forked from lonng/nano
/
codec.go
147 lines (123 loc) · 3.79 KB
/
codec.go
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// Copyright (c) nano Author. All Rights Reserved.
//
// Permission is hereby granted, free of charge, to any person obtaining a copy
// of this software and associated documentation files (the "Software"), to deal
// in the Software without restriction, including without limitation the rights
// to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
// copies of the Software, and to permit persons to whom the Software is
// furnished to do so, subject to the following conditions:
//
// The above copyright notice and this permission notice shall be included in all
// copies or substantial portions of the Software.
//
// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
// IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
// FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
// AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
// LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
// OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
// SOFTWARE.
package codec
import (
"bytes"
"errors"
"github.com/lonnng/nano/internal/packet"
)
// Codec constants.
const (
HeadLength = 4
MaxPacketSize = 64 * 1024
)
// ErrPacketSizeExcced is the error used for encode/decode.
var ErrPacketSizeExcced = errors.New("codec: packet size exceed")
// A Decoder reads and decodes network data slice
type Decoder struct {
buf *bytes.Buffer
size int // last packet length
typ byte // last packet type
}
// NewDecoder returns a new decoder that used for decode network bytes slice.
func NewDecoder() *Decoder {
return &Decoder{
buf: bytes.NewBuffer(nil),
size: -1,
}
}
func (c *Decoder) forward() error {
header := c.buf.Next(HeadLength)
c.typ = header[0]
if c.typ < packet.Handshake || c.typ > packet.Kick {
return packet.ErrWrongPacketType
}
c.size = bytesToInt(header[1:])
// packet length limitation
if c.size > MaxPacketSize {
return ErrPacketSizeExcced
}
return nil
}
// Decode decode the network bytes slice to packet.Packet(s)
// TODO(Warning): shared slice
func (c *Decoder) Decode(data []byte) ([]*packet.Packet, error) {
c.buf.Write(data)
var (
packets []*packet.Packet
err error
)
// check length
if c.buf.Len() < HeadLength {
return nil, err
}
// first time
if c.size < 0 {
if err = c.forward(); err != nil {
return nil, err
}
}
for c.size <= c.buf.Len() {
p := &packet.Packet{Type: packet.Type(c.typ), Length: c.size, Data: c.buf.Next(c.size)}
packets = append(packets, p)
// more packet
if c.buf.Len() < HeadLength {
c.size = -1
break
}
if err = c.forward(); err != nil {
return nil, err
}
}
return packets, nil
}
// Encode create a packet.Packet from the raw bytes slice and then encode to network bytes slice
// Protocol refs: https://github.com/NetEase/pomelo/wiki/Communication-Protocol
//
// -<type>-|--------<length>--------|-<data>-
// --------|------------------------|--------
// 1 byte packet type, 3 bytes packet data length(big end), and data segment
func Encode(typ packet.Type, data []byte) ([]byte, error) {
if typ < packet.Handshake || typ > packet.Kick {
return nil, packet.ErrWrongPacketType
}
p := &packet.Packet{Type: typ, Length: len(data)}
buf := make([]byte, p.Length+HeadLength)
buf[0] = byte(p.Type)
copy(buf[1:HeadLength], intToBytes(p.Length))
copy(buf[HeadLength:], data)
return buf, nil
}
// Decode packet data length byte to int(Big end)
func bytesToInt(b []byte) int {
result := 0
for _, v := range b {
result = result<<8 + int(v)
}
return result
}
// Encode packet data length to bytes(Big end)
func intToBytes(n int) []byte {
buf := make([]byte, 3)
buf[0] = byte((n >> 16) & 0xFF)
buf[1] = byte((n >> 8) & 0xFF)
buf[2] = byte(n & 0xFF)
return buf
}