zbus/message/
mod.rs

1//! D-Bus Message.
2use std::{borrow::Cow, fmt, sync::Arc};
3
4use zbus_names::{ErrorName, InterfaceName, MemberName};
5use zvariant::{serialized, Endian};
6
7use crate::{utils::padding_for_8_bytes, zvariant::ObjectPath, Error, Result};
8
9mod builder;
10pub use builder::Builder;
11
12mod field_code;
13pub(crate) use field_code::FieldCode;
14
15mod fields;
16pub(crate) use fields::Fields;
17use fields::QuickFields;
18
19mod body;
20pub use body::Body;
21
22pub(crate) mod header;
23pub use header::{EndianSig, Flags, Header, PrimaryHeader, Type, NATIVE_ENDIAN_SIG};
24use header::{MIN_MESSAGE_SIZE, PRIMARY_HEADER_SIZE};
25
26/// A position in the stream of [`Message`] objects received by a single [`zbus::Connection`].
27///
28/// Note: the relative ordering of values obtained from distinct [`zbus::Connection`] objects is
29/// not specified; only sequence numbers originating from the same connection should be compared.
30#[derive(Debug, Default, Copy, Clone, Ord, PartialOrd, Eq, PartialEq, Hash)]
31pub struct Sequence {
32    recv_seq: u64,
33}
34
35impl Sequence {
36    /// A sequence number that is higher than any other; used by errors that terminate a stream.
37    pub(crate) const LAST: Self = Self { recv_seq: u64::MAX };
38}
39
40/// A D-Bus Message.
41///
42/// The contents of the message are stored in serialized format. To get the body of the message, use
43/// the [`Message::body`] method, and use [`Body`] methods to deserialize it. You may also access
44/// the header and other details with the various other getters.
45///
46/// Also provided are constructors for messages of different types. These will mainly be useful for
47/// very advanced use cases as typically you will want to create a message for immediate dispatch
48/// and hence use the API provided by [`Connection`], even when using the low-level API.
49///
50/// **Note**: The message owns the received FDs and will close them when dropped. You can
51/// deserialize the body (that you get using [`Message::body`]) to [`zvariant::OwnedFd`] if you want
52/// to keep the FDs around after the containing message is dropped.
53///
54/// [`Connection`]: struct.Connection#method.call_method
55#[derive(Clone)]
56pub struct Message {
57    pub(super) inner: Arc<Inner>,
58}
59
60pub(super) struct Inner {
61    pub(crate) primary_header: PrimaryHeader,
62    pub(crate) quick_fields: std::sync::OnceLock<QuickFields>,
63    pub(crate) bytes: serialized::Data<'static, 'static>,
64    pub(crate) body_offset: usize,
65    pub(crate) recv_seq: Sequence,
66}
67
68impl Message {
69    /// Create a builder for a message of type [`Type::MethodCall`].
70    pub fn method_call<'b, 'p: 'b, 'm: 'b, P, M>(path: P, method_name: M) -> Result<Builder<'b>>
71    where
72        P: TryInto<ObjectPath<'p>>,
73        M: TryInto<MemberName<'m>>,
74        P::Error: Into<Error>,
75        M::Error: Into<Error>,
76    {
77        Builder::new(Type::MethodCall)
78            .path(path)?
79            .member(method_name)
80    }
81
82    /// Create a builder for a message of type [`Type::Signal`].
83    pub fn signal<'b, 'p: 'b, 'i: 'b, 'm: 'b, P, I, M>(
84        path: P,
85        iface: I,
86        signal_name: M,
87    ) -> Result<Builder<'b>>
88    where
89        P: TryInto<ObjectPath<'p>>,
90        I: TryInto<InterfaceName<'i>>,
91        M: TryInto<MemberName<'m>>,
92        P::Error: Into<Error>,
93        I::Error: Into<Error>,
94        M::Error: Into<Error>,
95    {
96        Builder::new(Type::Signal)
97            .path(path)?
98            .interface(iface)?
99            .member(signal_name)
100    }
101
102    /// Create a builder for a message of type [`Type::MethodReturn`].
