Printf("Reconnecting...")
}
reconnectSource()
} else {
clientsMu.RLock()
for _, queue := range clients {
select {
case queue <- &msg:
// No op
default:
if *verbose {
log.Printf("Message not sent to client, blocked or closed?")
}
}
}
clientsMu.RUnlock()
}
}
}
}
func readHeaderMessage() error {
if msg, err := src.ReadMessage(); err != nil {
return err
} else {
headerMessage = &msg
}
return nil
}
func reconnectSource() {
for {
if err := src.Initialize(); err != nil {
if *verbose {
log.Printf("Error connecting to source: %v", err)
}
} else {
if *verbose {
log.Printf("Re-connected to source")
}
return
}
time.Sleep(5 * time.Second)
}
}
// --------------------------
// Find the package resource root to serve static files
func getResourceRoot() string {
p, err := build.Default.Import(basePkg, "", build.FindOnly)
if err != nil {
log.Fatalf("Couldn't find resource files: %v", err)
}
return p.Dir
}
func main() {
flag.Parse()
if *webcamAddress == "" {
flag.Usage()
os.Exit(0)
}
websocketUrl := "ws://" + *webcamAddress + ":80/ws"
src = &InstacamMessageSource{Url: websocketUrl}
if err := src.Initialize(); err != nil {
log.Fatalf("Error initializing source: %v", err)
} else {
if *verbose {
log.Printf("Connected to source %s", websocketUrl)
}
}
if err := readHeaderMessage(); err != nil {
log.Fatalf("Error reading header message from source: %v", err)
}
go clientRegistration()
http.Handle("/ws", websocket.Handler(FrameServer))
http.Handle("/", http.FileServer(http.Dir(getResourceRoot()+"/resources/")))
http.ListenAndServe(*address, nil)
}