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refactor(dbusx): ♻️ clean up code and exports
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@joshuar
joshuar committed May 20, 2024
1 parent 942d089 commit 2af72ae
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Showing 3 changed files with 70 additions and 438 deletions.
12 changes: 6 additions & 6 deletions pkg/linux/dbusx/context.go
View file
Original file line number Diff line number Diff line change
Expand Up @@ -13,16 +13,16 @@ import (
)

type dBusAPI struct {
dbus map[dbusType]*Bus
dbus map[dbusType]*bus
mu sync.Mutex
}

func NewDBusAPI(ctx context.Context) *dBusAPI {
func newDBusAPI(ctx context.Context) *dBusAPI {
a := &dBusAPI{}
a.dbus = make(map[dbusType]*Bus)
a.dbus = make(map[dbusType]*bus)
a.mu.Lock()
for _, b := range []dbusType{SessionBus, SystemBus} {
bus, err := NewBus(ctx, b)
bus, err := newBus(ctx, b)
if err != nil {
log.Warn().Err(err).Msg("Could not connect to D-Bus bus.")
} else {
Expand All @@ -43,11 +43,11 @@ var linuxCtxKey key

// Setup returns a new Context that contains the D-Bus API.
func Setup(ctx context.Context) context.Context {
return context.WithValue(ctx, linuxCtxKey, NewDBusAPI(ctx))
return context.WithValue(ctx, linuxCtxKey, newDBusAPI(ctx))
}

// getBus retrieves the D-Bus API object from the context.
func getBus(ctx context.Context, e dbusType) (*Bus, bool) {
func getBus(ctx context.Context, e dbusType) (*bus, bool) {
b, ok := ctx.Value(linuxCtxKey).(*dBusAPI)
if !ok {
return nil, false
Expand Down
166 changes: 62 additions & 104 deletions pkg/linux/dbusx/dbus.go
View file
Original file line number Diff line number Diff line change
Expand Up @@ -57,6 +57,27 @@ type Watch struct {
Bus dbusType
}

func (w *Watch) Parse() []dbus.MatchOption {
var matchers []dbus.MatchOption
switch {
case w.Path != "":
matchers = append(matchers, dbus.WithMatchObjectPath(dbus.ObjectPath(w.Path)))
case w.PathNamespace != "":
matchers = append(matchers, dbus.WithMatchPathNamespace(dbus.ObjectPath(w.PathNamespace)))
case w.Args != nil:
for arg, value := range w.Args {
matchers = append(matchers, dbus.WithMatchArg(arg, value))
}
case w.Interface != "":
matchers = append(matchers, dbus.WithMatchInterface(w.Interface))
case len(w.Names) != 0:
for _, name := range w.Names {
matchers = append(matchers, dbus.WithMatchMember(name))
}
}
return matchers
}

type Properties struct {
Interface string
Changed map[string]dbus.Variant
Expand All @@ -68,15 +89,15 @@ type Values[T any] struct {
Old T
}

type Bus struct {
type bus struct {
conn *dbus.Conn
busType dbusType
wg sync.WaitGroup
}

// NewBus sets up D-Bus connections and channels for receiving signals. It
// newBus sets up D-Bus connections and channels for receiving signals. It
// creates both a system and session bus connection.
func NewBus(ctx context.Context, t dbusType) (*Bus, error) {
func newBus(ctx context.Context, t dbusType) (*bus, error) {
var conn *dbus.Conn
var err error
dbusCtx, cancelFunc := context.WithCancel(context.Background())
Expand All @@ -90,7 +111,7 @@ func NewBus(ctx context.Context, t dbusType) (*Bus, error) {
cancelFunc()
return nil, err
}
b := &Bus{
b := &bus{
conn: conn,
busType: t,
}
Expand All @@ -103,9 +124,9 @@ func NewBus(ctx context.Context, t dbusType) (*Bus, error) {
return b, nil
}

// busRequest contains properties for building different types of D-Bus requests.
type busRequest struct {
bus *Bus
// BusRequest contains properties for building different types of D-Bus requests.
type BusRequest struct {
bus *bus
eventHandler func(*dbus.Signal)
path dbus.ObjectPath
event string
Expand All @@ -117,56 +138,69 @@ type busRequest struct {
// (either a system or session bus). If it cannot connect to the specified bus,
// it will still return a busRequest object. Further builder functions should
// check whether there is a valid bus if appropriate.
func NewBusRequest(ctx context.Context, busType dbusType) *busRequest {
func NewBusRequest(ctx context.Context, busType dbusType) *BusRequest {
if bus, ok := getBus(ctx, busType); !ok {
log.Debug().Msg("No D-Bus connection present in context.")
return &busRequest{}
return &BusRequest{}
} else {
return &busRequest{
return &BusRequest{
bus: bus,
}
}
}

