go-ricochet/utils/networking.go

83 lines
2.2 KiB
Go

package utils
import (
"bytes"
"encoding/binary"
"errors"
"io"
)
// RicochetData is a structure containing the raw data and the channel it the
// message originated on.
type RicochetData struct {
Channel int32
Data []byte
}
//Equals compares a RicochetData object to another and returns true if contain
// the same data.
func (rd RicochetData) Equals(other RicochetData) bool {
return rd.Channel == other.Channel && bytes.Equal(rd.Data, other.Data)
}
// RicochetNetworkInterface abstract operations that interact with ricochet's
// packet layer.
type RicochetNetworkInterface interface {
SendRicochetPacket(dst io.Writer, channel int32, data []byte) error
RecvRicochetPacket(reader io.Reader) (RicochetData, error)
}
// RicochetNetwork is a concrete implementation of the RicochetNetworkInterface
type RicochetNetwork struct {
}
// 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(dst io.Writer, channel int32, data []byte) error {
packet := make([]byte, 4+len(data))
if len(packet) > 65535 {
return errors.New("packet too large")
}
binary.BigEndian.PutUint16(packet[0:2], uint16(len(packet)))
if channel < 0 || channel > 65535 {
return errors.New("invalid channel ID")
}
binary.BigEndian.PutUint16(packet[2:4], uint16(channel))
copy(packet[4:], data[:])
for pos := 0; pos < len(packet); {
n, err := dst.Write(packet[pos:])
if err != nil {
return err
}
pos += n
}
return nil
}
// RecvRicochetPacket returns the next packet from reader as a RicochetData
// structure, or an error.
func (rn *RicochetNetwork) RecvRicochetPacket(reader io.Reader) (RicochetData, error) {
packet := RicochetData{}
// Read the four-byte header to get packet length
header := make([]byte, 4)
if _, err := io.ReadAtLeast(reader, header, len(header)); err != nil {
return packet, err
}
size := int(binary.BigEndian.Uint16(header[0:2]))
if size < 4 {
return packet, errors.New("invalid packet length")
}
packet.Channel = int32(binary.BigEndian.Uint16(header[2:4]))
packet.Data = make([]byte, size-4)
if _, err := io.ReadAtLeast(reader, packet.Data, len(packet.Data)); err != nil {
return packet, err
}
return packet, nil
}