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subscribe.go
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subscribe.go
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package mqtt
import (
"bytes"
"errors"
"fmt"
"io"
"strings"
"github.com/srishina/mqtt.go/internal/mqttutil"
"github.com/srishina/mqtt.go/internal/properties"
)
var (
ErrNoTopicsPresent = errors.New("Subscription payload MUST contain atleast a topic - protocol error")
)
// SubscribeProperties MQTT SUBSCRIBE properties
type SubscribeProperties struct {
SubscriptionIdentifier *uint32
UserProperty map[string]string
}
func (sp *SubscribeProperties) String() string {
var fields []string
if sp.SubscriptionIdentifier != nil {
fields = append(fields, fmt.Sprintf("Subscription identifier: %d", *sp.SubscriptionIdentifier))
}
return fmt.Sprintf("{%s}", strings.Join(fields, ","))
}
func (sp *SubscribeProperties) length() uint32 {
propertyLen := uint32(0)
propertyLen += properties.EncodedSize.FromVarUin32((sp.SubscriptionIdentifier))
propertyLen += properties.EncodedSize.FromUTF8StringPair(sp.UserProperty)
return propertyLen
}
func (sp *SubscribeProperties) encode(buf *bytes.Buffer, propertyLen uint32) error {
if err := properties.Encoder.FromVarUint32(
buf, properties.SubscriptionIdentifierID, sp.SubscriptionIdentifier); err != nil {
return err
}
if err := properties.Encoder.FromUTF8StringPair(
buf, properties.UserPropertyID, sp.UserProperty); err != nil {
return err
}
return nil
}
func (sp *SubscribeProperties) decode(r io.Reader, propertyLen uint32) error {
var id uint32
var err error
for err == nil && propertyLen > 0 {
id, _, err = mqttutil.DecodeVarUint32(r)
if err != nil {
return err
}
propertyLen -= mqttutil.EncodedVarUint32Size(id)
propID := properties.PropertyID(id)
switch properties.PropertyID(id) {
case properties.SubscriptionIdentifierID:
sp.SubscriptionIdentifier, err = properties.DecoderOnlyOnce.ToVarUint32(r, propID, sp.SubscriptionIdentifier)
if err == nil && *sp.SubscriptionIdentifier == 0 {
err = fmt.Errorf("%s must not be 0", propID.Text())
}
propertyLen -= mqttutil.EncodedVarUint32Size(*sp.SubscriptionIdentifier)
case properties.UserPropertyID:
if sp.UserProperty == nil {
sp.UserProperty = make(map[string]string)
}
key, value, err2 := properties.Decoder.ToUTF8StringPair(r)
if err2 != nil {
return err2
}
sp.UserProperty[key] = value
propertyLen -= uint32(len(key) + len(value) + 4)
default:
return fmt.Errorf("SUBSCRIBE: wrong property with identifier %d", id)
}
}
return err
}
// Subscription contains topic filter and subscription options for the MQTT subscribe
type Subscription struct {
TopicFilter string
QoSLevel byte
NoLocal bool
RetainAsPublished bool
RetainHandling byte
}
func (s *Subscription) String() string {
return fmt.Sprintf(`Topic filter: %s QoS level: %d No Local? %t
Retain as published? %t Retain handling: %d`, s.TopicFilter, s.QoSLevel, s.NoLocal, s.RetainAsPublished, s.RetainHandling)
}
// Subscribe MQTT SUBSCRIBE packet
type Subscribe struct {
packetID uint16
Subscriptions []*Subscription
Properties *SubscribeProperties
}
func (s *Subscribe) String() string {
return fmt.Sprintf(`Subscriptions: [% v] Properties: %s`, s.Subscriptions, s.Properties)
}
func (s *Subscribe) propertyLength() uint32 {
if s.Properties != nil {
return s.Properties.length()
}
return 0
}
func (s *Subscribe) encodeProperties(buf *bytes.Buffer, propertyLen uint32) error {
if err := mqttutil.EncodeVarUint32(buf, propertyLen); err != nil {
return err
}
if s.Properties != nil {
return s.Properties.encode(buf, propertyLen)
}
return nil
}
func (s *Subscribe) decodeProperties(r io.Reader) error {
propertyLen, _, err := mqttutil.DecodeVarUint32(r)
if err != nil {
return err
}
if propertyLen > 0 {
s.Properties = &SubscribeProperties{}
return s.Properties.decode(r, propertyLen)
}
return nil
}
// encode encode the SUBSCRIBE packet
func (s *Subscribe) encode(w io.Writer) error {
const fixedHeader = byte(0x82) // 10000010
if len(s.Subscriptions) == 0 {
return ErrNoTopicsPresent
}
propertyLen := s.propertyLength()
// calculate the remaining length
// 2 = packet ID
remainingLength := 2 + propertyLen + mqttutil.EncodedVarUint32Size(propertyLen)
// add subscriptions length
for _, subscription := range s.Subscriptions {
// subscibe topic filter length, topic filter and it's optionss
remainingLength += uint32(len(subscription.TopicFilter) + 2 + 1)
}
var packet bytes.Buffer
packet.Grow(int(1 + remainingLength + mqttutil.EncodedVarUint32Size(remainingLength)))
if err := mqttutil.EncodeByte(&packet, fixedHeader); err != nil {
return err
}
if err := mqttutil.EncodeVarUint32(&packet, remainingLength); err != nil {
return err
}
if err := mqttutil.EncodeBigEndianUint16(&packet, s.packetID); err != nil {
return err
}
if err := s.encodeProperties(&packet, propertyLen); err != nil {
return err
}
for _, subscription := range s.Subscriptions {
if err := mqttutil.EncodeUTF8String(&packet, subscription.TopicFilter); err != nil {
return err
}
var b byte
// write subscribe options
b |= subscription.QoSLevel & 0x03
if subscription.NoLocal {
b |= 0x04
}
if subscription.RetainAsPublished {
b |= 0x08
}
b |= (subscription.RetainHandling & 0x30)
if err := mqttutil.EncodeByte(&packet, b); err != nil {
return err
}
}
_, err := packet.WriteTo(w)
return err
}
// decode decode the SUBSCRIBE packet
func (s *Subscribe) decode(r io.Reader, remainingLen uint32) error {
var err error
s.packetID, err = mqttutil.DecodeBigEndianUint16(r)
if err != nil {
return err
}
err = s.decodeProperties(r)
if err != nil {
return err
}
propertyLen := s.propertyLength()
remainingLen -= (uint32(2) + propertyLen + mqttutil.EncodedVarUint32Size(propertyLen))
for remainingLen > 0 {
topicFilter, _, err := mqttutil.DecodeUTF8String(r)
if err != nil {
return err
}
b, err := mqttutil.DecodeByte(r)
if err != nil {
return err
}
qosLevel := (b & 0x03)
nl := (b & 0x04) == 1
rap := (b & 0x08) == 1
rh := b & 0x30
s.Subscriptions = append(s.Subscriptions,
&Subscription{TopicFilter: topicFilter, QoSLevel: qosLevel, NoLocal: nl, RetainAsPublished: rap, RetainHandling: rh})
remainingLen -= uint32(len(topicFilter) + 2 + 1)
}
if len(s.Subscriptions) == 0 {
return ErrNoTopicsPresent
}
return nil
}