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multistream.go
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multistream.go
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// Package multistream implements a simple stream router for the
// multistream-select protocoli. The protocol is defined at
// https://github.com/multiformats/multistream-select
package multistream
import (
"bufio"
"bytes"
"errors"
"fmt"
"io"
"sync"
"github.com/multiformats/go-varint"
)
// ErrTooLarge is an error to signal that an incoming message was too large
var ErrTooLarge = errors.New("incoming message was too large")
// ProtocolID identifies the multistream protocol itself and makes sure
// the multistream muxers on both sides of a channel can work with each other.
const ProtocolID = "/multistream/1.0.0"
var writerPool = sync.Pool{
New: func() interface{} {
return bufio.NewWriter(nil)
},
}
// HandlerFunc is a user-provided function used by the MultistreamMuxer to
// handle a protocol/stream.
type HandlerFunc = func(protocol string, rwc io.ReadWriteCloser) error
// Handler is a wrapper to HandlerFunc which attaches a name (protocol) and a
// match function which can optionally be used to select a handler by other
// means than the name.
type Handler struct {
MatchFunc func(string) bool
Handle HandlerFunc
AddName string
}
// MultistreamMuxer is a muxer for multistream. Depending on the stream
// protocol tag it will select the right handler and hand the stream off to it.
type MultistreamMuxer struct {
handlerlock sync.RWMutex
handlers []Handler
}
// NewMultistreamMuxer creates a muxer.
func NewMultistreamMuxer() *MultistreamMuxer {
return new(MultistreamMuxer)
}
// LazyConn is the connection type returned by the lazy negotiation functions.
type LazyConn interface {
io.ReadWriteCloser
// Flush flushes the lazy negotiation, if any.
Flush() error
}
func writeUvarint(w io.Writer, i uint64) error {
varintbuf := make([]byte, 16)
n := varint.PutUvarint(varintbuf, i)
_, err := w.Write(varintbuf[:n])
if err != nil {
return err
}
return nil
}
func delimWriteBuffered(w io.Writer, mes []byte) error {
bw := getWriter(w)
defer putWriter(bw)
err := delimWrite(bw, mes)
if err != nil {
return err
}
return bw.Flush()
}
func delitmWriteAll(w io.Writer, messages ...[]byte) error {
for _, mes := range messages {
if err := delimWrite(w, mes); err != nil {
return fmt.Errorf("failed to write messages %s, err: %v ", string(mes), err)
}
}
return nil
}
func delimWrite(w io.Writer, mes []byte) error {
err := writeUvarint(w, uint64(len(mes)+1))
if err != nil {
return err
}
_, err = w.Write(mes)
if err != nil {
return err
}
_, err = w.Write([]byte{'\n'})
if err != nil {
return err
}
return nil
}
// Ls is a Multistream muxer command which returns the list of handler names
// available on a muxer.
func Ls(rw io.ReadWriter) ([]string, error) {
err := handshake(rw)
if err != nil {
return nil, err
}
err = delimWriteBuffered(rw, []byte("ls"))
if err != nil {
return nil, err
}
response, err := lpReadBuf(rw)
if err != nil {
return nil, err
}
r := bytes.NewReader(response)
var out []string
for {
val, err := lpReadBuf(r)
switch err {
default:
return nil, err
case io.EOF:
return out, nil
case nil:
out = append(out, string(val))
}
}
}
func fulltextMatch(s string) func(string) bool {
return func(a string) bool {
return a == s
}
}
// AddHandler attaches a new protocol handler to the muxer.
func (msm *MultistreamMuxer) AddHandler(protocol string, handler HandlerFunc) {
msm.AddHandlerWithFunc(protocol, fulltextMatch(protocol), handler)
}
// AddHandlerWithFunc attaches a new protocol handler to the muxer with a match.
