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80 lines
1.9 KiB
80 lines
1.9 KiB
package packets
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import (
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"bytes"
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"fmt"
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"io"
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)
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//PublishPacket is an internal representation of the fields of the
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//Publish MQTT packet
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type PublishPacket struct {
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FixedHeader
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TopicName string
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MessageID uint16
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Payload []byte
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}
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func (p *PublishPacket) String() string {
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str := fmt.Sprintf("%s", p.FixedHeader)
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str += " "
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str += fmt.Sprintf("topicName: %s MessageID: %d", p.TopicName, p.MessageID)
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str += " "
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str += fmt.Sprintf("payload: %s", string(p.Payload))
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return str
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}
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func (p *PublishPacket) Write(w io.Writer) error {
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var body bytes.Buffer
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var err error
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body.Write(encodeString(p.TopicName))
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if p.Qos > 0 {
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body.Write(encodeUint16(p.MessageID))
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}
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p.FixedHeader.RemainingLength = body.Len() + len(p.Payload)
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packet := p.FixedHeader.pack()
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packet.Write(body.Bytes())
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packet.Write(p.Payload)
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_, err = w.Write(packet.Bytes())
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return err
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}
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//Unpack decodes the details of a ControlPacket after the fixed
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//header has been read
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func (p *PublishPacket) Unpack(b io.Reader) error {
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var payloadLength = p.FixedHeader.RemainingLength
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p.TopicName = decodeString(b)
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if p.Qos > 0 {
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p.MessageID = decodeUint16(b)
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payloadLength -= len(p.TopicName) + 4
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} else {
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payloadLength -= len(p.TopicName) + 2
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}
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if payloadLength < 0 {
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return fmt.Errorf("Error upacking publish, payload length < 0")
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}
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p.Payload = make([]byte, payloadLength)
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_, err := b.Read(p.Payload)
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return err
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}
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//Copy creates a new PublishPacket with the same topic and payload
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//but an empty fixed header, useful for when you want to deliver
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//a message with different properties such as Qos but the same
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//content
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func (p *PublishPacket) Copy() *PublishPacket {
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newP := NewControlPacket(Publish).(*PublishPacket)
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newP.TopicName = p.TopicName
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newP.Payload = p.Payload
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return newP
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}
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//Details returns a Details struct containing the Qos and
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//MessageID of this ControlPacket
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func (p *PublishPacket) Details() Details {
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return Details{Qos: p.Qos, MessageID: p.MessageID}
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}
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