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nnet/packet/packer.go

124 lines
2.3 KiB
Go

package packet
import (
"bytes"
"errors"
)
var _ Packer = (*DefaultPacker)(nil)
type DefaultPacker struct {
buf *bytes.Buffer
size int // 最近一次 长度
typ byte // 最近一次 数据帧类型
}
// Codec constants.
const (
headLength = 4
maxPacketSize = 64 * 1024
)
var ErrPacketSizeExceed = errors.New("codec: packet size exceed")
func NewDefaultPacker() Packer {
return &DefaultPacker{
buf: bytes.NewBuffer(nil),
size: -1,
}
}
func (d *DefaultPacker) Pack(typ Type, data []byte) ([]byte, error) {
if typ < Handshake || typ > Kick {
return nil, ErrWrongPacketType
}
p := &Packet{Type: typ, Length: uint32(len(data))}
buf := make([]byte, p.Length+headLength)
// header
buf[0] = byte(p.Type)
copy(buf[1:headLength], d.intToBytes(p.Length))
// body
copy(buf[headLength:], data)
return buf, nil
}
// Encode packet data length to bytes(Big end)
func (d *DefaultPacker) intToBytes(n uint32) []byte {
buf := make([]byte, 3)
buf[0] = byte((n >> 16) & 0xFF)
buf[1] = byte((n >> 8) & 0xFF)
buf[2] = byte(n & 0xFF)
return buf
}
func (d *DefaultPacker) Unpack(data []byte) ([]interface{}, error) {
d.buf.Write(data) // copy
var (
packets []interface{}
err error
)
// 检查包长度
if d.buf.Len() < headLength {
return nil, err
}
// 第一次拆包
if d.size < 0 {
if err = d.readHeader(); err != nil {
return nil, err
}
}
for d.size <= d.buf.Len() {
// 读取
p := &Packet{
Type: Type(d.typ),
Length: uint32(d.size),
Data: d.buf.Next(d.size),
}
packets = append(packets, p)
// 剩余数据不满足至少一个数据帧,重置数据帧长度
// 数据缓存内存 保留至 下一次进入本方法以继续拆包
if d.buf.Len() < headLength {
d.size = -1
break
}
// 读取下一个包 next
if err = d.readHeader(); err != nil {
return packets, err
}
}
return packets, nil
}
func (d *DefaultPacker) readHeader() error {
header := d.buf.Next(headLength)
d.typ = header[0]
if d.typ < Handshake || d.typ > Kick {
return ErrWrongPacketType
}
d.size = d.bytesToInt(header[1:])
// 最大包限定
if d.size > maxPacketSize {
return ErrPacketSizeExceed
}
return nil
}
// Decode packet data length byte to int(Big end)
func (d *DefaultPacker) bytesToInt(b []byte) int {
result := 0
for _, v := range b {
result = result<<8 + int(v)
}
return result
}