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package dbus
import (
"bytes"
"encoding/binary"
"errors"
"io"
"reflect"
"strconv"
)
const protoVersion byte = 1
// Flags represents the possible flags of a D-Bus message.
type Flags byte
const (
// FlagNoReplyExpected signals that the message is not expected to generate
// a reply. If this flag is set on outgoing messages, any possible reply
// will be discarded.
FlagNoReplyExpected Flags = 1 << iota
// FlagNoAutoStart signals that the message bus should not automatically
// start an application when handling this message.
FlagNoAutoStart
// FlagAllowInteractiveAuthorization may be set on a method call
// message to inform the receiving side that the caller is prepared
// to wait for interactive authorization, which might take a
// considerable time to complete. For instance, if this flag is set,
// it would be appropriate to query the user for passwords or
// confirmation via Polkit or a similar framework.
FlagAllowInteractiveAuthorization
)
// Type represents the possible types of a D-Bus message.
type Type byte
const (
TypeMethodCall Type = 1 + iota
TypeMethodReply
TypeError
TypeSignal
typeMax
)
func (t Type) String() string {
switch t {
case TypeMethodCall:
return "method call"
case TypeMethodReply:
return "reply"
case TypeError:
return "error"
case TypeSignal:
return "signal"
}
return "invalid"
}
// HeaderField represents the possible byte codes for the headers
// of a D-Bus message.
type HeaderField byte
const (
FieldPath HeaderField = 1 + iota
FieldInterface
FieldMember
FieldErrorName
FieldReplySerial
FieldDestination
FieldSender
FieldSignature
FieldUnixFDs
fieldMax
)
// An InvalidMessageError describes the reason why a D-Bus message is regarded as
// invalid.
type InvalidMessageError string
func (e InvalidMessageError) Error() string {
return "dbus: invalid message: " + string(e)
}
// fieldType are the types of the various header fields.
var fieldTypes = [fieldMax]reflect.Type{
FieldPath: objectPathType,
FieldInterface: stringType,
FieldMember: stringType,
FieldErrorName: stringType,
FieldReplySerial: uint32Type,
FieldDestination: stringType,
FieldSender: stringType,
FieldSignature: signatureType,
FieldUnixFDs: uint32Type,
}
// requiredFields lists the header fields that are required by the different
// message types.
var requiredFields = [typeMax][]HeaderField{
TypeMethodCall: {FieldPath, FieldMember},
TypeMethodReply: {FieldReplySerial},
TypeError: {FieldErrorName, FieldReplySerial},
TypeSignal: {FieldPath, FieldInterface, FieldMember},
}
// Message represents a single D-Bus message.
type Message struct {
Type
Flags
Headers map[HeaderField]Variant
Body []interface{}
serial uint32
}
type header struct {
Field byte
Variant
}
// DecodeMessage tries to decode a single message in the D-Bus wire format
// from the given reader. The byte order is figured out from the first byte.
// The possibly returned error can be an error of the underlying reader, an
// InvalidMessageError or a FormatError.
func DecodeMessage(rd io.Reader) (msg *Message, err error) {
var order binary.ByteOrder
var hlength, length uint32
var typ, flags, proto byte
var headers []header
b := make([]byte, 1)
_, err = rd.Read(b)
if err != nil {
return
}
switch b[0] {
case 'l':
order = binary.LittleEndian
case 'B':
order = binary.BigEndian
default:
return nil, InvalidMessageError("invalid byte order")
}
dec := newDecoder(rd, order)
dec.pos = 1
msg = new(Message)
vs, err := dec.Decode(Signature{"yyyuu"})
if err != nil {
return nil, err
}
if err = Store(vs, &typ, &flags, &proto, &length, &msg.serial); err != nil {
return nil, err
}
msg.Type = Type(typ)
msg.Flags = Flags(flags)
// get the header length separately because we need it later
b = make([]byte, 4)
_, err = io.ReadFull(rd, b)
if err != nil {
return nil, err
}
binary.Read(bytes.NewBuffer(b), order, &hlength)
if hlength+length+16 > 1<<27 {
return nil, InvalidMessageError("message is too long")
}
dec = newDecoder(io.MultiReader(bytes.NewBuffer(b), rd), order)
dec.pos = 12
vs, err = dec.Decode(Signature{"a(yv)"})
if err != nil {
return nil, err
}
if err = Store(vs, &headers); err != nil {
return nil, err
}
msg.Headers = make(map[HeaderField]Variant)
for _, v := range headers {
msg.Headers[HeaderField(v.Field)] = v.Variant
}
dec.align(8)
body := make([]byte, int(length))
if length != 0 {
_, err := io.ReadFull(rd, body)
if err != nil {
return nil, err
}
}
if err = msg.IsValid(); err != nil {
return nil, err
}
sig, _ := msg.Headers[FieldSignature].value.(Signature)
if sig.str != "" {
buf := bytes.NewBuffer(body)
dec = newDecoder(buf, order)
vs, err := dec.Decode(sig)
if err != nil {
return nil, err
}
msg.Body = vs
}
return
}
// EncodeTo encodes and sends a message to the given writer. The byte order must
// be either binary.LittleEndian or binary.BigEndian. If the message is not
// valid or an error occurs when writing, an error is returned.
