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multiplex.go
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multiplex.go
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package multiplex
import (
"bufio"
"encoding/binary"
"errors"
"fmt"
"io"
"io/ioutil"
"sync"
)
const (
NewStream = iota
Receiver
Initiator
Unknown
Close
)
var _ = ioutil.ReadAll
var _ = bufio.NewReadWriter
var _ = binary.MaxVarintLen16
type msg struct {
header uint64
data []byte
err chan<- error
}
type Stream struct {
id uint64
name string
header uint64
closed chan struct{}
data_in chan []byte
data_out chan<- msg
extra []byte
}
func newStream(id uint64, name string, initiator bool, send chan<- msg) *Stream {
var hfn uint64
if initiator {
hfn = 2
} else {
hfn = 1
}
return &Stream{
id: id,
name: name,
header: (id << 3) | hfn,
data_in: make(chan []byte, 8),
data_out: send,
closed: make(chan struct{}),
}
}
func (s *Stream) Name() string {
return s.name
}
func (s *Stream) receive(b []byte) {
select {
case s.data_in <- b:
case <-s.closed:
}
}
func (m *Multiplex) Accept() (*Stream, error) {
select {
case s, ok := <-m.nstreams:
if !ok {
return nil, errors.New("multiplex closed")
}
return s, nil
case err := <-m.errs:
return nil, err
case <-m.closed:
return nil, errors.New("multiplex closed")
}
}
func (s *Stream) Read(b []byte) (int, error) {
if s.extra == nil {
select {
case <-s.closed:
return 0, io.EOF
case read, ok := <-s.data_in:
if !ok {
return 0, io.EOF
}
s.extra = read
}
}
n := copy(b, s.extra)
if n < len(s.extra) {
s.extra = s.extra[n:]
} else {
s.extra = nil
}
return n, nil
}
func (s *Stream) Write(b []byte) (int, error) {
errs := make(chan error, 1)
select {
case s.data_out <- msg{header: s.header, data: b, err: errs}:
select {
case err := <-errs:
return len(b), err
case <-s.closed:
return 0, errors.New("stream closed")
}
case <-s.closed:
return 0, errors.New("stream closed")
}
}
func (s *Stream) Close() error {
select {
case <-s.closed:
return nil
default:
close(s.closed)
select {
case s.data_out <- msg{
header: (s.id << 3) | Close,
err: make(chan error, 1), //throw away error, whatever
}:
default:
}
close(s.data_in)
return nil
}
}
type Multiplex struct {
con io.ReadWriteCloser
buf *bufio.Reader
nextID uint64
outchan chan msg
closed chan struct{}
initiator bool
nstreams chan *Stream
errs chan error
channels map[uint64]*Stream
ch_lock sync.Mutex
}
func NewMultiplex(con io.ReadWriteCloser, initiator bool) *Multiplex {
mp := &Multiplex{
con: con,
initiator: initiator,
buf: bufio.NewReader(con),
channels: make(map[uint64]*Stream),
outchan: make(chan msg),
closed: make(chan struct{}),
nstreams: make(chan *Stream, 16),
errs: make(chan error),
}
go mp.handleOutgoing()
go mp.handleIncoming()
return mp
}
func (mp *Multiplex) Close() error {
if mp.IsClosed() {
return nil
}
close(mp.closed)
mp.ch_lock.Lock()
defer mp.ch_lock.Unlock()
for _, s := range mp.channels {
err := s.Close()
if err != nil {
return err
}
}
return nil
}
func (mp *Multiplex) IsClosed() bool {
select {
case <-mp.closed:
return true
default:
return false
}
}
func (mp *Multiplex) handleOutgoing() {
for {
select {
case msg, ok := <-mp.outchan:
if !ok {
return
}
buf := EncodeVarint(msg.header)
_, err := mp.con.Write(buf)
if err != nil {
msg.err <- err
continue
}
buf = EncodeVarint(uint64(len(msg.data)))
_, err = mp.con.Write(buf)
if err != nil {
msg.err <- err
continue
}
_, err = mp.con.Write(msg.data)
if err != nil {
msg.err <- err
continue
}
msg.err <- nil
case <-mp.closed:
return
}
}
}
func (mp *Multiplex) nextChanID() (out uint64) {
if mp.initiator {
out = mp.nextID + 1
} else {
out = mp.nextID
}
mp.nextID += 2
return
}
func (mp *Multiplex) NewStream() *Stream {
return mp.NewNamedStream("")
}
func (mp *Multiplex) NewNamedStream(name string) *Stream {
mp.ch_lock.Lock()
sid := mp.nextChanID()
header := (sid << 3) | NewStream
if name == "" {
name = fmt.Sprint(sid)
}
s := newStream(sid, name, true, mp.outchan)
mp.channels[sid] = s
mp.ch_lock.Unlock()
mp.outchan <- msg{
header: header,
data: []byte(name),
err: make(chan error, 1), //throw away error
}
return s
}
func (mp *Multiplex) sendErr(err error) {
select {
case mp.errs <- err:
case <-mp.closed:
}
}
func (mp *Multiplex) handleIncoming() {
defer mp.shutdown()
for {
ch, tag, err := mp.readNextHeader()
if err != nil {
mp.sendErr(err)
return
}
b, err := mp.readNext()
if err != nil {
mp.sendErr(err)
return
}
mp.ch_lock.Lock()
msch, ok := mp.channels[ch]
if !ok {
var name string
if tag == NewStream {
name = string(b)
}
msch = newStream(ch, name, false, mp.outchan)
mp.channels[ch] = msch
select {
case mp.nstreams <- msch:
case <-mp.closed:
return
}
if tag == NewStream {
mp.ch_lock.Unlock()
continue
}
}
mp.ch_lock.Unlock()
if tag == Close {
msch.Close()
mp.ch_lock.Lock()
delete(mp.channels, ch)
mp.ch_lock.Unlock()
continue
}
msch.receive(b)
}
}
func (mp *Multiplex) shutdown() {
mp.ch_lock.Lock()
defer mp.ch_lock.Unlock()
for _, s := range mp.channels {
s.Close()
}
}
func (mp *Multiplex) readNextHeader() (uint64, uint64, error) {
h, _, err := DecodeVarint(mp.buf)
if err != nil {
return 0, 0, err
}
// get channel ID
ch := h >> 3
rem := h & 7
return ch, rem, nil
}
func (mp *Multiplex) readNext() ([]byte, error) {
// get length
l, _, err := DecodeVarint(mp.buf)
if err != nil {
return nil, err
}
buf := make([]byte, l)
n, err := io.ReadFull(mp.buf, buf)
if err != nil {
return nil, err
}
if n != int(l) {
panic("NOT THE SAME")
}
return buf, nil
}
func EncodeVarint(x uint64) []byte {
var buf [10]byte
var n int
for n = 0; x > 127; n++ {
buf[n] = 0x80 | uint8(x&0x7F)
x >>= 7
}
buf[n] = uint8(x)
n++
return buf[0:n]
}
func DecodeVarint(r *bufio.Reader) (x uint64, n int, err error) {
// x, n already 0
for shift := uint(0); shift < 64; shift += 7 {
val, err := r.ReadByte()
if err != nil {
return 0, 0, err
}
b := uint64(val)
n++
x |= (b & 0x7F) << shift
if (b & 0x80) == 0 {
return x, n, nil
}
}
// The number is too large to represent in a 64-bit value.
return 0, 0, errors.New("Too large of a number!")
}