翻出历史项目，先上传，未测试（MQTT3.1.1已经支持）

packet/packet.go

@@ -0,0 +1,102 @@
+package packet
+
+import (
+	"encoding/binary"
+	"fmt"
+)
+
+func LenLen(rl int) int {
+	if rl <= 127 { //0x7F
+		return 1
+	} else if rl <= 16383 { //0x7F 7F
+		return 2
+	} else if rl <= 2097151 { //0x7F 7F 7F
+		return 3
+	} else {
+		return 4
+	}
+}
+
+func ReadRemainLength(b []byte) (int, int, error) {
+	length := len(b)
+	size := 1
+	for {
+		if length < size {
+			return 0, size, fmt.Errorf("[ReadRemainLength] Expect at leat %d bytes", 1)
+		}
+
+		if b[size-1] > 0x80 {
+			size += 1
+		} else {
+			break
+		}
+
+		if size > 4 {
+			return 0, size, fmt.Errorf("[ReadRemainLength] Expect at most 4 bytes, got %d", size)
+		}
+	}
+	rl, size := binary.Uvarint(b)
+	return int(rl), size, nil
+}
+
+func WriteRemainLength(b []byte, rl int) (int, error) {
+	length := len(b)
+	ll := LenLen(rl)
+	if ll > length {
+		return 0, fmt.Errorf("[ReadRemainLength] Expect at most %d bytes for remain length", ll)
+	}
+	return binary.PutUvarint(b, uint64(rl)), nil
+}
+
+func ReadBytes(buf []byte) ([]byte, int, error) {
+	if len(buf) < 2 {
+		return nil, 0, fmt.Errorf("[readLPBytes] Expect at least %d bytes for prefix", 2)
+	}
+	length := int(binary.BigEndian.Uint16(buf))
+	total := length + 2
+	if len(buf) < total {
+		return nil, 0, fmt.Errorf("[readLPBytes] Expect at least %d bytes", length+2)
+	}
+	b := buf[2 : total]
+	return b, total, nil
+}
+
+func WriteBytes(buf []byte, b []byte) (int, error) {
+	length, size := len(b), len(buf)
+
+	if length > 65535 {
+		return 0, fmt.Errorf("[writeLPBytes] Too much bytes(%d) to write", length)
+	}
+
+	total := length + 2
+	if size < total {
+		return 0, fmt.Errorf("[writeLPBytes] Expect at least %d bytes", total)
+	}
+
+	binary.BigEndian.PutUint16(buf, uint16(length))
+
+	copy(buf[2:], b)
+
+	return total, nil
+}
+
+func BytesDup(buf []byte) []byte {
+	b := make([]byte, len(buf))
+	copy(b, buf)
+	return b
+}
+
+func Decode(buf []byte) (Message, int, error) {
+	mt := MsgType(buf[0] >> 4)
+	msg := mt.NewMessage()
+	if msg != nil {
+		l, err := msg.Decode(buf)
+		return msg, l, err
+	} else {
+		return nil, 0, fmt.Errorf("Unknown messege type")
+	}
+}
+
+func Encode(msg Message) ([]byte, []byte, error) {
+	return msg.Encode()
+}