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packet.go
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packet.go
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package protocols
import (
"bytes"
"encoding/gob"
"fmt"
"io"
)
var (
Marshaller MarshallingProvider = gobMarshaller
)
type Code uint
type Packet struct {
Code Code
Val interface{}
SourceAddr Addr
}
func (packet *Packet) String() string {
return fmt.Sprintf("%v from %v", packet.Val, packet.SourceAddr)
}
type MarshallingProvider interface {
MarshalPacket(packet *Packet) ([]byte, error)
UnmarshalPacket([]byte, Protocol) (*Packet, error)
}
// ========================== gob Marshaller ==========================
var (
gobMarshaller *gobMarshallingProvider
)
type gobMarshallingProvider struct {
}
func (m *gobMarshallingProvider) MarshalPacket(packet *Packet) ([]byte, error) {
var buf bytes.Buffer
if err := m.encode(packet, &buf); err != nil {
return nil, err
}
return buf.Bytes(), nil
}
func (m *gobMarshallingProvider) UnmarshalPacket(buf []byte, protocol Protocol) (*Packet, error) {
return m.decode(bytes.NewReader(buf), protocol)
}
func (m *gobMarshallingProvider) safeEncode(enc *gob.Encoder, val interface{}) (err error) {
defer func() {
if r := recover(); r != nil {
err = fmt.Errorf("Panic encoding: %v", r)
}
}()
err = enc.Encode(val)
return
}
func (m *gobMarshallingProvider) encode(packet *Packet, writer io.Writer) error {
enc := gob.NewEncoder(writer)
err := m.safeEncode(enc, packet.Code)
if err != nil {
return fmt.Errorf("Error encoding status code %v: %v", packet.Code, err)
}
err = m.safeEncode(enc, packet.Val)
if err != nil {
return fmt.Errorf("Error encoding value for code %v: %v", packet.Code, err)
}
return nil
}
func (m *gobMarshallingProvider) decode(reader io.Reader, protocol Protocol) (*Packet, error) {
dec := gob.NewDecoder(reader)
var packet Packet
err := dec.Decode(&packet.Code)
if err != nil {
return nil, fmt.Errorf("Error decoding %v status code: %v", protocol.Name(), err)
}
// TODO move the gob-specific decoding here completely!
val, err := protocol.decodeValue(packet.Code, dec)
if err != nil {
return nil, err
}
packet.Val = val
return &packet, nil
}