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// Package dbus provides a client interface to the D-Bus IPC system.
// It can be used to talk to system services (via the "system bus") or
// services within the user's session (via the "session bus").
package dbus
import (
"errors"
"fmt"
"io"
"log"
"net"
"os"
"strings"
"sync"
"sync/atomic"
)
type StandardBus int
const (
SessionBus StandardBus = iota
SystemBus
)
const (
BUS_DAEMON_NAME = "org.freedesktop.DBus"
BUS_DAEMON_PATH = ObjectPath("/org/freedesktop/DBus")
BUS_DAEMON_IFACE = "org.freedesktop.DBus"
)
type MessageFilter struct {
filter func(*Message) *Message
}
// Connection represents a connection to a message bus.
type Connection struct {
// The unique name of this connection on the message bus.
UniqueName string
conn net.Conn
busProxy BusDaemon
lastSerial uint32
handlerMutex sync.Mutex // covers the next three
messageFilters []*MessageFilter
methodCallReplies map[uint32]chan<- *Message
objectPathHandlers map[ObjectPath]chan<- *Message
signalMatchRules signalWatchSet
nameInfoMutex sync.Mutex
nameInfo map[string]*nameInfo
}
// ObjectProxy represents a remote object on the bus. It can be used
// to simplify constructing method calls, and acts as a basis for
// D-Bus interface client stubs.
type ObjectProxy struct {
bus *Connection
destination string
path ObjectPath
}
func (o *ObjectProxy) ObjectPath() ObjectPath {
return o.path
}
// Call the given method on the remote object.
//
// On success, the reply message will be returned, whose arguments can
// be unpacked with its Args() method.
//
// On failure (both network failures and D-Bus level errors), an error
// will be returned.
func (o *ObjectProxy) Call(iface, method string, args ...interface{}) (*Message, error) {
msg := NewMethodCallMessage(o.destination, o.path, iface, method)
if err := msg.AppendArgs(args...); err != nil {
return nil, err
}
reply, err := o.bus.SendWithReply(msg)
if err != nil {
return nil, err
}
if reply.Type == TypeError {
return nil, reply.AsError()
}
return reply, nil
}
func (o *ObjectProxy) WatchSignal(iface, member string) (*SignalWatch, error) {
return o.bus.WatchSignal(&MatchRule{
Type: TypeSignal,
Sender: o.destination,
Path: o.path,
Interface: iface,
Member: member})
}
// Connect returns a connection to the message bus identified by busType.
func Connect(busType StandardBus) (*Connection, error) {
var address string
switch busType {
case SessionBus:
address = os.Getenv("DBUS_SESSION_BUS_ADDRESS")
case SystemBus:
if address = os.Getenv("DBUS_SYSTEM_BUS_ADDRESS"); len(address) == 0 {
address = "unix:path=/var/run/dbus/system_bus_socket"
}
default:
return nil, errors.New("Unknown bus")
}
trans, err := newTransport(address)
if err != nil {
return nil, err
}
bus := new(Connection)
if bus.conn, err = trans.Dial(); err != nil {
return nil, err
}
if err = authenticate(bus.conn, nil); err != nil {
bus.conn.Close()
return nil, err
}
bus.busProxy = BusDaemon{bus.Object(BUS_DAEMON_NAME, BUS_DAEMON_PATH)}
bus.messageFilters = []*MessageFilter{}
bus.methodCallReplies = make(map[uint32]chan<- *Message)
bus.objectPathHandlers = make(map[ObjectPath]chan<- *Message)
bus.signalMatchRules = make(signalWatchSet)
bus.nameInfo = make(map[string]*nameInfo)
go bus.receiveLoop()
if bus.UniqueName, err = bus.busProxy.Hello(); err != nil {
bus.Close()
return nil, err
}
return bus, nil
}
func (p *Connection) Authenticate() error {
log.Println("dbus.Connection.Authenticate() is deprecated. This call can be removed")
return nil
}
func (p *Connection) receiveLoop() {
for {
msg, err := readMessage(p.conn)
if err != nil {
if err != io.EOF {
log.Println("Failed to read message:", err)
}
break
}
if err = p.dispatchMessage(msg); err != nil {
log.Println("Error dispatching message:", err)
break
}
}
}
func (p *Connection) handlerForPath(objpath ObjectPath) (chan<- *Message, bool) {
p.handlerMutex.Lock()
defer p.handlerMutex.Unlock()
path := string(objpath)
idx := strings.LastIndex(path, "/") + 1
for {
h, ok := p.objectPathHandlers[ObjectPath(path)]
if ok {
return h, true
}
if idx < 1 {
return nil, false
}
idx = strings.LastIndex(path[:idx], "/")
path = path[:idx+1] + "*"
}
}
func (p *Connection) dispatchMessage(msg *Message) error {
// Run the message through the registered filters, stopping
// processing if a filter returns nil.
