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/*
* Copyright (c) 2014 by Farsight Security, Inc.
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package framestream
import (
"bufio"
"encoding/binary"
"io"
"io/ioutil"
"time"
)
type ReaderOptions struct {
// The ContentTypes accepted by the Reader. May be left unset for no
// content negotiation. If the corresponding Writer offers a disjoint
// set of ContentTypes, NewReader() will return ErrContentTypeMismatch.
ContentTypes [][]byte
// If Bidirectional is true, the underlying io.Reader must be an
// io.ReadWriter, and the Reader will engage in a bidirectional
// handshake with its peer to establish content type and communicate
// shutdown.
Bidirectional bool
// Timeout gives the timeout for reading the initial handshake messages
// from the peer and writing response messages if Bidirectional. It is
// only effective for underlying Readers satisfying net.Conn.
Timeout time.Duration
}
// Reader reads data frames from an underlying io.Reader using the Frame
// Streams framing protocol.
type Reader struct {
contentType []byte
bidirectional bool
r *bufio.Reader
w *bufio.Writer
stopped bool
}
// NewReader creates a Frame Streams Reader reading from the given io.Reader
// with the given ReaderOptions.
func NewReader(r io.Reader, opt *ReaderOptions) (*Reader, error) {
if opt == nil {
opt = &ReaderOptions{}
}
tr := timeoutReader(r, opt)
reader := &Reader{
bidirectional: opt.Bidirectional,
r: bufio.NewReader(tr),
w: nil,
}
if len(opt.ContentTypes) > 0 {
reader.contentType = opt.ContentTypes[0]
}
var cf ControlFrame
if opt.Bidirectional {
w, ok := tr.(io.Writer)
if !ok {
return nil, ErrType
}
reader.w = bufio.NewWriter(w)
// Read the ready control frame.
err := cf.DecodeTypeEscape(reader.r, CONTROL_READY)
if err != nil {
return nil, err
}
// Check content type.
if t, ok := cf.ChooseContentType(opt.ContentTypes); ok {
reader.contentType = t
} else {
return nil, ErrContentTypeMismatch
}
// Send the accept control frame.
accept := ControlAccept
accept.SetContentType(reader.contentType)
err = accept.EncodeFlush(reader.w)
if err != nil {
return nil, err
}
}
// Read the start control frame.
err := cf.DecodeTypeEscape(reader.r, CONTROL_START)
if err != nil {
return nil, err
}
// Disable the read timeout to prevent killing idle connections.
disableReadTimeout(tr)
// Check content type.
if !cf.MatchContentType(reader.contentType) {
return nil, ErrContentTypeMismatch
}
return reader, nil
}
// ReadFrame reads a data frame into the supplied buffer, returning its length.
// If the frame is longer than the supplied buffer, Read returns
// ErrDataFrameTooLarge and discards the frame. Subsequent calls to Read()
// after this error may succeed.
func (r *Reader) ReadFrame(b []byte) (length int, err error) {
if r.stopped {
return 0, EOF
}
for length == 0 {
length, err = r.readFrame(b)
if err != nil {
return
}
}
return
}
// ContentType returns the content type negotiated with the Writer.
func (r *Reader) ContentType() []byte {
return r.contentType
}
func (r *Reader) readFrame(b []byte) (int, error) {
// Read the frame length.
var frameLen uint32
err := binary.Read(r.r, binary.BigEndian, &frameLen)
if err != nil {
return 0, err
}
if frameLen > uint32(len(b)) {
io.CopyN(ioutil.Discard, r.r, int64(frameLen))
return 0, ErrDataFrameTooLarge
}
if frameLen == 0 {
// This is a control frame.
var cf ControlFrame
err = cf.Decode(r.r)
if err != nil {
return 0, err
}
if cf.ControlType == CONTROL_STOP {
r.stopped = true
if r.bidirectional {
ff := &ControlFrame{ControlType: CONTROL_FINISH}
err = ff.EncodeFlush(r.w)
if err != nil {
return 0, err
}
}
return 0, EOF
}
return 0, err
}
return io.ReadFull(r.r, b[0:frameLen])
}
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