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package packets
import (
"bytes"
"encoding/binary"
"fmt"
"io"
)
const magicBytes = "EKO"
const (
FlagHandshake byte = 0b1000_0000
FlagV1 byte = 0b0000_0000
)
type Packet struct {
flag byte
data []byte
}
func NewPacket(flag byte, data []byte) Packet {
return Packet{flag, data}
}
func (p Packet) Write(w io.Writer) error {
if err := binary.Write(w, binary.LittleEndian, magicBytes); err != nil {
return err
}
if err := binary.Write(w, binary.LittleEndian, p.flag); err != nil {
return err
}
if err := binary.Write(w, binary.LittleEndian, uint32(len(p.data))); err != nil {
return err
}
if err := binary.Write(w, binary.LittleEndian, p.data); err != nil {
return err
}
return nil
}
func ReadPacket(r io.Reader) (Packet, error) {
buffer := [len(magicBytes) + 1 + 4]byte{}
bytesRead, err := r.Read(buffer[:])
if bytesRead != len(buffer) {
if err != nil && err != io.EOF {
return Packet{}, err
}
return Packet{}, fmt.Errorf("invalid packet size: got %v, want %v", bytesRead, len(buffer))
}
magic := buffer[:len(magicBytes)]
if !bytes.Equal(magic, []byte(magicBytes)) {
return Packet{}, fmt.Errorf("invalid magic number: got %v, want %v", magic, magicBytes)
}
flag := buffer[len(magicBytes)]
// TODO: Consider adding some data limit (maybe 65k?)
var length uint32
err = binary.Read(
bytes.NewReader(buffer[len(magicBytes):len(magicBytes)+4]),
binary.LittleEndian,
&length,
)
if err != nil {
panic(fmt.Errorf("Assertion Failed in packet.ReadPacket(io.Reader): %v", err))
}
data := make([]byte, length)
bytesRead, err = r.Read(data)
if uint32(bytesRead) != length {
if err != nil {
return Packet{}, err
}
return Packet{}, fmt.Errorf("invalid data size: got %v, want %v", bytesRead, length)
}
return Packet{flag, data}, nil
}
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