// Path defines the D-Bus path on which a request will operate.
func (r *busRequest) Path(p dbus.ObjectPath) *busRequest {
func (r *BusRequest) Path(p dbus.ObjectPath) *BusRequest {
r.path = p
return r
}

// Match defines D-Bus routing match rules on which a request will operate.
func (r *busRequest) Match(m []dbus.MatchOption) *busRequest {
func (r *BusRequest) Match(m []dbus.MatchOption) *BusRequest {
r.match = m
return r
}

// Event defines an event on which a D-Bus request should match.
func (r *busRequest) Event(e string) *busRequest {
func (r *BusRequest) Event(e string) *BusRequest {
r.event = e
return r
}

// Handler defines a function that will handle a matched D-Bus signal.
func (r *busRequest) Handler(h func(*dbus.Signal)) *busRequest {
func (r *BusRequest) Handler(h func(*dbus.Signal)) *BusRequest {
r.eventHandler = h
return r
}

// Destination defines the location/interface on a given D-Bus path for a request
// to operate.
func (r *busRequest) Destination(d string) *busRequest {
func (r *BusRequest) Destination(d string) *BusRequest {
r.dest = d
return r
}

// Call executes the given method in the builder and returns the error state.
func (r *BusRequest) Call(method string, args ...any) error {
if r.bus == nil {
return ErrNoBus
}
obj := r.bus.conn.Object(r.dest, r.path)
if args != nil {
return fmt.Errorf("%s: call could not retrieve object (%w)", r.bus.busType.String(), obj.Call(method, 0, args...).Err)
}
return obj.Call(method, 0).Err
}

// GetProp uses the given request builder to fetch the specified property from
// D-Bus as the given type. If the property cannot be retrieved, a non-nil error
// is returned.
func GetProp[P any](req *busRequest, prop string) (P, error) {
func GetProp[P any](req *BusRequest, prop string) (P, error) {
var value P
if req == nil || req.bus == nil {
return value, ErrNoBus
}
log.Trace().Str("path", string(req.path)).Str("dest", req.dest).Str("property", prop).Msgf("Requesting property (as %T).", value)
obj := req.bus.conn.Object(req.dest, req.path)
res, err := obj.GetProperty(prop)
if err != nil {
Expand All @@ -176,7 +210,7 @@ func GetProp[P any](req *busRequest, prop string) (P, error) {
}

// SetProp sets the specific property to the specified value.
func SetProp[P any](req *busRequest, prop string, value P) error {
func SetProp[P any](req *BusRequest, prop string, value P) error {
if req == nil || req.bus == nil {
return ErrNoBus
}
Expand All @@ -188,7 +222,7 @@ func SetProp[P any](req *busRequest, prop string, value P) error {
// GetData uses the given request builder to fetch D-Bus data from the given
// method, as the provided type. If there is an error or the result cannot be
// stored in the given type, it will return an non-nil error.
func GetData[D any](req *busRequest, method string, args ...any) (D, error) {
func GetData[D any](req *BusRequest, method string, args ...any) (D, error) {
var data D
if req == nil || req.bus == nil {
return data, ErrNoBus
Expand All @@ -203,18 +237,6 @@ func GetData[D any](req *busRequest, method string, args ...any) (D, error) {
return data, err
}

// Call executes the given method in the builder and returns the error state.
func (r *busRequest) Call(method string, args ...any) error {
if r.bus == nil {
return ErrNoBus
}
obj := r.bus.conn.Object(r.dest, r.path)
if args != nil {
return r.busRequestError("call could not retrieve object", obj.Call(method, 0, args...).Err)
}
return obj.Call(method, 0).Err
}

