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