daemon-socket-go-example/frameconn.go

package main

import (
	"encoding/binary"
	"io"
)

type Typed interface {
	Type() uint32
}

type Framed interface {
	Value() []byte
}

type Frame interface {
	Typed
	Framed
}

type frame struct {
	typeID     uint32
	valueBytes []byte
}

func (f frame) Type() uint32 {
	return f.typeID
}

func (f frame) Value() []byte {
	return f.valueBytes
}

// FrameReadWriter is a struct encapsulating io.ReadWriter, which provides additional methods for reading and
// writing frames -- messages which have their own type and value byte buffer.
// Data sent or received using this socket is expected to be encoded in LTV format, which means:
// L - 4 bytes of frame length, big endian encoded
// T - 4 bytes of frame type, big endian encoded
// V - L bytes of frame data bytes
type FrameReadWriter struct {
	io.ReadWriter
}

func (frw FrameReadWriter) ReadFrame() (Frame, error) {
	lengthBytes := make([]byte, 4)
	_, err := io.ReadFull(frw, lengthBytes)
	if err != nil {
		return nil, err
	}

	frameLength := binary.BigEndian.Uint32(lengthBytes)

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

	frameType := binary.LittleEndian.Uint32(typeBytes)
	frameBytes := make([]byte, frameLength)
	_, err = io.ReadFull(frw, frameBytes)
	if err != nil {
		return nil, err
	}

	result := frame{typeID: frameType, valueBytes: frameBytes}

	return result, nil
}

func (frw FrameReadWriter) WriteFrame(f Frame) error {
	frameLength := len(f.Value())
	lengthBytes := make([]byte, 4)
	binary.BigEndian.PutUint32(lengthBytes, uint32(frameLength))

	typeBytes := make([]byte, 4)
	binary.BigEndian.PutUint32(typeBytes, f.Type())

	result := make([]byte, 0)
	result = append(result, lengthBytes...)
	result = append(result, typeBytes...)
	result = append(result, f.Value()...)

	_, err := frw.Write(result)
	if err != nil {
		return err
	}

	return nil
}