// If the match function returns true for a given protocol tag, the protocol
// will be selected even if the handler name and protocol tags are different.
func (msm *MultistreamMuxer) AddHandlerWithFunc(protocol string, match func(string) bool, handler HandlerFunc) {
msm.handlerlock.Lock()
defer msm.handlerlock.Unlock()
msm.removeHandler(protocol)
msm.handlers = append(msm.handlers, Handler{
MatchFunc: match,
Handle: handler,
AddName: protocol,
})
}
// RemoveHandler removes the handler with the given name from the muxer.
func (msm *MultistreamMuxer) RemoveHandler(protocol string) {
msm.handlerlock.Lock()
defer msm.handlerlock.Unlock()
msm.removeHandler(protocol)
}
func (msm *MultistreamMuxer) removeHandler(protocol string) {
for i, h := range msm.handlers {
if h.AddName == protocol {
msm.handlers = append(msm.handlers[:i], msm.handlers[i+1:]...)
return
}
}
}
// Protocols returns the list of handler-names added to this this muxer.
func (msm *MultistreamMuxer) Protocols() []string {
msm.handlerlock.RLock()
defer msm.handlerlock.RUnlock()
var out []string
for _, h := range msm.handlers {
out = append(out, h.AddName)
}
return out
}
// ErrIncorrectVersion is an error reported when the muxer protocol negotiation
// fails because of a ProtocolID mismatch.
var ErrIncorrectVersion = errors.New("client connected with incorrect version")
func (msm *MultistreamMuxer) findHandler(proto string) *Handler {
msm.handlerlock.RLock()
defer msm.handlerlock.RUnlock()
for _, h := range msm.handlers {
if h.MatchFunc(proto) {
return &h
}
}
return nil
}
// NegotiateLazy performs protocol selection and returns
// a multistream, the protocol used, the handler and an error. It is lazy
// because the write-handshake is performed on a subroutine, allowing this
// to return before that handshake is completed.
func (msm *MultistreamMuxer) NegotiateLazy(rwc io.ReadWriteCloser) (io.ReadWriteCloser, string, HandlerFunc, error) {
pval := make(chan string, 1)
writeErr := make(chan error, 1)
defer close(pval)
lzc := &lazyServerConn{
con: rwc,
}
started := make(chan struct{})
go lzc.waitForHandshake.Do(func() {
close(started)
defer close(writeErr)
if err := delimWriteBuffered(rwc, []byte(ProtocolID)); err != nil {
lzc.werr = err
writeErr <- err
return
}
for proto := range pval {
if err := delimWriteBuffered(rwc, []byte(proto)); err != nil {
lzc.werr = err
writeErr <- err
return
}
}
})
<-started
line, err := ReadNextToken(rwc)
if err != nil {
return nil, "", nil, err
}
if line != ProtocolID {
rwc.Close()
return nil, "", nil, ErrIncorrectVersion
}
loop:
for {
// Now read and respond to commands until they send a valid protocol id
tok, err := ReadNextToken(rwc)
if err != nil {
rwc.Close()
return nil, "", nil, err
}
switch tok {
case "ls":
protos, err := msm.encodeLocalProtocols()
if err != nil {
rwc.Close()
return nil, "", nil, err
}
select {
case pval <- string(protos):
case err := <-writeErr:
rwc.Close()
return nil, "", nil, err
}
default:
h := msm.findHandler(tok)
if h == nil {
select {
case pval <- "na":
case err := <-writeErr:
rwc.Close()
return nil, "", nil, err
}
continue loop
}
select {
case pval <- tok:
case <-writeErr:
// explicitly ignore this error. It will be returned to any
// writers and if we don't plan on writing anything, we still
// want to complete the handshake
}
// hand off processing to the sub-protocol handler
return lzc, tok, h.Handle, nil
}
}
}
// Negotiate performs protocol selection and returns the protocol name and
// the matching handler function for it (or an error).
