/
compression.go
162 lines (138 loc) · 4.39 KB
/
compression.go
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// Copyright 2016 The Mellium Contributors.
// Use of this source code is governed by the BSD 2-clause
// license that can be found in the LICENSE file.
// Package compress implements XEP-0138: Stream Compression and XEP-0229: Stream
// Compression with LZW.
package compress // import "mellium.im/xmpp/compress"
import (
"context"
"encoding/xml"
"errors"
"fmt"
"io"
"mellium.im/xmlstream"
"mellium.im/xmpp"
"mellium.im/xmpp/stream"
)
// Namespaces used by stream compression.
const (
NSFeatures = "http://jabber.org/features/compress"
NSProtocol = "http://jabber.org/protocol/compress"
)
var (
errNoMethods = errors.New("No supported compression methods were found")
)
// New returns a new xmpp.StreamFeature that can be used to negotiate stream
// compression.
// The returned stream feature always supports ZLIB compression; other
// compression methods are optional.
func New(methods ...Method) xmpp.StreamFeature {
// TODO: Throw them into a map to dedup and then iterate over that?
methods = append(methods, zlibMethod)
return xmpp.StreamFeature{
Name: xml.Name{Local: "compression", Space: NSFeatures},
Necessary: xmpp.Secure | xmpp.Authn,
List: func(ctx context.Context, e xmlstream.TokenWriter, start xml.StartElement) (req bool, err error) {
if err = e.EncodeToken(start); err != nil {
return req, err
}
methodStart := xml.StartElement{Name: xml.Name{Local: "method"}}
for _, m := range methods {
select {
case <-ctx.Done():
return req, ctx.Err()
default:
}
if err = e.EncodeToken(methodStart); err != nil {
return req, err
}
if err = e.EncodeToken(xml.CharData(m.Name)); err != nil {
return req, err
}
if err = e.EncodeToken(methodStart.End()); err != nil {
return req, err
}
}
return req, e.EncodeToken(start.End())
},
Parse: func(ctx context.Context, r xml.TokenReader, start *xml.StartElement) (bool, interface{}, error) {
listed := struct {
XMLName xml.Name `xml:"http://jabber.org/features/compress compression"`
Methods []string `xml:"http://jabber.org/features/compress method"`
}{}
if err := xml.NewTokenDecoder(r).DecodeElement(&listed, start); err != nil {
return false, nil, err
}
if len(listed.Methods) == 0 {
return false, nil, errNoMethods
}
return true, listed.Methods, nil
},
Negotiate: func(ctx context.Context, session *xmpp.Session, data interface{}) (mask xmpp.SessionState, rw io.ReadWriter, err error) {
conn := session.Conn()
d := xml.NewTokenDecoder(session)
// If we're a server.
if (session.State() & xmpp.Received) == xmpp.Received {
clientSelected := struct {
XMLName xml.Name `xml:"http://jabber.org/protocol/compress compress"`
Method string `xml:"method"`
}{}
if err = d.Decode(&clientSelected); err != nil {
return
}
// If no method was selected, or something weird happened with decoding…
if clientSelected.Method == "" {
_, err = fmt.Fprint(conn, `<failure xmlns='`+NSProtocol+`'><setup-failed/></failure>`)
return
}
var selected Method
for _, method := range methods {
if method.Name == clientSelected.Method {
selected = method
break
}
}
// The client requested a method that we did not send…
if selected.Name == "" {
_, err = fmt.Fprint(conn, `<failure xmlns='`+NSProtocol+`'><unsupported-method/></failure>`)
return
}
if _, err = fmt.Fprint(conn, `<compressed xmlns='`+NSProtocol+`'/>`); err != nil {
return
}
rw, err = selected.Wrapper(conn)
return mask, rw, err
}
var selected Method
selectmethod:
for _, m := range methods {
for _, name := range data.([]string) {
if name == m.Name {
selected = m
break selectmethod
}
}
}
if selected.Name == "" {
return mask, nil, errors.New(`No matching compression method found`)
}
_, err = fmt.Fprintf(conn, `<compress xmlns='`+NSProtocol+`'><method>%s</method></compress>`, selected.Name)
if err != nil {
return
}
tok, err := d.Token()
if err != nil {
return mask, nil, err
}
if t, ok := tok.(xml.StartElement); ok && t.Name.Local == "compressed" && t.Name.Space == NSProtocol {
if err = d.Skip(); err != nil {
return mask, nil, err
}
rw, err = selected.Wrapper(conn)
return mask, rw, err
}
// TODO: Use appropriate errors.
return mask, nil, stream.BadFormat
},
}
}