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This commit is contained in:
Jakob Borg
2013-12-22 21:35:05 -05:00
parent 31ea72dbb3
commit f2d8b68278
5 changed files with 162 additions and 99 deletions
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52
discover/encoding.go
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@@ -6,11 +6,11 @@ import (
"fmt"
)
type packet struct {
magic uint32 // AnnouncementMagic or QueryMagic
port uint16 // unset if magic == QueryMagic
id string
ip []byte // zero length in local announcements
type Packet struct {
Magic uint32 // AnnouncementMagic or QueryMagic
Port uint16 // unset if magic == QueryMagic
ID string
IP []byte // zero length in local announcements
}
var (
@@ -18,26 +18,26 @@ var (
errFormat = errors.New("incorrect packet format")
)
func encodePacket(pkt packet) []byte {
if l := len(pkt.ip); l != 0 && l != 4 && l != 16 {
func EncodePacket(pkt Packet) []byte {
if l := len(pkt.IP); l != 0 && l != 4 && l != 16 {
// bad ip format
return nil
}
var idbs = []byte(pkt.id)
var idbs = []byte(pkt.ID)
var l = 4 + 4 + len(idbs) + pad(len(idbs))
if pkt.magic == AnnouncementMagic {
l += 4 + 4 + len(pkt.ip)
if pkt.Magic == AnnouncementMagic {
l += 4 + 4 + len(pkt.IP)
}
var buf = make([]byte, l)
var offset = 0
binary.BigEndian.PutUint32(buf[offset:], pkt.magic)
binary.BigEndian.PutUint32(buf[offset:], pkt.Magic)
offset += 4
if pkt.magic == AnnouncementMagic {
binary.BigEndian.PutUint16(buf[offset:], uint16(pkt.port))
if pkt.Magic == AnnouncementMagic {
binary.BigEndian.PutUint16(buf[offset:], uint16(pkt.Port))
offset += 4
}
@@ -46,39 +46,39 @@ func encodePacket(pkt packet) []byte {
copy(buf[offset:], idbs)
offset += len(idbs) + pad(len(idbs))
if pkt.magic == AnnouncementMagic {
binary.BigEndian.PutUint32(buf[offset:], uint32(len(pkt.ip)))
if pkt.Magic == AnnouncementMagic {
binary.BigEndian.PutUint32(buf[offset:], uint32(len(pkt.IP)))
offset += 4
copy(buf[offset:], pkt.ip)
offset += len(pkt.ip)
copy(buf[offset:], pkt.IP)
offset += len(pkt.IP)
}
return buf
}
func decodePacket(buf []byte) (*packet, error) {
var p packet
func DecodePacket(buf []byte) (*Packet, error) {
var p Packet
var offset int
if len(buf) < 4 {
// short packet
return nil, errFormat
}
p.magic = binary.BigEndian.Uint32(buf[offset:])
p.Magic = binary.BigEndian.Uint32(buf[offset:])
offset += 4
if p.magic != AnnouncementMagic && p.magic != QueryMagic {
if p.Magic != AnnouncementMagic && p.Magic != QueryMagic {
return nil, errBadMagic
}
if p.magic == AnnouncementMagic {
if p.Magic == AnnouncementMagic {
// Port Number
if len(buf) < offset+4 {
// short packet
return nil, errFormat
}
p.port = binary.BigEndian.Uint16(buf[offset:])
p.Port = binary.BigEndian.Uint16(buf[offset:])
offset += 2
reserved := binary.BigEndian.Uint16(buf[offset:])
if reserved != 0 {
@@ -101,10 +101,10 @@ func decodePacket(buf []byte) (*packet, error) {
return nil, errFormat
}
idbs := buf[offset : offset+int(l)]
p.id = string(idbs)
p.ID = string(idbs)
offset += int(l) + pad(int(l))
if p.magic == AnnouncementMagic {
if p.Magic == AnnouncementMagic {
// IP
if len(buf) < offset+4 {
@@ -123,7 +123,7 @@ func decodePacket(buf []byte) (*packet, error) {
return nil, errFormat
}
if l > 0 {
p.ip = buf[offset : offset+int(l)]
p.IP = buf[offset : offset+int(l)]
offset += int(l)
}
}