maeqtt/mqtt/types/Encoding.go

package types

import (
	"encoding/binary"
	"errors"
	"io"
)

func WriteBits(w io.Writer, data [8]bool) error {
	encoded := byte(0)
	for i, v := range data {
		encoded = encoded | byte(BoolToUint(v)<<i)
	}
	_, err := w.Write([]byte{encoded})
	return err
}

func WriteUint16(w io.Writer, v uint16) error {
	buf := make([]byte, 2)
	binary.BigEndian.PutUint16(buf, v)
	_, err := w.Write(buf)
	return err
}

func WriteUint32(w io.Writer, v uint32) error {
	buf := make([]byte, 4)
	binary.BigEndian.PutUint32(buf, v)
	_, err := w.Write(buf)
	return err
}

const uint32Max uint32 = ^uint32(0)

func WriteDataWithVarIntLen(w io.Writer, data []byte) error {
	if len(data) > int(uint32Max) {
		return errors.New("Tried to write more data than max varint size")
	}

	err := WriteVariableByteInt(w, uint32(len(data)))
	if err != nil {
		return err
	}

	_, err = w.Write(data)
	return err
}

const uint16Max uint16 = ^uint16(0)

func WriteBinaryData(w io.Writer, data []byte) error {
	if len(data) > int(uint16Max) {
		return errors.New("Tried to write more data than max uint16 size")
	}

	err := WriteUint16(w, uint16(len(data)))
	if err != nil {
		return err
	}

	_, err = w.Write(data)
	return err
}

func WriteUTF8String(w io.Writer, str string) error {
	return WriteBinaryData(w, []byte(str))
}

func WriteVariableByteInt(w io.Writer, v uint32) error {
	for {
		encodedByte := byte(v % 128)
		v = v / 128

		if v > 0 {
			encodedByte = encodedByte | 128
		}

		_,err := w.Write([]byte{encodedByte})
		if err != nil {
			return err
		}

		if v == 0 {
			return nil
		}
	}
}