go-ricochet/utils/networking.go

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package utils
import (
"encoding/binary"
"errors"
"net"
"strconv"
)
// RicochetData is a structure containing the raw data and the channel it the
// message originated on.
type RicochetData struct {
Channel int32
Data []byte
}
// RicochetNetworkInterface abstract operations that interact with ricochet's
// packet layer.
type RicochetNetworkInterface interface {
Recv(conn net.Conn) ([]byte, error)
SendRicochetPacket(conn net.Conn, channel int32, data []byte)
RecvRicochetPackets(conn net.Conn) ([]RicochetData, error)
}
// RicochetNetwork is a concrete implementation of the RicochetNetworkInterface
type RicochetNetwork struct {
}
// Recv reads data from the client, and returns the raw byte array, else error.
func (rn *RicochetNetwork) Recv(conn net.Conn) ([]byte, error) {
buf := make([]byte, 4096)
n, err := conn.Read(buf)
if err != nil {
return nil, err
}
ret := make([]byte, n)
copy(ret[:], buf[:])
return ret, nil
}
// SendRicochetPacket places the data into a structure needed for the client to
// decode the packet and writes the packet to the network.
func (rn *RicochetNetwork) SendRicochetPacket(conn net.Conn, channel int32, data []byte) {
header := make([]byte, 4+len(data))
header[0] = byte(len(header) >> 8)
header[1] = byte(len(header) & 0x00FF)
header[2] = 0x00
header[3] = byte(channel)
copy(header[4:], data[:])
conn.Write(header)
}
// RecvRicochetPackets returns an array of new messages received from the ricochet client
func (rn *RicochetNetwork) RecvRicochetPackets(conn net.Conn) ([]RicochetData, error) {
buf, err := rn.Recv(conn)
if err != nil && len(buf) < 4 {
return nil, errors.New("failed to retrieve new messages from the client")
}
pos := 0
finished := false
var datas []RicochetData
for !finished {
size := int(binary.BigEndian.Uint16(buf[pos+0 : pos+2]))
channel := int(binary.BigEndian.Uint16(buf[pos+2 : pos+4]))
if size < 4 {
return datas, errors.New("invalid ricochet packet received (size=" + strconv.Itoa(size) + ")")
}
if pos+size > len(buf) {
return datas, errors.New("partial data packet received")
}
data := RicochetData{}
data.Channel = int32(channel)
if pos+4 >= len(buf) {
data.Data = make([]byte, 0)
} else {
data.Data = buf[pos+4 : pos+size]
}
datas = append(datas, data)
pos += size
if pos >= len(buf) {
finished = true
}
}
return datas, nil
}