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packet.go
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packet.go
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package packet
import (
"bytes"
"compress/zlib"
"fmt"
"io"
"sync"
)
const MaxDataLength = 2097152
// Packet define a net data package
type Packet struct {
ID int32
Data []byte
}
// Marshal generate Packet with the ID and Fields
func Marshal(id int32, fields ...FieldEncoder) (pk Packet) {
var pb Builder
for _, v := range fields {
pb.WriteField(v)
}
return pb.Packet(id)
}
// Scan decode the packet and fill data into fields
func (p Packet) Scan(fields ...FieldDecoder) error {
r := bytes.NewReader(p.Data)
for _, v := range fields {
_, err := v.ReadFrom(r)
if err != nil {
return err
}
}
return nil
}
var bufPool = sync.Pool{
New: func() interface{} {
return new(bytes.Buffer)
},
}
// Pack 打包一个数据包
func (p *Packet) Pack(w io.Writer, threshold int) error {
if threshold >= 0 {
return p.packWithCompression(w, threshold)
} else {
return p.packWithoutCompression(w)
}
}
func (p *Packet) packWithoutCompression(w io.Writer) error {
buffer := bufPool.Get().(*bytes.Buffer)
defer bufPool.Put(buffer)
buffer.Reset()
n, err := VarInt(p.ID).WriteTo(buffer)
if err != nil {
panic(err)
}
// Length
_, err = VarInt(int(n) + len(p.Data)).WriteTo(w)
if err != nil {
return err
}
// Packet ID
_, err = buffer.WriteTo(w)
if err != nil {
return err
}
// Data
_, err = w.Write(p.Data)
if err != nil {
return err
}
return nil
}
func (p *Packet) packWithCompression(w io.Writer, threshold int) error {
buff := bufPool.Get().(*bytes.Buffer)
defer bufPool.Put(buff)
buff.Reset()
if len(p.Data) < threshold {
_, err := VarInt(0).WriteTo(buff)
if err != nil {
return err
}
_, err = VarInt(p.ID).WriteTo(buff)
if err != nil {
return err
}
_, err = buff.Write(p.Data)
if err != nil {
return err
}
// Packet Length
_, err = VarInt(buff.Len()).WriteTo(w)
if err != nil {
return err
}
// Data Length + Packet ID + Data
_, err = buff.WriteTo(w)
if err != nil {
return err
}
} else {
zw := zlib.NewWriter(buff)
n1, err := VarInt(p.ID).WriteTo(zw)
if err != nil {
return err
}
n2, err := zw.Write(p.Data)
if err != nil {
return err
}
err = zw.Close()
if err != nil {
return err
}
dataLength := bufPool.Get().(*bytes.Buffer)
defer bufPool.Put(dataLength)
dataLength.Reset()
n3, err := VarInt(int(n1) + n2).WriteTo(dataLength)
if err != nil {
return err
}
// Packet Length
_, err = VarInt(int(n3) + buff.Len()).WriteTo(w)
if err != nil {
return err
}
// Data Length
_, err = dataLength.WriteTo(w)
if err != nil {
return err
}
// PacketID + Data
_, err = buff.WriteTo(w)
if err != nil {
return err
}
}
return nil
}
// UnPack in-place decompression a packet
func (p *Packet) UnPack(r io.Reader, threshold int) error {
if threshold >= 0 {
return p.unpackWithCompression(r, threshold)
} else {
return p.unpackWithoutCompression(r)
}
}
func (p *Packet) unpackWithoutCompression(r io.Reader) error {
var Length VarInt
_, err := Length.ReadFrom(r)
if err != nil {
return err
}
var PacketID VarInt
n, err := PacketID.ReadFrom(r)
if err != nil {
return err
}
p.ID = int32(PacketID)
lengthOfData := int(Length) - int(n)
if lengthOfData < 0 || lengthOfData > MaxDataLength {
return fmt.Errorf("uncompressed packet error: lenght is %d", lengthOfData)
}
if cap(p.Data) < lengthOfData {
p.Data = make([]byte, lengthOfData)
} else {
p.Data = p.Data[:lengthOfData]
}
_, err = io.ReadFull(r, p.Data)
if err != nil {
return err
}
return nil
}
func (p *Packet) unpackWithCompression(r io.Reader, threshold int) error {
var PacketLength VarInt
_, err := PacketLength.ReadFrom(r)
if err != nil {
return err
}
buff := bufPool.Get().(*bytes.Buffer)
defer bufPool.Put(buff)
buff.Reset()
_, err = io.CopyN(buff, r, int64(PacketLength))
if err != nil {
return err
}
r = bytes.NewReader(buff.Bytes())
var DataLength VarInt
n2, err := DataLength.ReadFrom(r)
if err != nil {
return err
}
var PacketID VarInt
if DataLength != 0 {
if int(DataLength) < threshold {
return fmt.Errorf("compressed packet error: size of %d is below threshold of %d", DataLength, threshold)
}
if DataLength > MaxDataLength {
return fmt.Errorf("compressed packet error: size of %d is larger than protocol maximum of %d", DataLength, MaxDataLength)
}
zr, err := zlib.NewReader(r)
if err != nil {
return err
}
defer zr.Close()
r = zr
n3, err := PacketID.ReadFrom(r)
if err != nil {
return err
}
DataLength -= VarInt(n3)
} else {
n3, err := PacketID.ReadFrom(r)
if err != nil {
return err
}
DataLength = VarInt(int64(PacketLength) - n2 - n3)
}
if cap(p.Data) < int(DataLength) {
p.Data = make([]byte, DataLength)
} else {
p.Data = p.Data[:DataLength]
}
p.ID = int32(PacketID)
_, err = io.ReadFull(r, p.Data)
if err != nil {
return err
}
return nil
}