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package core
import (
"bytes"
"encoding/binary"
"fmt"
"io"
"time"
)
type Wrapper interface {
Wrap() (PayloadType, []any)
}
type PayloadType uint8
const (
PayloadUnknown PayloadType = 0x00
PayloadHandshake = 0x01
PayloadPing = 0x02
PayloadPong = 0x03
PayloadMessage = 0x04
PayloadTest = 0xFF
)
type Frame struct {
Length uint16
Type PayloadType
Payload []any
}
type Binary struct {
Length uint16
Payload []byte
}
func Encode(w Wrapper) ([]byte, error) {
payloadType, payload := w.Wrap()
buf := bytes.NewBuffer(make([]byte, 3))
for _, p := range payload {
switch v := p.(type) {
case string:
err := binary.Write(buf, binary.BigEndian, uint16(len(v)))
if err != nil {
return []byte{}, fmt.Errorf("cannot encode string length: %v", err)
}
_, err = buf.WriteString(v)
if err != nil {
return []byte{}, fmt.Errorf("cannot encode string: %v", err)
}
case []byte:
err := binary.Write(buf, binary.BigEndian, uint16(len(v)))
if err != nil {
return []byte{}, fmt.Errorf("cannot encode byte slice length: %v", err)
}
_, err = buf.Write(v)
if err != nil {
return []byte{}, fmt.Errorf("cannot encode byte slice: %v", err)
}
case time.Time:
err := binary.Write(buf, binary.BigEndian, uint64(v.Unix()))
if err != nil {
return []byte{}, fmt.Errorf("cannot encode time: %v", err)
}
default:
err := binary.Write(buf, binary.BigEndian, v)
if err != nil {
return []byte{}, fmt.Errorf("cannot encode: %v", err)
}
}
}
frame := buf.Bytes()
frame[0] = uint8(payloadType)
binary.BigEndian.PutUint16(frame[1:], uint16(len(frame)-3))
return frame, nil
}
func Decode(buf io.Reader) (any, error) {
var pTypeByte uint8
err := binary.Read(buf, binary.BigEndian, &pTypeByte)
if err != nil {
return nil, fmt.Errorf("cannot read payload type: %v", err)
}
pType := PayloadType(pTypeByte)
var pLen uint16
err = binary.Read(buf, binary.BigEndian, &pLen)
if err != nil {
return nil, fmt.Errorf("cannot read payload length: %v", err)
}
switch pType {
case PayloadHandshake:
return DecodeHandshake(buf)
case PayloadPing:
case PayloadPong:
case PayloadMessage:
case PayloadTest:
return DecodeTest(buf)
default:
return nil, fmt.Errorf("invalid payload type: %v", pType)
}
return pType, nil
}
func decodeNumeric(buf io.Reader, ptr any) error {
err := binary.Read(buf, binary.BigEndian, ptr)
if err != nil {
return fmt.Errorf("cannot decode: %v", err)
}
return nil
}
func decodeTime(buf io.Reader, ptr *time.Time) error {
var timeBuf uint64
err := binary.Read(buf, binary.BigEndian, &timeBuf)
if err != nil {
return fmt.Errorf("cannot decode time: %v", err)
}
*ptr = time.Unix(int64(timeBuf), 0)
return nil
}
func decodeBin(buf io.Reader, ptr *[]byte) error {
var payloadLen uint16
err := binary.Read(buf, binary.BigEndian, &payloadLen)
if err != nil {
return fmt.Errorf("cannot decode payload length: %v", err)
}
payload := make([]byte, payloadLen)
_, err = buf.Read(payload)
if err != nil {
return fmt.Errorf("cannot decode payload: %v", err)
}
*ptr = payload
return nil
}
func decodeString(buf io.Reader, ptr *string) error {
var strBytes []byte
err := decodeBin(buf, &strBytes)
if err != nil {
return err
}
*ptr = string(strBytes)
return nil
}
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