// WatchBus will set up a channel on which D-Bus messages matching the given
// rules can be monitored. Typically, this is used to react when a certain
// property or signal with a given path and on a given interface, changes. The
Expand All @@ -226,26 +248,12 @@ func WatchBus(ctx context.Context, conditions *Watch) (chan Trigger, error) {
if !ok {
return nil, ErrNoBusCtx
}
var matchers []dbus.MatchOption
switch {
case conditions.Path != "":
matchers = append(matchers, dbus.WithMatchObjectPath(dbus.ObjectPath(conditions.Path)))
case conditions.PathNamespace != "":
matchers = append(matchers, dbus.WithMatchPathNamespace(dbus.ObjectPath(conditions.PathNamespace)))
case conditions.Args != nil:
for arg, value := range conditions.Args {
matchers = append(matchers, dbus.WithMatchArg(arg, value))
}
case conditions.Interface != "":
matchers = append(matchers, dbus.WithMatchInterface(conditions.Interface))
case len(conditions.Names) != 0:
for _, name := range conditions.Names {
matchers = append(matchers, dbus.WithMatchMember(name))
}
}

matchers := conditions.Parse()
if err := bus.conn.AddMatchSignalContext(ctx, matchers...); err != nil {
return nil, fmt.Errorf("unable to add watch conditions (%w)", err)
}

signalCh := make(chan *dbus.Signal)
outCh := make(chan Trigger)
bus.conn.Signal(signalCh)
Expand Down Expand Up @@ -299,59 +307,6 @@ func WatchBus(ctx context.Context, conditions *Watch) (chan Trigger, error) {
return outCh, nil
}

func (r *busRequest) AddWatch(ctx context.Context) error {
if r.bus == nil {
return ErrNoBus
}
if err := r.bus.conn.AddMatchSignalContext(ctx, r.match...); err != nil {
return err
}
signalCh := make(chan *dbus.Signal)
r.bus.conn.Signal(signalCh)
r.bus.wg.Add(1)
var wg sync.WaitGroup
wg.Add(1)
go func() {
defer wg.Done()
for {
select {
case <-ctx.Done():
r.bus.conn.RemoveSignal(signalCh)
close(signalCh)
return
case signal := <-signalCh:
r.eventHandler(signal)
}
}
}()
go func() {
wg.Wait()
r.bus.wg.Done()
}()
return nil
}

func (r *busRequest) RemoveWatch(ctx context.Context) error {
if r.bus == nil {
return ErrNoBus
}
if err := r.bus.conn.RemoveMatchSignalContext(ctx, r.match...); err != nil {
return r.busRequestError("unable to remove watch", err)
}
log.Trace().
Str("path", string(r.path)).
Str("dest", r.dest).
Str("event", r.event).
Msgf("Removed D-Bus signal.")
return nil
}

// busRequestError wraps a lower level error while creating a busRequest into
// something more understandable.
func (r *busRequest) busRequestError(msg string, err error) error {
return fmt.Errorf("%s: %s (%w)", r.bus.busType.String(), msg, err)
}

func GetSessionPath(ctx context.Context) dbus.ObjectPath {
u, err := user.Current()
if err != nil {
Expand All @@ -377,7 +332,8 @@ func GetSessionPath(ctx context.Context) dbus.ObjectPath {

// ParsePropertiesChanged treats the given signal body as matching the canonical
// org.freedesktop.DBus.PropertiesChanged signature and will parse it into a
// Properties structure that is easier to use. Adapted from
// Properties structure that is easier to use. If the signal body cannot be
// parsed an error will be returned with details of the problem. Adapted from
// https://github.com/godbus/dbus/issues/201
func ParsePropertiesChanged(v []any) (*Properties, error) {
props := &Properties{}
Expand All @@ -402,7 +358,9 @@ func ParsePropertiesChanged(v []any) (*Properties, error) {

// ParseValueChange treats the given signal body as matching a value change of a
// property from an old value to a new value. It will parse the signal body into
// a Value object with old/new values of the given type.
// a Value object with old/new values of the given type. If there was a problem
// parsing the signal body, an error will be returned with details of the
// problem.
func ParseValueChange[T any](v []any) (*Values[T], error) {
values := &Values[T]{}
var ok bool
Expand All @@ -420,8 +378,8 @@ func ParseValueChange[T any](v []any) (*Values[T], error) {
return values, nil
}

// VariantToValue converts a dbus.Variant interface{} value into the specified
// Go native type. If the value is nil, then the return value will be the
// VariantToValue converts a dbus.Variant value into the specified Go type. If
// the value is nil or it cannot be converted, then the return value will be the
// default value of the specified type.
func VariantToValue[S any](variant dbus.Variant) S {
var value S
Expand Down
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