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package packet
import (
"context"
"encoding/binary"
"encoding/json"
"errors"
"fmt"
"io"
"math"
"github.com/vmihailenco/msgpack/v5"
"github.com/kyren223/eko/pkg/assert"
)
type Encoding uint8
const (
EncodingJson Encoding = iota
EncodingMsgPack
EncodingUnused1
EncodingUnused2
)
func (e Encoding) String() string {
switch e {
case EncodingJson:
return "EncodingJson"
case EncodingMsgPack:
return "EncodingMsgPack"
case EncodingUnused1:
return "EncodingUnused1"
case EncodingUnused2:
return "EncodingUnused2"
default:
return fmt.Sprintf("EncodingInvalid(%v)", byte(e))
}
}
func (e Encoding) IsSupported() bool {
switch e {
case EncodingJson, EncodingMsgPack:
return true
default:
return false
}
}
type PacketType uint8
const (
PacketError PacketType = iota
PacketSendMessage
PacketMessages
)
func (t PacketType) String() string {
switch t {
case PacketError:
return "PacketError"
case PacketSendMessage:
return "PacketSendMessage"
case PacketMessages:
return "PacketMessages"
default:
return fmt.Sprintf("PacketInvalidType(%v)", byte(t))
}
}
func (e PacketType) IsSupported() bool {
switch e {
case PacketError, PacketSendMessage, PacketMessages:
return true
default:
return false
}
}
// True for all packets that a server may push passively to the client.
func (e PacketType) IsPush() bool {
switch e {
case PacketError, PacketSendMessage:
return false
default:
return true
}
}
const (
VERSION = byte(1)
PACKET_MAX_SIZE = math.MaxUint16
PAYLOAD_MAX_SIZE = PACKET_MAX_SIZE - HEADER_SIZE
HEADER_SIZE = 4
VERSION_OFFSET = 0
TYPE_OFFSET = 1
ENCODING_OFFSET = 1
LENGTH_OFFSET = 2
)
type PacketEncoder interface {
Payload() []byte
Encoding() Encoding
Type() PacketType
}
// The following diagram shows the packet structure:
//
// 0 1 2 3
// 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
// +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
// | Version |En.| Type | Payload Length |
// +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
// | Payload... Payload Length bytes ... |
// +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
type Packet struct {
data []byte
}
func NewPacket(encoder PacketEncoder) Packet {
payload := encoder.Payload()
n := len(payload)
assert.Assert(0 <= n && n <= PAYLOAD_MAX_SIZE, "size of payload must be valid", "size", n)
data := make([]byte, HEADER_SIZE+n)
data[VERSION_OFFSET] = VERSION
packetType, encoding := byte(encoder.Type()), byte(encoder.Encoding())
assert.Assert(packetType <= 63, "packet type exceeded allowed size", "type", packetType)
assert.Assert(encoding <= 3, "encoding exceeded allowed size", "encoding", encoding)
data[TYPE_OFFSET] = packetType | encoding<<6
binary.BigEndian.PutUint16(data[LENGTH_OFFSET:], uint16(n))
copy(data[HEADER_SIZE:], payload)
return Packet{data}
}
func (p Packet) Version() uint8 {
return p.data[VERSION_OFFSET]
}
func (p Packet) Type() PacketType {
return PacketType(p.data[TYPE_OFFSET] & 63)
}
func (p Packet) Encoding() Encoding {
return Encoding(p.data[ENCODING_OFFSET] >> 6)
}
func (p Packet) PayloadLength() uint16 {
return binary.BigEndian.Uint16(p.data[LENGTH_OFFSET:])
}
func (p Packet) Payload() []byte {
return p.data[HEADER_SIZE:]
}
func (p Packet) String() string {
return fmt.Sprintf("Packet(v%v %v %v [%v bytes...])", p.Version(), p.Encoding().String(), p.Type().String(), p.PayloadLength())
}
func (p Packet) Into(writer io.Writer) (int, error) {
return writer.Write(p.data)
}
func (p Packet) DecodePayloadInto(v Payload) error {
if p.Type() != v.Type() {
return fmt.Errorf("type mismatch: want %v got %v", p.Type(), v.Type())
}
switch p.Encoding() {
case EncodingJson:
return json.Unmarshal(p.Payload(), v)
case EncodingMsgPack:
return msgpack.Unmarshal(p.Payload(), v)
case EncodingUnused1:
fallthrough
case EncodingUnused2:
return fmt.Errorf("unsupported encoding: %v", p.Encoding().String())
default:
assert.Never("encoding from packet should always be valid", "encoding", p.Encoding())
return nil
}
}
func (p Packet) DecodedPayload() (Payload, error) {
var payload Payload
switch p.Type() {
case PacketError:
payload = &ErrorMessage{}
case PacketMessages:
payload = &Messages{}
case PacketSendMessage:
payload = &SendMessage{}
default:
assert.Never("packet type of a packet struct must always be valid")
}
err := p.DecodePayloadInto(payload)
return payload, err
}
var (
PacketUnsupportedVersion error = errors.New("packet error: unsupported version")
PacketUnsupportedEncoding error = errors.New("packet error: unsupported encoding")
PacketUnsupportedType error = errors.New("packet error: unsupported type")
)
type PacketFramer struct {
buffer []byte
Out chan Packet
}
func NewFramer(ctx context.Context) PacketFramer {
return PacketFramer{
Out: make(chan Packet, 10),
}
}
func (f *PacketFramer) Push(ctx context.Context, data []byte) error {
f.buffer = append(f.buffer, data...)
for {
packet, err := f.parse()
if packet == nil || err != nil {
return err
}
select {
case f.Out <- *packet:
case <-ctx.Done():
return ctx.Err()
}
}
}
func (f *PacketFramer) parse() (*Packet, error) {
if len(f.buffer) < HEADER_SIZE {
return nil, nil
}
if f.buffer[VERSION_OFFSET] != VERSION {
return nil, PacketUnsupportedVersion
}
encoding := Encoding(f.buffer[ENCODING_OFFSET] >> 6)
if !encoding.IsSupported() {
return nil, PacketUnsupportedEncoding
}
packetType := PacketType(f.buffer[TYPE_OFFSET] & 63)
if !packetType.IsSupported() {
return nil, PacketUnsupportedType
}
length := binary.BigEndian.Uint16(f.buffer[LENGTH_OFFSET:])
if len(f.buffer)-HEADER_SIZE < int(length) {
// Wait for more data to arrive
return nil, nil
}
fullLength := HEADER_SIZE + length
packetBuffer := make([]byte, fullLength)
copy(packetBuffer, f.buffer[:fullLength])
copy(f.buffer, f.buffer[fullLength:])
f.buffer = f.buffer[:len(f.buffer)-int(fullLength)]
return &Packet{packetBuffer}, nil
}
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