154 lines
3.1 KiB
Go
154 lines
3.1 KiB
Go
/*
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* Copyright (c) 2014 by Farsight Security, Inc.
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*
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* Licensed under the Apache License, Version 2.0 (the "License");
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* you may not use this file except in compliance with the License.
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* You may obtain a copy of the License at
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*
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* http://www.apache.org/licenses/LICENSE-2.0
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*
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* Unless required by applicable law or agreed to in writing, software
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* distributed under the License is distributed on an "AS IS" BASIS,
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* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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* See the License for the specific language governing permissions and
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* limitations under the License.
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*/
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package framestream
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import (
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"bufio"
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"encoding/binary"
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"io"
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)
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type DecoderOptions struct {
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MaxPayloadSize uint32
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ContentType []byte
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Bidirectional bool
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}
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type Decoder struct {
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buf []byte
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opt DecoderOptions
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reader *bufio.Reader
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writer *bufio.Writer
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stopped bool
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}
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func NewDecoder(r io.Reader, opt *DecoderOptions) (dec *Decoder, err error) {
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if opt == nil {
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opt = &DecoderOptions{}
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}
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if opt.MaxPayloadSize == 0 {
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opt.MaxPayloadSize = DEFAULT_MAX_PAYLOAD_SIZE
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}
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dec = &Decoder{
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buf: make([]byte, opt.MaxPayloadSize),
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opt: *opt,
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reader: bufio.NewReader(r),
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writer: nil,
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}
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var cf ControlFrame
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if opt.Bidirectional {
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w, ok := r.(io.Writer)
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if !ok {
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return dec, ErrType
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}
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dec.writer = bufio.NewWriter(w)
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// Read the ready control frame.
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err = cf.DecodeTypeEscape(dec.reader, CONTROL_READY)
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if err != nil {
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return
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}
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// Check content type.
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if !cf.MatchContentType(dec.opt.ContentType) {
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return dec, ErrContentTypeMismatch
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}
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// Send the accept control frame.
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accept := ControlAccept
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accept.SetContentType(dec.opt.ContentType)
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err = accept.EncodeFlush(dec.writer)
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if err != nil {
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return
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}
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}
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// Read the start control frame.
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err = cf.DecodeTypeEscape(dec.reader, CONTROL_START)
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if err != nil {
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return
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}
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// Check content type.
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if !cf.MatchContentType(dec.opt.ContentType) {
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return dec, ErrContentTypeMismatch
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}
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return
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}
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func (dec *Decoder) readFrame(frameLen uint32) (err error) {
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// Enforce limits on frame size.
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if frameLen > dec.opt.MaxPayloadSize {
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err = ErrDataFrameTooLarge
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return
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}
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// Read the frame.
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n, err := io.ReadFull(dec.reader, dec.buf[0:frameLen])
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if err != nil || uint32(n) != frameLen {
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return
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}
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return
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}
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func (dec *Decoder) Decode() (frameData []byte, err error) {
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if dec.stopped {
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err = EOF
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return
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}
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// Read the frame length.
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var frameLen uint32
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err = binary.Read(dec.reader, binary.BigEndian, &frameLen)
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if err != nil {
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return
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}
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if frameLen == 0 {
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// This is a control frame.
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var cf ControlFrame
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err = cf.Decode(dec.reader)
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if err != nil {
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return
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}
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if cf.ControlType == CONTROL_STOP {
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dec.stopped = true
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if dec.opt.Bidirectional {
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ff := &ControlFrame{ControlType: CONTROL_FINISH}
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err = ff.EncodeFlush(dec.writer)
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if err != nil {
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return
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}
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}
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return nil, EOF
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}
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if err != nil {
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return nil, err
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}
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} else {
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// This is a data frame.
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err = dec.readFrame(frameLen)
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if err != nil {
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return
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}
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frameData = dec.buf[0:frameLen]
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}
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return
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}
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