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publish.go
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publish.go
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// Copyright (c) 2016 The MQPP Authors. All rights reserved.
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
// http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.
package mqpp
// Publish mqtt publish message, structure:
// fixed header
// variable header: Topic Name, Packet Identifier
// payload: content
type Publish struct {
endecBytes
topicNamePos int
packetIDPos int
payloadPos int
}
func newPublish(data []byte) (*Publish, error) {
if len(data) < 1 || data[0]>>4 != TPUBLISH {
return nil, ErrProtocolViolation
}
p := &Publish{endecBytes: data}
fixedHeader, offset := p.byte(0)
qos := fixedHeader << 5 >> 6
remlen, offset := p.remlen(offset)
if offset <= 1 {
return nil, ErrMalformedRemLen
}
pktLen := offset + int(remlen)
if len(data) < pktLen {
return nil, ErrProtocolViolation
}
p.topicNamePos = offset
_, offset = p.string(p.topicNamePos)
if qos > QosAtMostOnce {
p.packetIDPos = offset
_, offset = p.uint16(offset)
}
p.payloadPos = offset
return p, nil
}
// MakePublish create a mqtt publish packet
func MakePublish(dup bool, qos byte, retain bool, topicName string, packetIdentifier uint16, payload []byte) Publish {
p := Publish{}
remlen := p.calc(topicName, payload)
if qos > QosAtMostOnce {
remlen += p.calc(packetIdentifier)
}
pktLen := 1 + p.calc(uint32(remlen)) + remlen
p.endecBytes = make([]byte, pktLen)
offset := p.fill(0, (TPUBLISH<<4)|(qos<<1))
p.set(0, 3, dup).set(0, 0, retain)
p.topicNamePos = p.fill(offset, uint32(remlen))
offset = p.fill(p.topicNamePos, topicName)
if qos > QosAtMostOnce {
p.packetIDPos = offset
offset = p.fill(p.packetIDPos, packetIdentifier)
}
p.payloadPos = offset
p.fill(p.payloadPos, payload)
return p
}
// Dup return is dup
func (p *Publish) Dup() bool {
return p.bit(0, 3)
}
// QoS return qos
func (p *Publish) QoS() byte {
qos, _ := p.byte(0)
return qos << 5 >> 6
}
// Retain return is retain set
func (p *Publish) Retain() bool {
return p.bit(0, 0)
}
// TopicName return topic name
func (p *Publish) TopicName() string {
topic, _ := p.string(p.topicNamePos)
return topic
}
// PacketIdentifier return packet id if qos > 0, or zero when qos = 0
func (p *Publish) PacketIdentifier() uint16 {
if p.QoS() > QosAtMostOnce {
pid, _ := p.uint16(p.packetIDPos)
return pid
}
return 0
}
// Payload return publish content
func (p *Publish) Payload() []byte {
return p.bytes(p.payloadPos)
}