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server.go
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server.go
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// HTTP server stuff
// return individual jpeg or mime/multipart stream of them that is http MJPEG
package main
import (
"fmt"
"mime/multipart"
"net/http"
"net/textproto"
"strconv"
"sync"
"time"
)
type jpegt struct {
blob []byte
when time.Time
next *jpegt
prev *jpegt
}
type jpegServer struct {
incoming <-chan []byte
l sync.Mutex
cond *sync.Cond
newest *jpegt
oldest *jpegt
count int
tlen int
free *jpegt
maxcount int
maxlen int
}
// run thread
func (js *jpegServer) reader(wg *sync.WaitGroup) {
// init stuff
if js.maxcount == 0 {
js.maxcount = 10 * 10
}
if js.maxlen == 0 {
js.maxlen = 20000000
}
js.cond = sync.NewCond(&js.l)
if wg != nil {
defer wg.Done()
}
for blob := range js.incoming {
js.push(blob)
}
}
func (js *jpegServer) push(blob []byte) {
now := time.Now()
js.l.Lock()
defer js.l.Unlock()
rec := js.free
if rec == nil {
rec = new(jpegt)
} else {
js.free = rec.next
}
rec.blob = blob
rec.when = now
rec.next = nil
rec.prev = js.newest
if js.newest != nil {
js.newest.next = rec
}
js.newest = rec
if js.oldest == nil {
js.oldest = rec
}
js.count++
js.tlen += len(blob)
for (js.count > js.maxcount) || (js.tlen > js.maxlen) {
if js.oldest == js.newest {
// keep at least 1
break
}
xrec := js.oldest
js.oldest = xrec.next
js.oldest.prev = nil
xrec.next = js.free
js.tlen -= len(xrec.blob)
js.count--
xrec.blob = nil
xrec.prev = nil
js.free = xrec
}
js.cond.Broadcast()
}
func (js *jpegServer) getNewest() []byte {
js.l.Lock()
defer js.l.Unlock()
if js.newest == nil {
return nil
}
return js.newest.blob
}
// return a copy of newest jpegt
// copy works around some threading mess
func (js *jpegServer) getNewestJT() (blob []byte, when time.Time) {
js.l.Lock()
defer js.l.Unlock()
if js.newest == nil {
blob = nil
return
}
blob = js.newest.blob
when = js.newest.when
return
}
func (js *jpegServer) getAfterJT(then time.Time) (blob []byte, when time.Time) {
js.l.Lock()
defer js.l.Unlock()
cur := js.oldest
for cur != nil {
if cur.when.After(then) {
blob = cur.blob
when = cur.when
return
}
cur = cur.next
}
blob = nil
return
}
func (js *jpegServer) waitAfterJT(then time.Time) (blob []byte, when time.Time) {
js.l.Lock()
defer js.l.Unlock()
cur := js.oldest
for cur != nil {
if cur.when.After(then) {
blob = cur.blob
when = cur.when
return
}
cur = cur.next
}
for {
js.cond.Wait()
if js.newest != nil && js.newest.when.After(then) {
blob = js.newest.blob
when = js.newest.when
return
}
}
}
func formInt(request *http.Request, name string, defaultValue, min, max int) int {
sv := request.FormValue(name)
if sv == "" {
return defaultValue
}
v, err := strconv.ParseInt(sv, 0, 64)
if err != nil {
return defaultValue
}
i := int(v)
if i < min {
return min
}
if i > max {
return max
}
return i
}
func (js *jpegServer) ServeHTTP(out http.ResponseWriter, request *http.Request) {
path := request.URL.Path
if path == "/jpeg" {
out.Header().Set("Content-Type", "image/jpeg")
out.Write(js.getNewest())
return
}
if path == "/" {
http.Redirect(out, request, "/mjpeg", http.StatusFound)
return
}
request.ParseForm()
fps := formInt(request, "fps", 15, 1, 30)
offset := formInt(request, "start", 0, -100, 0)
period := time.Second / time.Duration(fps)
startTime := time.Now()
nextFrame := startTime.Add(period)
caughtUp := true
var blob []byte
var when time.Time
if offset < 0 {
startTime = startTime.Add(time.Duration(offset) * time.Second)
blob, when = js.getAfterJT(startTime)
caughtUp = (blob == nil)
}
m := multipart.NewWriter(out)
defer m.Close()
out.Header().Set("Content-Type", "multipart/x-mixed-replace; boundary="+m.Boundary())
out.Header().Set("Connection", "close")
h := textproto.MIMEHeader{}
st := fmt.Sprint(startTime.Unix())
for {
if blob == nil {
blob, when = js.getNewestJT()
} else {
if !caughtUp {
nb, nw := js.getAfterJT(when)
if nb == nil {
caughtUp = true
} else {
blob = nb
when = nw
}
}
if caughtUp {
blob, when = js.waitAfterJT(nextFrame)
nextFrame = when
}
}
if blob == nil {
// TODO: log error?
break
}
h.Set("Content-Type", "image/jpeg")
h.Set("Content-Length", fmt.Sprint(len(blob)))
h.Set("X-StartTime", st)
h.Set("X-TimeStamp", fmt.Sprint(when.Unix()))
mw, err := m.CreatePart(h)
if err != nil {
break
}
_, err = mw.Write(blob)
if err != nil {
break
}
if flusher, ok := mw.(http.Flusher); ok {
flusher.Flush()
}
now := time.Now()
if now.Before(nextFrame) {
time.Sleep(nextFrame.Sub(now))
}
nextFrame = nextFrame.Add(period)
}
}