gopenfusion/protocol/packet.go
2023-03-09 16:42:13 -06:00

239 lines
5.5 KiB
Go

package protocol
import (
"encoding/binary"
"fmt"
"reflect"
"strconv"
"unicode/utf16"
"unsafe"
)
/*
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 {
ByteOrder binary.ByteOrder
Buf []byte
cursor int // to keep track of things like member alignment for easier debugging
}
const PACK_ALIGN = 4
func NewPacket(buf []byte) *Packet {
pkt := &Packet{
ByteOrder: binary.LittleEndian,
Buf: buf,
cursor: 0,
}
return pkt
}
func (pkt *Packet) ResetCursor() {
pkt.cursor = 0
}
func (pkt *Packet) writeRaw(data []byte) {
pkt.Buf = append(pkt.Buf, data...)
pkt.cursor += len(data)
}
func (pkt *Packet) Write(data []byte) {
pkt.writeRaw(data)
if len(pkt.Buf) > CN_PACKET_BUFFER_SIZE {
panic(fmt.Errorf("Failed to write to packet, invalid size!"))
}
}
func (pkt *Packet) writeByte(data byte) {
pkt.Write([]byte{data})
}
func (pkt *Packet) readRaw(sz int) []byte {
data := pkt.Buf[:sz]
pkt.Buf = pkt.Buf[sz:]
pkt.cursor += sz
return data
}
func (pkt *Packet) Read(sz int) []byte {
if sz > len(pkt.Buf) {
panic(fmt.Errorf("Failed to read from packet, invalid size!"))
}
return pkt.readRaw(sz)
}
func (pkt *Packet) readByte() byte {
return pkt.Read(1)[0]
}
func (pkt *Packet) encodeStructField(field reflect.StructField, value reflect.Value) {
// log.Printf("Encoding '%s', current cursor: %d", field.Name, len(pkt.Buf))
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 {
panic(fmt.Errorf("Failed to grab string 'size' tag!!"))
}
sz *= 2
buf16 := utf16.Encode([]rune(value.String()))
buf := *(*[]byte)(unsafe.Pointer(&buf16))
// len(buf) needs to be the same size as sz
if len(buf) > sz {
// truncate
buf = buf[:sz]
} else {
// grow
for len(buf) < sz {
buf = append(buf, 0)
}
}
pkt.Write(buf)
default:
pkt.Encode(value.Addr().Interface())
}
// write padding bytes
pad, err := strconv.Atoi(field.Tag.Get("pad"))
if err == nil {
for i := 0; i < pad; i++ {
pkt.writeByte(0)
}
}
}
func (pkt *Packet) Encode(data interface{}) {
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++ {
pkt.encodeStructField(rv.Type().Field(i), rv.Field(i))
}
case reflect.Array:
sz := rv.Len()
// encode data
for i := 0; i < sz; i++ {
elem := rv.Index(i)
pkt.Encode(elem.Addr().Interface())
}
case reflect.Uint8:
pkt.writeByte(byte(rv.Uint()))
case reflect.Uint16:
tmp := make([]byte, 2)
pkt.ByteOrder.PutUint16(tmp, uint16(rv.Uint()))
pkt.Write(tmp)
case reflect.Uint32:
tmp := make([]byte, 4)
pkt.ByteOrder.PutUint32(tmp, uint32(rv.Uint()))
pkt.Write(tmp)
case reflect.Uint64:
tmp := make([]byte, 8)
pkt.ByteOrder.PutUint64(tmp, uint64(rv.Uint()))
pkt.Write(tmp)
// im using the PutUintX() api here because it's functionally the same and apparently PutIntX doesn't exist?
case reflect.Int8:
pkt.writeByte(byte(rv.Int()))
case reflect.Int16:
tmp := make([]byte, 2)
pkt.ByteOrder.PutUint16(tmp, uint16(rv.Int()))
pkt.Write(tmp)
case reflect.Int32:
tmp := make([]byte, 4)
pkt.ByteOrder.PutUint32(tmp, uint32(rv.Int()))
pkt.Write(tmp)
case reflect.Int64:
tmp := make([]byte, 8)
pkt.ByteOrder.PutUint64(tmp, uint64(rv.Int()))
pkt.Write(tmp)
}
}
func (pkt *Packet) decodeStructField(field reflect.StructField, value reflect.Value) {
// log.Printf("Decoding '%s', current cursor: %d", field.Name, pkt.cursor)
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 {
panic(fmt.Errorf("Failed to grab string 'size' tag!!"))
}
// sz * sizeof(char16_t)
sz *= 2
buf := make([]byte, 0, sz)
buf = append(buf, pkt.Read(sz)...)
buf16 := *(*[]uint16)(unsafe.Pointer(&buf))
// find null terminator
var realSize int
for ; realSize < len(buf16); realSize++ {
if buf16[realSize] == 0 {
break
}
}
str := string(utf16.Decode(buf16[:realSize]))
value.SetString(str)
default:
pkt.Decode(value.Addr().Interface())
}
// read padding bytes
pad, err := strconv.Atoi(field.Tag.Get("pad"))
if err == nil {
for i := 0; i < pad; i++ {
pkt.readByte()
}
}
}
func (pkt *Packet) Decode(data interface{}) {
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++ {
pkt.decodeStructField(rv.Type().Field(i), rv.Field(i))
}
case reflect.Array:
sz := rv.Len()
// decode data
for i := 0; i < sz; i++ {
elem := rv.Index(i)
pkt.Decode(elem.Addr().Interface())
}
case reflect.Uint8:
rv.SetUint(uint64(pkt.readByte()))
case reflect.Uint16:
rv.SetUint(uint64(pkt.ByteOrder.Uint16(pkt.Read(2))))
case reflect.Uint32:
rv.SetUint(uint64(pkt.ByteOrder.Uint32(pkt.Read(4))))
case reflect.Uint64:
rv.SetUint(pkt.ByteOrder.Uint64(pkt.Read(8)))
case reflect.Int8:
rv.SetInt(int64(pkt.readByte()))
case reflect.Int16:
rv.SetInt(int64(pkt.ByteOrder.Uint16(pkt.Read(2))))
case reflect.Int32:
rv.SetInt(int64(pkt.ByteOrder.Uint32(pkt.Read(4))))
case reflect.Int64:
rv.SetInt(int64(pkt.ByteOrder.Uint64(pkt.Read(8))))
}
}