103    pub fn method_return(reply_to: &Header<'_>) -> Result<Builder<'static>> {
104        Builder::new(Type::MethodReturn).reply_to(reply_to)
105    }
106
107    /// Create a builder for a message of type [`Type::Error`].
108    pub fn error<'b, 'e: 'b, E>(reply_to: &Header<'_>, name: E) -> Result<Builder<'b>>
109    where
110        E: TryInto<ErrorName<'e>>,
111        E::Error: Into<Error>,
112    {
113        Builder::new(Type::Error)
114            .reply_to(reply_to)?
115            .error_name(name)
116    }
117
118    /// Create a message from bytes.
119    ///
120    /// **Note:** Since the message is not constructed by zbus, the receive sequence,
121    /// which can be acquired from [`Message::recv_position`], is not applicable and hence set
122    /// to `0`.
123    ///
124    /// # Safety
125    ///
126    /// This method is unsafe as bytes may have an invalid encoding.
127    pub unsafe fn from_bytes(bytes: serialized::Data<'static, 'static>) -> Result<Self> {
128        Self::from_raw_parts(bytes, 0)
129    }
130
131    /// Create a message from its full contents.
132    pub(crate) fn from_raw_parts(
133        bytes: serialized::Data<'static, 'static>,
134        recv_seq: u64,
135    ) -> Result<Self> {
136        let endian = Endian::from(EndianSig::try_from(bytes[0])?);
137        if endian != bytes.context().endian() {
138            return Err(Error::IncorrectEndian);
139        }
140
141        let (primary_header, fields_len) = PrimaryHeader::read_from_data(&bytes)?;
142        let fields_bytes = bytes.slice(PRIMARY_HEADER_SIZE..);
143        let (fields, _) = fields_bytes.deserialize()?;
144        let header = Header::new(primary_header.clone(), fields);
145
146        let header_len = MIN_MESSAGE_SIZE + fields_len as usize;
147        let body_offset = header_len + padding_for_8_bytes(header_len);
148        let quick_fields = QuickFields::new(&bytes, &header).into();
149
150        Ok(Self {
151            inner: Arc::new(Inner {
152                primary_header,
153                quick_fields,
154                bytes,
155                body_offset,
156                recv_seq: Sequence { recv_seq },
157            }),
158        })
159    }
160
161    pub fn primary_header(&self) -> &PrimaryHeader {
162        &self.inner.primary_header
163    }
164
165    /// The message header.
166    pub fn header(&self) -> Header<'_> {
167        let quick_fields = self.quick_fields();
168        let fields = Fields {
169            path: quick_fields.path(self),
170            interface: quick_fields.interface(self),
171            member: quick_fields.member(self),
172            error_name: quick_fields.error_name(self),
173            reply_serial: quick_fields.reply_serial(),
174            destination: quick_fields.destination(self),
175            sender: quick_fields.sender(self),
176            signature: Cow::Borrowed(quick_fields.signature()),
177            unix_fds: quick_fields.unix_fds(),
178        };
179
180        Header::new(self.inner.primary_header.clone(), fields)
181    }
182
183    /// The message type.
184    pub fn message_type(&self) -> Type {
185        self.inner.primary_header.msg_type()
186    }
187
188    /// The body that you can deserialize using [`Body::deserialize`].
189    ///
190    /// # Example
191    ///
192    /// ```
193    /// # use zbus::message::Message;
194    /// # (|| -> zbus::Result<()> {
195    /// let send_body = (7i32, (2i32, "foo"), vec!["bar"]);
196    /// let message = Message::method_call("/", "ping")?
197    ///     .destination("zbus.test")?
198    ///     .interface("zbus.test")?
