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reader.go
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reader.go
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package mqtt
import (
"bufio"
"encoding/binary"
"io"
"sync"
"unicode/utf8"
)
// ReaderOption is an option for the PacketReader.
type ReaderOption interface {
apply(*PacketReader)
}
type readerOptionFunc func(*PacketReader)
func (f readerOptionFunc) apply(r *PacketReader) {
f(r)
}
// WithMaxPacketLength returns a ReaderOption that configures a maximum packet
// length on the Reader.
func WithMaxPacketLength(bytes uint32) ReaderOption {
return readerOptionFunc(func(r *PacketReader) {
r.maxPacketLength = bytes
})
}
type reader interface {
io.Reader
io.ByteReader
}
// PacketReader reads MQTT packets.
type PacketReader struct {
maxPacketLength uint32
r reader
protocol byte
mu sync.Mutex
nRead uint32
header FixedHeader
packet Packet
err error
}
// SetProtocol sets the MQTT protocol version.
func (r *PacketReader) SetProtocol(protocol byte) {
r.mu.Lock()
r.protocol = protocol
r.mu.Unlock()
}
// NewReader returns a new Reader on top of the given io.Reader.
func NewReader(rd io.Reader, opts ...ReaderOption) *PacketReader {
pr := &PacketReader{
protocol: DefaultProtocolVersion,
}
if r, ok := rd.(reader); ok {
pr.r = r
} else {
pr.r = bufio.NewReader(rd)
}
for _, opt := range opts {
opt.apply(pr)
}
return pr
}
var errUnknownPacket = NewReasonCodeError(ProtocolError, "mqtt: unknown packet")
func (r *PacketReader) readVariableHeader() {
switch r.packet.PacketType() {
case CONNECT:
r.readConnectHeader()
r.protocol = r.packet.(*ConnectPacket).ConnectHeader.ProtocolVersion
case CONNACK:
r.readConnackHeader()
case PUBLISH:
r.readPublishHeader()
case PUBACK:
r.readPubackHeader()
case PUBREC:
r.readPubrecHeader()
case PUBREL:
r.readPubrelHeader()
case PUBCOMP:
r.readPubcompHeader()
case SUBSCRIBE:
r.readSubscribeHeader()
case SUBACK:
r.readSubackHeader()
case UNSUBSCRIBE:
r.readUnsubscribeHeader()
case UNSUBACK:
r.readUnsubackHeader()
case DISCONNECT:
r.readDisconnectHeader()
case AUTH:
if r.protocol < 5 {
r.err = errUnknownPacket
return
}
r.readAuthHeader()
}
}
var errRemainingData = NewReasonCodeError(ProtocolError, "mqtt: unexpected remaining data after reading packet")
func (r *PacketReader) readPayload() {
switch r.packet.PacketType() {
case CONNECT:
r.readConnectPayload()
case PUBLISH:
r.readPublishPayload()
case SUBSCRIBE:
r.readSubscribePayload()
case SUBACK:
r.readSubackPayload()
case UNSUBSCRIBE:
r.readUnsubscribePayload()
case UNSUBACK:
r.readUnsubackPayload()
default:
if r.remaining() > 0 {
r.err = errRemainingData
}
}
}
// ReadPacket reads the next packet.
func (r *PacketReader) ReadPacket() (Packet, error) {
r.mu.Lock()
defer r.mu.Unlock()
r.nRead = 0
r.readFixedHeader()
if r.err != nil {
return nil, r.err
}
switch r.header.PacketType() {
case CONNECT:
r.packet = new(ConnectPacket)
case CONNACK:
r.packet = new(ConnackPacket)
case PUBLISH:
packet := new(PublishPacket)
packet.PublishFlags = PublishFlags(r.header.typeAndFlags) & 0xf
r.packet = packet
case PUBACK:
r.packet = new(PubackPacket)
case PUBREC:
r.packet = new(PubrecPacket)
case PUBREL:
r.packet = new(PubrelPacket)
case PUBCOMP:
r.packet = new(PubcompPacket)
case SUBSCRIBE:
r.packet = new(SubscribePacket)
case SUBACK:
r.packet = new(SubackPacket)
case UNSUBSCRIBE:
r.packet = new(UnsubscribePacket)
case UNSUBACK:
r.packet = new(UnsubackPacket)
case PINGREQ:
r.packet = new(PingreqPacket)
case PINGRESP:
r.packet = new(PingrespPacket)
case DISCONNECT:
r.packet = new(DisconnectPacket)
case AUTH:
r.packet = new(AuthPacket)
}
r.nRead = 0
r.readVariableHeader()
if r.err != nil {
return nil, r.err
}
r.readPacketProperties()
if r.err != nil {
return nil, r.err
}
r.readPayload()
if r.err != nil {
return nil, r.err
}
return r.packet, nil
}
var errInsufficientRemainingBytes = NewReasonCodeError(MalformedPacket, "insufficient remaining bytes")
func (r *PacketReader) read(b []byte) error {
if r.remaining() < uint32(len(b)) {
return errInsufficientRemainingBytes
}
n, err := io.ReadFull(r.r, b)
if err != nil {
return err
}
r.nRead += uint32(n)
return nil
}
func (r *PacketReader) readByte() (b byte, err error) {
if r.remaining() < 1 {
return 0, errInsufficientRemainingBytes
}
b, err = r.r.ReadByte()
if err != nil {
return 0, err
}
r.nRead++
return
}
func (r *PacketReader) readUint16() (uint16, error) {
var b [2]byte
err := r.read(b[:])
if err != nil {
return 0, err
}
return binary.BigEndian.Uint16(b[:]), nil
}
func (r *PacketReader) readUint32() (uint32, error) {
var b [4]byte
err := r.read(b[:])
if err != nil {
return 0, err
}
return binary.BigEndian.Uint32(b[:]), nil
}
type countingByteReader struct {
*PacketReader
}
func (r *PacketReader) readUvarint() (i uint64, err error) {
return binary.ReadUvarint(countingByteReader{r})
}
func (r countingByteReader) ReadByte() (byte, error) {
return r.PacketReader.readByte()
}
func (r *PacketReader) readBytes() ([]byte, error) {
var length uint16
length, err := r.readUint16()
if err != nil {
return nil, err
}
if length == 0 {
return nil, nil
}
b := make([]byte, length)
err = r.read(b)
if err != nil {
return nil, err
}
return b, nil
}
var errInvalidUTF8 = NewReasonCodeError(MalformedPacket, "mqtt: invalid utf-8 string")
func (r *PacketReader) readString() ([]byte, error) {
b, err := r.readBytes()
if err != nil {
return nil, err
}
if r.protocol >= 4 && !utf8.Valid(b) {
return nil, errInvalidUTF8
}
return b, nil
}
func (r *PacketReader) readStringPair() (k, v []byte, err error) {
k, err = r.readString()
if err != nil {
return nil, nil, err
}
v, err = r.readString()
if err != nil {
return nil, nil, err
}
return k, v, nil
}
func (r *PacketReader) remaining() uint32 {
return r.header.remainingLength - r.nRead
}
func (r *PacketReader) readRemaining() ([]byte, error) {
b := make([]byte, int(r.remaining()))
err := r.read(b)
if err != nil {
return nil, err
}
return b, nil
}