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package packet
import (
"encoding/binary"
"encoding/json"
"fmt"
"io"
"github.com/vmihailenco/msgpack/v5"
"github.com/kyren223/eko/pkg/assert"
)
type Encoding uint8
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
}
}
const (
EncodingJson Encoding = iota
EncodingMsgPack
EncodingUnused1
EncodingUnused2
)
type PacketType uint8
func (t PacketType) String() string {
switch t {
case TypeEko:
return "PacketTypeEko"
case TypeError:
return "PacketTypeError"
default:
return fmt.Sprintf("PacketTypeInvalid(%v)", byte(t))
}
}
func (e PacketType) IsSupported() bool {
switch e {
case TypeEko, TypeError:
return true
default:
return false
}
}
const (
TypeEko PacketType = iota
TypeError
)
const (
VERSION = byte(1)
PACKET_MAX_SIZE = ^uint16(0)
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 {
io.Reader
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 {
data := make([]byte, PACKET_MAX_SIZE)
n, err := encoder.Read(data[HEADER_SIZE:])
assert.NoError(err, "packet encoder should never error when reading")
binary.BigEndian.PutUint16(data[LENGTH_OFFSET:], uint16(n))
data[VERSION_OFFSET] = VERSION
packetType, encoding := byte(encoder.Type()), byte(encoder.Encoding())
assert.Assert(packetType <= 63, "packet type exceeded allowed size type=%v", packetType)
assert.Assert(encoding <= 3, "encoding exceeded allowed permutations encoding=%v", encoding)
data[TYPE_OFFSET] = packetType | encoding<<6
return Packet{data[:HEADER_SIZE+n]}
}
func (p Packet) Version() uint8 {
return p.data[VERSION_OFFSET]
}
func (p Packet) Type() PacketType {
return PacketType(p.data[TYPE_OFFSET] & 63) // 2^6-1
}
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) String() string {
return fmt.Sprintf("{v%v %v %v %v: %v}", p.data[0], p.Encoding().String(), p.Type().String(), p.PayloadLength(), p.Payload())
}
// The payload data, caller must not modify the returned slice, even temporarily
func (p Packet) Payload() []byte {
return p.data[HEADER_SIZE:]
}
func (p Packet) DecodePayload(v TypedMessage) 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.Unreachable("encoding from packet should always be valid encoding=%v", p.Encoding())
return nil
}
}
func (p Packet) Into(writer io.Writer) error {
_, err := writer.Write(p.data[:len(p.data)])
return err
}
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