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/*
* Copyright (c) 2021 IBM Corp and others.
*
* All rights reserved. This program and the accompanying materials
* are made available under the terms of the Eclipse Public License v2.0
* and Eclipse Distribution License v1.0 which accompany this distribution.
*
* The Eclipse Public License is available at
* https://www.eclipse.org/legal/epl-2.0/
* and the Eclipse Distribution License is available at
* http://www.eclipse.org/org/documents/edl-v10.php.
*
* Contributors:
* Allan Stockdill-Mander
*/
package packets
import (
"bytes"
"fmt"
"io"
)
// PublishPacket is an internal representation of the fields of the
// Publish MQTT packet
type PublishPacket struct {
FixedHeader
TopicName string
MessageID uint16
Payload []byte
}
func (p *PublishPacket) String() string {
return fmt.Sprintf("%s topicName: %s MessageID: %d payload: %s", p.FixedHeader, p.TopicName, p.MessageID, string(p.Payload))
}
func (p *PublishPacket) Write(w io.Writer) error {
var body bytes.Buffer
var err error
body.Write(encodeString(p.TopicName))
if p.Qos > 0 {
body.Write(encodeUint16(p.MessageID))
}
p.FixedHeader.RemainingLength = body.Len() + len(p.Payload)
packet := p.FixedHeader.pack()
packet.Write(body.Bytes())
packet.Write(p.Payload)
_, err = w.Write(packet.Bytes())
return err
}
// Unpack decodes the details of a ControlPacket after the fixed
// header has been read
func (p *PublishPacket) Unpack(b io.Reader) error {
var payloadLength = p.FixedHeader.RemainingLength
var err error
p.TopicName, err = decodeString(b)
if err != nil {
return err
}
if p.Qos > 0 {
p.MessageID, err = decodeUint16(b)
if err != nil {
return err
}
payloadLength -= len(p.TopicName) + 4
} else {
payloadLength -= len(p.TopicName) + 2
}
if payloadLength < 0 {
return fmt.Errorf("error unpacking publish, payload length < 0")
}
p.Payload = make([]byte, payloadLength)
_, err = b.Read(p.Payload)
return err
}
// Copy creates a new PublishPacket with the same topic and payload
// but an empty fixed header, useful for when you want to deliver
// a message with different properties such as Qos but the same
// content
func (p *PublishPacket) Copy() *PublishPacket {
newP := NewControlPacket(Publish).(*PublishPacket)
newP.TopicName = p.TopicName
newP.Payload = p.Payload
return newP
}
// Details returns a Details struct containing the Qos and
// MessageID of this ControlPacket
func (p *PublishPacket) Details() Details {
return Details{Qos: p.Qos, MessageID: p.MessageID}
}
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