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decoder.go
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decoder.go
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package parser
import (
"bufio"
"bytes"
"encoding/json"
"io"
"io/ioutil"
"reflect"
"strings"
"github.com/googollee/go-socket.io/engineio/session"
"github.com/googollee/go-socket.io/logger"
)
const (
bufferTypeName = "Buffer"
)
type FrameReader interface {
NextReader() (session.FrameType, io.ReadCloser, error)
}
type byteReader interface {
io.Reader
ReadByte() (byte, error)
UnreadByte() error
}
type Decoder struct {
r FrameReader
lastFrame io.ReadCloser
packetReader byteReader
bufferCount uint64
isEvent bool
}
func NewDecoder(r FrameReader) *Decoder {
return &Decoder{
r: r,
}
}
func (d *Decoder) Close() error {
var err error
if d.lastFrame != nil {
err = d.lastFrame.Close()
d.lastFrame = nil
}
return err
}
func (d *Decoder) DiscardLast() (err error) {
if d.lastFrame != nil {
err = d.lastFrame.Close()
d.lastFrame = nil
}
return err
}
func (d *Decoder) DecodeHeader(header *Header, event *string) error {
ft, r, err := d.r.NextReader()
if err != nil {
return err
}
if ft != session.TEXT {
return errInvalidFirstPacketType
}
d.lastFrame = r
br, ok := r.(byteReader)
if !ok {
br = bufio.NewReader(r)
}
d.packetReader = br
bufferCount, err := d.readHeader(header)
if err != nil {
return err
}
d.bufferCount = bufferCount
if header.Type == binaryEvent || header.Type == binaryAck {
header.Type -= 3
}
d.isEvent = header.Type == Event
if d.isEvent {
if err := d.readEvent(event); err != nil {
return err
}
}
return nil
}
func (d *Decoder) DecodeArgs(types []reflect.Type) ([]reflect.Value, error) {
r := d.packetReader.(io.Reader)
if d.isEvent {
r = io.MultiReader(strings.NewReader("["), r)
}
ret := make([]reflect.Value, len(types))
values := make([]interface{}, len(types))
for i, typ := range types {
if typ.Kind() == reflect.Ptr {
typ = typ.Elem()
}
ret[i] = reflect.New(typ)
values[i] = ret[i].Interface()
}
if err := json.NewDecoder(r).Decode(&values); err != nil {
if err == io.EOF {
err = nil
}
_ = d.DiscardLast()
return nil, err
}
//we can't use defer or call DiscardLast before decoding, because
//there are buffered readers involved and if we invoke .Close() json will encounter unexpected EOF.
_ = d.DiscardLast()
for i, typ := range types {
if typ.Kind() != reflect.Ptr {
ret[i] = ret[i].Elem()
}
}
buffers := make([]Buffer, d.bufferCount)
for i := range buffers {
ft, r, err := d.r.NextReader()
if err != nil {
return nil, err
}
buffers[i].Data, err = d.readBuffer(ft, r)
if err != nil {
return nil, err
}
}
for i := range ret {
if err := d.detachBuffer(ret[i], buffers); err != nil {
return nil, err
}
}
return ret, nil
}
func (d *Decoder) readUint64FromText(r byteReader) (uint64, bool, error) {
var ret uint64
var hasRead bool
for {
b, err := r.ReadByte()
if err != nil {
if hasRead {
return ret, true, nil
}
return 0, false, err
}
if !('0' <= b && b <= '9') {
_ = r.UnreadByte()
return ret, hasRead, nil
}
hasRead = true
ret = ret*10 + uint64(b-'0')
}
}
func (d *Decoder) readString(r byteReader, until byte) (string, error) {
var ret bytes.Buffer
var hasRead bool
for {
b, err := r.ReadByte()
if err != nil {
if hasRead {
return ret.String(), nil
}
return "", err
}
if b == until {
return ret.String(), nil
}
if err := ret.WriteByte(b); err != nil {
return "", err
}
hasRead = true
}
}
func (d *Decoder) readHeader(header *Header) (uint64, error) {
typ, err := d.packetReader.ReadByte()
if err != nil {
return 0, err
}
header.Type = Type(typ - '0')
if header.Type > binaryAck {
return 0, ErrInvalidPacketType
}
num, hasNum, err := d.readUint64FromText(d.packetReader)
if err != nil {
if err == io.EOF {
err = nil
}
return 0, err
}
nextByte, err := d.packetReader.ReadByte()
if err != nil {
header.ID = num
header.NeedAck = hasNum
if err == io.EOF {
err = nil
}
return 0, err
}
// check if buffer count
var bufferCount uint64
if nextByte == '-' {
bufferCount = num
hasNum = false
num = 0
} else {
_ = d.packetReader.UnreadByte()
}
// check namespace
nextByte, err = d.packetReader.ReadByte()
if err != nil {
if err == io.EOF {
err = nil
}
return bufferCount, err
}
if nextByte == '/' {
_ = d.packetReader.UnreadByte()
header.Namespace, err = d.readString(d.packetReader, ',')
if err != nil {
if err == io.EOF {
err = nil
}
return bufferCount, err
}
queryPos := strings.IndexByte(header.Namespace, '?')
if queryPos > -1 {
header.Query = header.Namespace[queryPos+1:]
header.Namespace = header.Namespace[:queryPos]
}
} else {
_ = d.packetReader.UnreadByte()
}
// read id
header.ID, header.NeedAck, err = d.readUint64FromText(d.packetReader)
if err != nil {
if err == io.EOF {
err = nil
}
return bufferCount, err
}
if !header.NeedAck {
// 313["data"], id has been read at beginning, need add back.
header.ID = num
header.NeedAck = hasNum
}
return bufferCount, err
}
func (d *Decoder) readEvent(event *string) error {
b, err := d.packetReader.ReadByte()
if err != nil {
return err
}
if b != '[' {
_ = d.packetReader.UnreadByte()
return nil
}
var buf bytes.Buffer
for {
b, err := d.packetReader.ReadByte()
if err != nil {
return err
}
if b == ',' {
break
}
if b == ']' {
_ = d.packetReader.UnreadByte()
break
}
buf.WriteByte(b)
}
return json.Unmarshal(buf.Bytes(), event)
}
func (d *Decoder) readBuffer(ft session.FrameType, r io.ReadCloser) ([]byte, error) {
defer func() {
if err := r.Close(); err != nil {
logger.Error("close reader:", err)
}
}()
if ft != session.BINARY {
return nil, errInvalidBinaryBufferType
}
return ioutil.ReadAll(r)
}
func (d *Decoder) detachBuffer(v reflect.Value, buffers []Buffer) error {
for v.Kind() == reflect.Ptr || v.Kind() == reflect.Interface {
v = v.Elem()
}
switch v.Kind() {
case reflect.Struct:
if v.Type().Name() == bufferTypeName {
if !v.CanAddr() {
return errFailedBufferAddress
}
buffer := v.Addr().Interface().(*Buffer)
if buffer.isBinary {
*buffer = buffers[buffer.num]
}
return nil
}
for i := 0; i < v.NumField(); i++ {
if err := d.detachBuffer(v.Field(i), buffers); err != nil {
return err
}
}
case reflect.Map:
for _, key := range v.MapKeys() {
if err := d.detachBuffer(v.MapIndex(key), buffers); err != nil {
return err
}
}
case reflect.Array, reflect.Slice:
for i := 0; i < v.Len(); i++ {
if err := d.detachBuffer(v.Index(i), buffers); err != nil {
return err
}
}
}
return nil
}