gopenfusion/protocol/packet.go
CPunch 850dd59967 protocol/packet: accept structs by value for encoding
- server/loginServer: no longer sending packets by pointer, except in cases like AcceptLogin(), which operates on a sent structure slice. since these are already allocated, no need to copy them
2023-03-11 00:24:20 -06:00

159 lines
3.5 KiB
Go

package protocol
import (
"encoding/binary"
"fmt"
"io"
"reflect"
"strconv"
"unicode/utf16"
)
/*
this file handles serializing (and deserializing) structs to alignment-strict c structures generated via `tools/genstructs.py`.
see script for details on usage!
*/
type Packet struct {
readWriter io.ReadWriter
}
func NewPacket(readWriter io.ReadWriter) Packet {
return Packet{
readWriter: readWriter,
}
}
func (pkt Packet) encodeStructField(field reflect.StructField, value reflect.Value) error {
// log.Printf("Encoding '%s'", field.Name)
switch field.Type.Kind() {
case reflect.String: // all strings in fusionfall packets are encoded as utf16, we'll need to encode it
sz, err := strconv.Atoi(field.Tag.Get("size"))
if err != nil {
return fmt.Errorf("Failed to grab string 'size' tag!!")
}
buf16 := utf16.Encode([]rune(value.String()))
// len(buf16) needs to be the same size as sz
if len(buf16) > sz {
// truncate
buf16 = buf16[:sz]
} else {
// grow
// TODO: probably a better way to do this?
for len(buf16) < sz {
buf16 = append(buf16, 0)
}
}
// write
if err := binary.Write(pkt.readWriter, binary.LittleEndian, buf16); err != nil {
return err
}
default:
if err := pkt.Encode(value.Interface()); err != nil {
return err
}
}
// write padding bytes
pad, err := strconv.Atoi(field.Tag.Get("pad"))
if err == nil {
for i := 0; i < pad; i++ {
if _, err := pkt.readWriter.Write([]byte{0}); err != nil {
return err
}
}
}
return nil
}
func (pkt Packet) Encode(data interface{}) error {
rv := reflect.Indirect(reflect.ValueOf(data))
switch rv.Kind() {
case reflect.Struct:
// walk through each struct fields
sz := rv.NumField()
for i := 0; i < sz; i++ {
if err := pkt.encodeStructField(rv.Type().Field(i), rv.Field(i)); err != nil {
return err
}
}
default:
// we pass everything else to go's binary package
if err := binary.Write(pkt.readWriter, binary.LittleEndian, data); err != nil {
return err
}
}
return nil
}
func (pkt Packet) decodeStructField(field reflect.StructField, value reflect.Value) error {
// log.Printf("Decoding '%s'", field.Name)
switch field.Type.Kind() {
case reflect.String: // all strings in fusionfall packets are encoded as utf16, we'll need to decode it
sz, err := strconv.Atoi(field.Tag.Get("size"))
if err != nil {
return fmt.Errorf("Failed to grab string 'size' tag!!")
}
buf16 := make([]uint16, sz)
if err := binary.Read(pkt.readWriter, binary.LittleEndian, buf16); err != nil {
return err
}
// find null terminator
var realSize int
for ; realSize < len(buf16); realSize++ {
if buf16[realSize] == 0 {
break
}
}
value.SetString(string(utf16.Decode(buf16[:realSize])))
default:
if err := pkt.Decode(value.Addr().Interface()); err != nil {
return err
}
}
// consume padding bytes
pad, err := strconv.Atoi(field.Tag.Get("pad"))
if err == nil {
for i := 0; i < pad; i++ {
if _, err := pkt.readWriter.Read([]byte{0}); err != nil {
return err
}
}
}
return nil
}
func (pkt Packet) Decode(data interface{}) error {
rv := reflect.Indirect(reflect.ValueOf(data))
switch rv.Kind() {
case reflect.Struct:
// walk through each struct fields
sz := rv.NumField()
for i := 0; i < sz; i++ {
if err := pkt.decodeStructField(rv.Type().Field(i), rv.Field(i)); err != nil {
return err
}
}
default:
if err := binary.Read(pkt.readWriter, binary.LittleEndian, data); err != nil {
return err
}
}
return nil
}