jrouter/atalk/zip/getzonelist.go

129 lines
3.4 KiB
Go

/*
Copyright 2024 Josh Deprez
Licensed under the Apache License, Version 2.0 (the "License");
you may not use this file except in compliance with the License.
You may obtain a copy of the License at
http://www.apache.org/licenses/LICENSE-2.0
Unless required by applicable law or agreed to in writing, software
distributed under the License is distributed on an "AS IS" BASIS,
WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
See the License for the specific language governing permissions and
limitations under the License.
*/
package zip
import (
"bytes"
"encoding/binary"
"fmt"
"drjosh.dev/jrouter/atalk"
"drjosh.dev/jrouter/atalk/atp"
)
type GetZonesPacket struct {
// "These requests always ask for a single response packet."
// TReq = 0b01000000
// Bitmap = 0b00000001
TID uint16
// --- ATP user bytes
Function Function // 7, 8, or 9
// Pad uint8 = 0
StartIndex uint16 // always 0 for
}
func (p *GetZonesPacket) MarshalTReq() (*atp.TReq, error) {
return &atp.TReq{
Bitmap: 0b00000001,
TransactionID: p.TID,
UserBytes: [4]byte{
byte(p.Function), 0, byte(p.StartIndex >> 8), byte(p.StartIndex & 0xFF),
},
}, nil
}
type GetZonesReplyPacket struct {
// TResp = 0b10000000
// Sequence = 0
TID uint16
// --- ATP user bytes
LastFlag bool // not used for GetMyZone
// Pad uint8 = 0
// ZoneCount uint16
// --- ATP data bytes
Zones []string // length-prefixed
}
func (p *GetZonesReplyPacket) MarshalTResp() (*atp.TResp, error) {
r := &atp.TResp{
EndOfMessage: true,
Sequence: 0,
TransactionID: p.TID,
}
if p.LastFlag {
r.UserBytes[0] = 1
}
zc := uint16(len(p.Zones))
r.UserBytes[2] = byte(zc >> 8)
r.UserBytes[3] = byte(zc & 0xFF)
b := bytes.NewBuffer(nil)
for _, z := range p.Zones {
if len(z) > 32 {
return nil, fmt.Errorf("zone name %q too long [%d > 32]", z, len(z))
}
b.WriteByte(byte(len(z)))
b.WriteString(z)
}
r.Data = b.Bytes()
if len(r.Data) > atp.MaxDataSize {
return nil, fmt.Errorf("%w [%d > %d]", atalk.ErrDataTooBig, len(r.Data), atp.MaxDataSize)
}
return r, nil
}
func UnmarshalTReq(treq *atp.TReq) (*GetZonesPacket, error) {
if treq == nil {
return nil, fmt.Errorf("nil *TReq")
}
fn := treq.UserBytes[0]
if fn != FunctionGetZoneList && fn != FunctionGetLocalZones && fn != FunctionGetMyZone {
return nil, fmt.Errorf("invalid ZIP function %d", fn)
}
return &GetZonesPacket{
TID: treq.TransactionID,
Function: Function(treq.UserBytes[0]),
StartIndex: binary.BigEndian.Uint16(treq.UserBytes[2:4]),
}, nil
}
func UnmarshalTResp(tresp *atp.TResp) (*GetZonesReplyPacket, error) {
if tresp == nil {
return nil, fmt.Errorf("nil *TResp")
}
p := &GetZonesReplyPacket{
TID: tresp.TransactionID,
LastFlag: tresp.UserBytes[0] != 0,
}
data := tresp.Data
zc := binary.BigEndian.Uint16(tresp.UserBytes[2:4])
for range zc {
if len(data) < 1 {
return nil, fmt.Errorf("insufficient remaining TResp data length %d for length-prefixed string", len(data))
}
slen := data[0]
data = data[1:]
if len(data) < int(slen) {
return nil, fmt.Errorf("insufficient remaining TResp data length %d for length-%d prefixed string", len(data), slen)
}
p.Zones = append(p.Zones, string(data[:slen]))
data = data[slen:]
}
if len(data) > 0 {
return nil, fmt.Errorf("%d bytes left over at end of packet", len(data))
}
return p, nil
}