package dht import ( "encoding/binary" "errors" "net" "github.com/anacrolix/missinggo" ) // The size in bytes of a NodeInfo in its compact binary representation. const CompactIPv4NodeInfoLen = 26 type NodeInfo struct { ID [20]byte Addr Addr } // Writes the node info to its compact binary representation in b. See // CompactNodeInfoLen. func (ni *NodeInfo) PutCompact(b []byte) error { if n := copy(b[:], ni.ID[:]); n != 20 { panic(n) } ip := ni.Addr.UDPAddr().IP.To4() if len(ip) != 4 { return errors.New("expected ipv4 address") } if n := copy(b[20:], ip); n != 4 { panic(n) } binary.BigEndian.PutUint16(b[24:], uint16(ni.Addr.UDPAddr().Port)) return nil } func (cni *NodeInfo) UnmarshalCompactIPv4(b []byte) error { if len(b) != CompactIPv4NodeInfoLen { return errors.New("expected 26 bytes") } missinggo.CopyExact(cni.ID[:], b[:20]) cni.Addr = NewAddr(&net.UDPAddr{ IP: append(make([]byte, 0, 4), b[20:24]...), Port: int(binary.BigEndian.Uint16(b[24:26])), }) return nil }