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// Copyright 2014 The Go Authors. All rights reserved.
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.
// See https://code.google.com/p/go/source/browse/CONTRIBUTORS
// Licensed under the same terms as Go itself:
// https://code.google.com/p/go/source/browse/LICENSE
package http2
import (
"bytes"
"fmt"
"net/http"
"time"
"golang.org/x/net/http2/hpack"
)
// writeFramer is implemented by any type that is used to write frames.
type writeFramer interface {
writeFrame(writeContext) error
}
// writeContext is the interface needed by the various frame writer
// types below. All the writeFrame methods below are scheduled via the
// frame writing scheduler (see writeScheduler in writesched.go).
//
// This interface is implemented by *serverConn.
// TODO: use it from the client code too, once it exists.
type writeContext interface {
Framer() *Framer
Flush() error
CloseConn() error
// HeaderEncoder returns an HPACK encoder that writes to the
// returned buffer.
HeaderEncoder() (*hpack.Encoder, *bytes.Buffer)
}
// endsStream reports whether the given frame writer w will locally
// close the stream.
func endsStream(w writeFramer) bool {
switch v := w.(type) {
case *writeData:
return v.endStream
case *writeResHeaders:
return v.endStream
}
return false
}
type flushFrameWriter struct{}
func (flushFrameWriter) writeFrame(ctx writeContext) error {
return ctx.Flush()
}
type writeSettings []Setting
func (s writeSettings) writeFrame(ctx writeContext) error {
return ctx.Framer().WriteSettings([]Setting(s)...)
}
type writeGoAway struct {
maxStreamID uint32
code ErrCode
}
func (p *writeGoAway) writeFrame(ctx writeContext) error {
err := ctx.Framer().WriteGoAway(p.maxStreamID, p.code, nil)
if p.code != 0 {
ctx.Flush() // ignore error: we're hanging up on them anyway
time.Sleep(50 * time.Millisecond)
ctx.CloseConn()
}
return err
}
type writeData struct {
streamID uint32
p []byte
endStream bool
}
func (w *writeData) String() string {
return fmt.Sprintf("writeData(stream=%d, p=%d, endStream=%v)", w.streamID, len(w.p), w.endStream)
}
func (w *writeData) writeFrame(ctx writeContext) error {
return ctx.Framer().WriteData(w.streamID, w.endStream, w.p)
}
func (se StreamError) writeFrame(ctx writeContext) error {
return ctx.Framer().WriteRSTStream(se.StreamID, se.Code)
}
type writePingAck struct{ pf *PingFrame }
func (w writePingAck) writeFrame(ctx writeContext) error {
return ctx.Framer().WritePing(true, w.pf.Data)
}
type writeSettingsAck struct{}
func (writeSettingsAck) writeFrame(ctx writeContext) error {
return ctx.Framer().WriteSettingsAck()
}
// writeResHeaders is a request to write a HEADERS and 0+ CONTINUATION frames
// for HTTP response headers from a server handler.
type writeResHeaders struct {
streamID uint32
httpResCode int
h http.Header // may be nil
endStream bool
contentType string
contentLength string
}
func (w *writeResHeaders) writeFrame(ctx writeContext) error {
enc, buf := ctx.HeaderEncoder()
buf.Reset()
enc.WriteField(hpack.HeaderField{Name: ":status", Value: httpCodeString(w.httpResCode)})
for k, vv := range w.h {
k = lowerHeader(k)
for _, v := range vv {
// TODO: more of "8.1.2.2 Connection-Specific Header Fields"
if k == "transfer-encoding" && v != "trailers" {
continue
}
enc.WriteField(hpack.HeaderField{Name: k, Value: v})
}
}
if w.contentType != "" {
enc.WriteField(hpack.HeaderField{Name: "content-type", Value: w.contentType})
}
if w.contentLength != "" {
enc.WriteField(hpack.HeaderField{Name: "content-length", Value: w.contentLength})
}
headerBlock := buf.Bytes()
if len(headerBlock) == 0 {
panic("unexpected empty hpack")
}
// For now we're lazy and just pick the minimum MAX_FRAME_SIZE
// that all peers must support (16KB). Later we could care
// more and send larger frames if the peer advertised it, but
// there's little point. Most headers are small anyway (so we
// generally won't have CONTINUATION frames), and extra frames
// only waste 9 bytes anyway.
const maxFrameSize = 16384
first := true
for len(headerBlock) > 0 {
frag := headerBlock
if len(frag) > maxFrameSize {
frag = frag[:maxFrameSize]
}
headerBlock = headerBlock[len(frag):]
endHeaders := len(headerBlock) == 0
var err error
if first {
first = false
err = ctx.Framer().WriteHeaders(HeadersFrameParam{
StreamID: w.streamID,
BlockFragment: frag,
EndStream: w.endStream,
EndHeaders: endHeaders,
})
} else {
err = ctx.Framer().WriteContinuation(w.streamID, endHeaders, frag)
}
if err != nil {
return err
}
}
return nil
}
type write100ContinueHeadersFrame struct {
streamID uint32
}
func (w write100ContinueHeadersFrame) writeFrame(ctx writeContext) error {
enc, buf := ctx.HeaderEncoder()
buf.Reset()
enc.WriteField(hpack.HeaderField{Name: ":status", Value: "100"})
return ctx.Framer().WriteHeaders(HeadersFrameParam{
StreamID: w.streamID,
BlockFragment: buf.Bytes(),
EndStream: false,
EndHeaders: true,
})
}
type writeWindowUpdate struct {
streamID uint32 // or 0 for conn-level
n uint32
}
func (wu writeWindowUpdate) writeFrame(ctx writeContext) error {
return ctx.Framer().WriteWindowUpdate(wu.streamID, wu.n)
}