for _, filter := range p.messageFilters {
msg := filter.filter(msg)
if msg == nil {
return nil
}
}
switch msg.Type {
case TypeMethodCall:
switch {
case msg.Interface == "org.freedesktop.DBus.Peer" && msg.Member == "Ping":
reply := NewMethodReturnMessage(msg)
if err := p.Send(reply); err != nil {
return err
}
case msg.Interface == "org.freedesktop.DBus.Peer" && msg.Member == "GetMachineId":
// Should be returning the UUID found in /var/lib/dbus/machine-id
fmt.Println("XXX: handle GetMachineId")
reply := NewMethodReturnMessage(msg)
if err := reply.AppendArgs("machine-id"); err != nil {
return err
}
if err := p.Send(reply); err != nil {
return err
}
default:
handler, ok := p.handlerForPath(msg.Path)
if ok {
handler <- msg
} else {
reply := NewErrorMessage(msg, "org.freedesktop.DBus.Error.UnknownObject", "Unknown object path "+string(msg.Path))
if err := p.Send(reply); err != nil {
return err
}
}
}
case TypeMethodReturn, TypeError:
p.handlerMutex.Lock()
rs := msg.replySerial
replyChan, ok := p.methodCallReplies[rs]
if ok {
delete(p.methodCallReplies, rs)
}
p.handlerMutex.Unlock()
if ok {
replyChan <- msg
}
case TypeSignal:
p.handlerMutex.Lock()
watches := p.signalMatchRules.FindMatches(msg)
p.handlerMutex.Unlock()
for _, watch := range watches {
watch.C <- msg
}
}
return nil
}
func (p *Connection) Close() error {
return p.conn.Close()
}
func (p *Connection) nextSerial() uint32 {
return atomic.AddUint32(&p.lastSerial, 1)
}
func (p *Connection) Send(msg *Message) error {
msg.setSerial(p.nextSerial())
if _, err := msg.WriteTo(p.conn); err != nil {
return err
}
return nil
}
func (p *Connection) SendWithReply(msg *Message) (*Message, error) {
// XXX: also check for "no reply" flag.
if msg.Type != TypeMethodCall {
panic("Only method calls have replies")
}
serial := p.nextSerial()
msg.setSerial(serial)
replyChan := make(chan *Message, 1)
p.handlerMutex.Lock()
p.methodCallReplies[serial] = replyChan
p.handlerMutex.Unlock()
if _, err := msg.WriteTo(p.conn); err != nil {
p.handlerMutex.Lock()
delete(p.methodCallReplies, serial)
p.handlerMutex.Unlock()
return nil, err
}
reply := <-replyChan
return reply, nil
}
func (p *Connection) RegisterMessageFilter(filter func(*Message) *Message) *MessageFilter {
msgFilter := &MessageFilter{filter}
p.messageFilters = append(p.messageFilters, msgFilter)
return msgFilter
}
func (p *Connection) UnregisterMessageFilter(filter *MessageFilter) {
for i, other := range p.messageFilters {
if other == filter {
p.messageFilters = append(p.messageFilters[:i], p.messageFilters[i+1:]...)
return
}
}
panic("Message filter not registered to this bus")
}
func (p *Connection) RegisterObjectPath(path ObjectPath, handler chan<- *Message) {
p.handlerMutex.Lock()
defer p.handlerMutex.Unlock()
if _, ok := p.objectPathHandlers[path]; ok {
panic("A handler has already been registered for " + string(path))
}
p.objectPathHandlers[path] = handler
}
func (p *Connection) UnregisterObjectPath(path ObjectPath) {
p.handlerMutex.Lock()
defer p.handlerMutex.Unlock()
if _, ok := p.objectPathHandlers[path]; !ok {
panic("No handler registered for " + string(path))
}
delete(p.objectPathHandlers, path)
}
// Object returns a proxy for the object identified by the given
// destination address and path
func (p *Connection) Object(dest string, path ObjectPath) *ObjectProxy {
return &ObjectProxy{p, dest, path}
}
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