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Fix ReadPacket and WritePacket payload length is a multiple #209

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Fix ReadPacket and WritePacket payload length is a multiple #209

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Fix ReadPacket and WritePacket payload length is a multiple
michaelyou Dec 12, 2017
081bc42
Merge branch 'master' into fix-message-payload-length-equals-maxpaylo…
michaelyou May 22, 2018
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152 changes: 57 additions & 95 deletions packet/conn.go
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Original file line number Diff line number Diff line change
Expand Up @@ -2,7 +2,6 @@ package packet

import (
"bufio"
"bytes"
"io"
"net"

Expand Down Expand Up @@ -30,124 +29,87 @@ func NewConn(conn net.Conn) *Conn {
}

func (c *Conn) ReadPacket() ([]byte, error) {
var buf bytes.Buffer

if err := c.ReadPacketTo(&buf); err != nil {
return nil, errors.Trace(err)
} else {
return buf.Bytes(), nil
}

// header := []byte{0, 0, 0, 0}

// if _, err := io.ReadFull(c.br, header); err != nil {
// return nil, ErrBadConn
// }

// length := int(uint32(header[0]) | uint32(header[1])<<8 | uint32(header[2])<<16)
// if length < 1 {
// return nil, fmt.Errorf("invalid payload length %d", length)
// }

// sequence := uint8(header[3])

// if sequence != c.Sequence {
// return nil, fmt.Errorf("invalid sequence %d != %d", sequence, c.Sequence)
// }

// c.Sequence++

// data := make([]byte, length)
// if _, err := io.ReadFull(c.br, data); err != nil {
// return nil, ErrBadConn
// } else {
// if length < MaxPayloadLen {
// return data, nil
// }

// var buf []byte
// buf, err = c.ReadPacket()
// if err != nil {
// return nil, ErrBadConn
// } else {
// return append(data, buf...), nil
// }
// }
}

func (c *Conn) ReadPacketTo(w io.Writer) error {
header := []byte{0, 0, 0, 0}

if _, err := io.ReadFull(c.br, header); err != nil {
return ErrBadConn
}
var prevData []byte
for {
// read packet header
header := []byte{0, 0, 0, 0}
if _, err := io.ReadFull(c.br, header); err != nil {
return nil, ErrBadConn
}

length := int(uint32(header[0]) | uint32(header[1])<<8 | uint32(header[2])<<16)
if length < 1 {
return errors.Errorf("invalid payload length %d", length)
}
// packet length [24 bit]
length := int(uint32(header[0]) | uint32(header[1])<<8 | uint32(header[2])<<16)
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Why not checking length with max payload length here?


sequence := uint8(header[3])
// check packet sync [8 bit]
sequence := uint8(header[3])
if sequence != c.Sequence {
return nil, errors.Errorf("invalid sequence %d != %d", sequence, c.Sequence)
}
c.Sequence++

if sequence != c.Sequence {
return errors.Errorf("invalid sequence %d != %d", sequence, c.Sequence)
}
// packets with length 0 terminate a previous packet which is a
// multiple of (2^24)−1 bytes long
if length == 0 {
// there was no previous packet
if prevData == nil {
return nil, errors.Errorf("invalid payload length %d", length)
}
return prevData, nil
}

c.Sequence++
// read packet body [length bytes]
data := make([]byte, length)
if _, err := io.ReadFull(c.br, data); err != nil {
return nil, ErrBadConn
}

if n, err := io.CopyN(w, c.br, int64(length)); err != nil {
return ErrBadConn
} else if n != int64(length) {
return ErrBadConn
} else {
// return data if this was the last packet
if length < MaxPayloadLen {
return nil
}
// zero allocations for non-split packets
if prevData == nil {
return data, nil
}

if err := c.ReadPacketTo(w); err != nil {
return err
return append(prevData, data...), nil
}
prevData = append(prevData, data...)
}

return nil
}

// data already has 4 bytes header
// will modify data inplace
func (c *Conn) WritePacket(data []byte) error {
length := len(data) - 4

for length >= MaxPayloadLen {
data[0] = 0xff
data[1] = 0xff
data[2] = 0xff

for {
var size int
if length >= MaxPayloadLen {
data[0] = 0xff
data[1] = 0xff
data[2] = 0xff
size = MaxPayloadLen
} else {
data[0] = byte(length)
data[1] = byte(length >> 8)
data[2] = byte(length >> 16)
size = length
}
data[3] = c.Sequence

if n, err := c.Write(data[:4+MaxPayloadLen]); err != nil {
if n, err := c.Write(data[:4+size]); err != nil {
return ErrBadConn
} else if n != (4 + MaxPayloadLen) {
} else if n != (4 + size) {
return ErrBadConn
} else {
c.Sequence++
length -= MaxPayloadLen
data = data[MaxPayloadLen:]
if size != MaxPayloadLen {
return nil
}
length -= size
data = data[size:]
continue
}
}

data[0] = byte(length)
data[1] = byte(length >> 8)
data[2] = byte(length >> 16)
data[3] = c.Sequence

if n, err := c.Write(data); err != nil {
return ErrBadConn
} else if n != len(data) {
return ErrBadConn
} else {
c.Sequence++
return nil
}
}

func (c *Conn) ResetSequence() {
Expand Down