func (msg *Message) EncodeTo(out io.Writer, order binary.ByteOrder) error {
if err := msg.IsValid(); err != nil {
return err
}
var vs [7]interface{}
switch order {
case binary.LittleEndian:
vs[0] = byte('l')
case binary.BigEndian:
vs[0] = byte('B')
default:
return errors.New("dbus: invalid byte order")
}
body := new(bytes.Buffer)
enc := newEncoder(body, order)
if len(msg.Body) != 0 {
enc.Encode(msg.Body...)
}
vs[1] = msg.Type
vs[2] = msg.Flags
vs[3] = protoVersion
vs[4] = uint32(len(body.Bytes()))
vs[5] = msg.serial
headers := make([]header, 0, len(msg.Headers))
for k, v := range msg.Headers {
headers = append(headers, header{byte(k), v})
}
vs[6] = headers
var buf bytes.Buffer
enc = newEncoder(&buf, order)
enc.Encode(vs[:]...)
enc.align(8)
body.WriteTo(&buf)
if buf.Len() > 1<<27 {
return InvalidMessageError("message is too long")
}
if _, err := buf.WriteTo(out); err != nil {
return err
}
return nil
}
// IsValid checks whether msg is a valid message and returns an
// InvalidMessageError if it is not.
func (msg *Message) IsValid() error {
if msg.Flags & ^(FlagNoAutoStart|FlagNoReplyExpected|FlagAllowInteractiveAuthorization) != 0 {
return InvalidMessageError("invalid flags")
}
if msg.Type == 0 || msg.Type >= typeMax {
return InvalidMessageError("invalid message type")
}
for k, v := range msg.Headers {
if k == 0 || k >= fieldMax {
return InvalidMessageError("invalid header")
}
if reflect.TypeOf(v.value) != fieldTypes[k] {
return InvalidMessageError("invalid type of header field")
}
}
for _, v := range requiredFields[msg.Type] {
if _, ok := msg.Headers[v]; !ok {
return InvalidMessageError("missing required header")
}
}
if path, ok := msg.Headers[FieldPath]; ok {
if !path.value.(ObjectPath).IsValid() {
return InvalidMessageError("invalid path name")
}
}
if iface, ok := msg.Headers[FieldInterface]; ok {
if !isValidInterface(iface.value.(string)) {
return InvalidMessageError("invalid interface name")
}
}
if member, ok := msg.Headers[FieldMember]; ok {
if !isValidMember(member.value.(string)) {
return InvalidMessageError("invalid member name")
}
}
if errname, ok := msg.Headers[FieldErrorName]; ok {
if !isValidInterface(errname.value.(string)) {
return InvalidMessageError("invalid error name")
}
}
if len(msg.Body) != 0 {
if _, ok := msg.Headers[FieldSignature]; !ok {
return InvalidMessageError("missing signature")
}
}
return nil
}
// Serial returns the message's serial number. The returned value is only valid
// for messages received by eavesdropping.
func (msg *Message) Serial() uint32 {
return msg.serial
}
// String returns a string representation of a message similar to the format of
// dbus-monitor.
func (msg *Message) String() string {
if err := msg.IsValid(); err != nil {
return "<invalid>"
}
s := msg.Type.String()
if v, ok := msg.Headers[FieldSender]; ok {
s += " from " + v.value.(string)
}
if v, ok := msg.Headers[FieldDestination]; ok {
s += " to " + v.value.(string)
}
s += " serial " + strconv.FormatUint(uint64(msg.serial), 10)
if v, ok := msg.Headers[FieldReplySerial]; ok {
s += " reply_serial " + strconv.FormatUint(uint64(v.value.(uint32)), 10)
}
if v, ok := msg.Headers[FieldUnixFDs]; ok {
s += " unixfds " + strconv.FormatUint(uint64(v.value.(uint32)), 10)
}
if v, ok := msg.Headers[FieldPath]; ok {
s += " path " + string(v.value.(ObjectPath))
}
if v, ok := msg.Headers[FieldInterface]; ok {
s += " interface " + v.value.(string)
}
if v, ok := msg.Headers[FieldErrorName]; ok {
s += " error " + v.value.(string)
}
if v, ok := msg.Headers[FieldMember]; ok {
s += " member " + v.value.(string)
}
if len(msg.Body) != 0 {
s += "\n"
}
for i, v := range msg.Body {
s += " " + MakeVariant(v).String()
if i != len(msg.Body)-1 {
s += "\n"
}
}
return s
}
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