func (msm *MultistreamMuxer) Negotiate(rwc io.ReadWriteCloser) (string, HandlerFunc, error) {
// Send our protocol ID
err := delimWriteBuffered(rwc, []byte(ProtocolID))
if err != nil {
return "", nil, err
}
line, err := ReadNextToken(rwc)
if err != nil {
return "", nil, err
}
if line != ProtocolID {
rwc.Close()
return "", nil, ErrIncorrectVersion
}
loop:
for {
// Now read and respond to commands until they send a valid protocol id
tok, err := ReadNextToken(rwc)
if err != nil {
return "", nil, err
}
switch tok {
case "ls":
err := msm.Ls(rwc)
if err != nil {
return "", nil, err
}
default:
h := msm.findHandler(tok)
if h == nil {
err := delimWriteBuffered(rwc, []byte("na"))
if err != nil {
return "", nil, err
}
continue loop
}
err := delimWriteBuffered(rwc, []byte(tok))
if err != nil {
return "", nil, err
}
// hand off processing to the sub-protocol handler
return tok, h.Handle, nil
}
}
}
// Ls implements the "ls" command which writes the list of
// supported protocols to the given Writer.
func (msm *MultistreamMuxer) Ls(w io.Writer) error {
protos, err := msm.encodeLocalProtocols()
if err != nil {
return err
}
return delimWrite(w, protos)
}
// encodeLocalProtocols encodes the protocols this multistream-select router
// handles, packed in a list of varint-delimited strings.
func (msm *MultistreamMuxer) encodeLocalProtocols() ([]byte, error) {
buf := new(bytes.Buffer)
msm.handlerlock.RLock()
for _, h := range msm.handlers {
err := delimWrite(buf, []byte(h.AddName))
if err != nil {
msm.handlerlock.RUnlock()
return nil, err
}
}
msm.handlerlock.RUnlock()
return buf.Bytes(), nil
}
// Handle performs protocol negotiation on a ReadWriteCloser
// (i.e. a connection). It will find a matching handler for the
// incoming protocol and pass the ReadWriteCloser to it.
func (msm *MultistreamMuxer) Handle(rwc io.ReadWriteCloser) error {
p, h, err := msm.Negotiate(rwc)
if err != nil {
return err
}
return h(p, rwc)
}
// ReadNextToken extracts a token from a Reader. It is used during
// protocol negotiation and returns a string.
func ReadNextToken(r io.Reader) (string, error) {
tok, err := ReadNextTokenBytes(r)
if err != nil {
return "", err
}
return string(tok), nil
}
// ReadNextTokenBytes extracts a token from a Reader. It is used
// during protocol negotiation and returns a byte slice.
func ReadNextTokenBytes(r io.Reader) ([]byte, error) {
data, err := lpReadBuf(r)
switch err {
case nil:
return data, nil
case ErrTooLarge:
return nil, ErrTooLarge
default:
return nil, err
}
}
func lpReadBuf(r io.Reader) ([]byte, error) {
br, ok := r.(io.ByteReader)
if !ok {
br = &byteReader{r}
}
length, err := varint.ReadUvarint(br)
if err != nil {
return nil, err
}
if length > 64*1024 {
return nil, ErrTooLarge
}
buf := make([]byte, length)
_, err = io.ReadFull(r, buf)
if err != nil {
if err == io.EOF {
err = io.ErrUnexpectedEOF
}
return nil, err
}
if len(buf) == 0 || buf[length-1] != '\n' {
return nil, errors.New("message did not have trailing newline")
}
// slice off the trailing newline
buf = buf[:length-1]
return buf, nil
}
// byteReader implements the ByteReader interface that ReadUVarint requires
type byteReader struct {
io.Reader
}
func (br *byteReader) ReadByte() (byte, error) {
var b [1]byte
n, err := br.Read(b[:])
if n == 1 {
return b[0], nil
}
if err == nil {
if n != 0 {
panic("read more bytes than buffer size")
}
err = io.ErrNoProgress
}
return 0, err
}
func getWriter(w io.Writer) *bufio.Writer {
bw := writerPool.Get().(*bufio.Writer)
bw.Reset(w)
return bw
}
func putWriter(bw *bufio.Writer) {
bw.Reset(nil)
writerPool.Put(bw)
}