frame.go

/*
 * Copyright (c) 2021. Lorem ipsum dolor sit amet, consectetur adipiscing elit.
 * Morbi non lorem porttitor neque feugiat blandit. Ut vitae ipsum eget quam lacinia accumsan.
 * Etiam sed turpis ac ipsum condimentum fringilla. Maecenas magna.
 * Proin dapibus sapien vel ante. Aliquam erat volutpat. Pellentesque sagittis ligula eget metus.
 * Vestibulum commodo. Ut rhoncus gravida arcu.
 */

package utils

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

const frameCode uint32 = 0x656f7363 // frameCode = "eosc"
var (
	ErrorInvalidFrame = errors.New("invalid frame")
)

func ReadFrame(r io.Reader) ([]byte, error) {

	heater := make([]byte, 4)
	_, err := io.ReadFull(r, heater)
	if err != nil {
		return nil, err
	}

	code := binary.BigEndian.Uint32(heater)
	if code != frameCode {
		return nil, ErrorInvalidFrame
	}

	_, err = io.ReadFull(r, heater)
	if err != nil {
		return nil, err
	}
	size := binary.BigEndian.Uint32(heater)

	buf := make([]byte, size)
	_, err = io.ReadFull(r, buf)
	if err != nil {
		return nil, err
	}
	return buf, nil
}

func WriteFrame(w io.Writer, data []byte) error {
	size := len(data)

	err := binary.Write(w, binary.BigEndian, frameCode)
	if err != nil {
		return err
	}
	err = binary.Write(w, binary.BigEndian, uint32(size))
	if err != nil {
		return err
	}
	_, err = w.Write(data)
	return err
}

func DecodeFrame(data []byte) ([]byte, error) {
	return ReadFrame(bytes.NewBuffer(data))
}
func EncodeFrame(data []byte) []byte {
	size := len(data)
	buf := make([]byte, size+8)
	binary.BigEndian.PutUint32(buf[0:4], frameCode)
	binary.BigEndian.PutUint32(buf[4:8], uint32(size))
	copy(buf[8:], data)
	return buf
}