199    ///     .build(&send_body)?;
200    /// let header = message.header();
201    /// let body = message.body();
202    /// let body: zbus::zvariant::Structure = body.deserialize()?;
203    /// let fields = body.fields();
204    /// assert!(matches!(fields[0], zvariant::Value::I32(7)));
205    /// assert!(matches!(fields[1], zvariant::Value::Structure(_)));
206    /// assert!(matches!(fields[2], zvariant::Value::Array(_)));
207    ///
208    /// let reply_body = Message::method_return(&header)?.build(&body)?.body();
209    /// let reply_value : (i32, (i32, &str), Vec<String>) = reply_body.deserialize()?;
210    ///
211    /// assert_eq!(reply_value.0, 7);
212    /// assert_eq!(reply_value.2.len(), 1);
213    /// # Ok(()) })().unwrap()
214    /// ```
215    pub fn body(&self) -> Body {
216        Body::new(
217            self.inner.bytes.slice(self.inner.body_offset..),
218            self.clone(),
219        )
220    }
221
222    /// Get a reference to the underlying byte encoding of the message.
223    pub fn data(&self) -> &serialized::Data<'static, 'static> {
224        &self.inner.bytes
225    }
226
227    /// Get the receive ordering of a message.
228    ///
229    /// This may be used to identify how two events were ordered on the bus. It only produces a
230    /// useful ordering for messages that were produced by the same [`zbus::Connection`].
231    ///
232    /// This is completely unrelated to the serial number on the message, which is set by the peer
233    /// and might not be ordered at all.
234    pub fn recv_position(&self) -> Sequence {
235        self.inner.recv_seq
236    }
237
238    fn quick_fields(&self) -> &QuickFields {
239        self.inner.quick_fields.get_or_init(|| {
240            let bytes = &self.inner.bytes;
241            // SAFETY: We ensure that by the time `quick_fields` is called, the header has already
242            // been checked.
243            let (header, _): (Header<'_>, _) = bytes.deserialize().unwrap();
244
245            QuickFields::new(bytes, &header)
246        })
247    }
248}
249
250impl fmt::Debug for Message {
251    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
252        let mut msg = f.debug_struct("Msg");
253        let h = self.header();
254        msg.field("type", &h.message_type());
255        msg.field("serial", &self.primary_header().serial_num());
256        if let Some(sender) = h.sender() {
257            msg.field("sender", &sender);
258        }
259        if let Some(serial) = h.reply_serial() {
260            msg.field("reply-serial", &serial);
261        }
262        if let Some(path) = h.path() {
263            msg.field("path", &path);
264        }
265        if let Some(iface) = h.interface() {
266            msg.field("iface", &iface);
267        }
268        if let Some(member) = h.member() {
269            msg.field("member", &member);
270        }
271        match self.body().signature() {
272            zvariant::Signature::Unit => (),
273            s => {
274                msg.field("body", &s);
275            }
276        }
277        #[cfg(unix)]
278        {
279            msg.field("fds", &self.data().fds());
280        }
281        msg.finish()
282    }
283}
284
285impl fmt::Display for Message {
286    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
287        let header = self.header();
288        let (ty, error_name, sender, member) = (
289            header.message_type(),
290            header.error_name(),
291            header.sender(),
292            header.member(),
293        );
294
295        match ty {
296            Type::MethodCall => {
297                write!(f, "Method call")?;
298                if let Some(m) = member {
299                    write!(f, " {m}")?;
300                }
301            }
302            Type::MethodReturn => {
303                write!(f, "Method return")?;
304            }
305            Type::Error => {
306                write!(f, "Error")?;
307                if let Some(e) = error_name {
308                    write!(f, " {e}")?;
309                }
310
311                let body = self.body();
312                let msg = body.deserialize_unchecked::<&str>();
313                if let Ok(msg) = msg {
314                    write!(f, ": {msg}")?;
315                }
316            }
317            Type::Signal => {
318                write!(f, "Signal")?;
319                if let Some(m) = member {
320                    write!(f, " {m}")?;
321                }
322            }
323        }
324
325        if let Some(s) = sender {
326            write!(f, " from {s}")?;
327        }
328
329        Ok(())
330    }
331}
332
333#[cfg(test)]
334mod tests {
335    #[cfg(unix)]
336    use std::os::fd::{AsFd, AsRawFd};
337    use test_log::test;
338    #[cfg(unix)]
339    use zvariant::Fd;
340    use zvariant::Signature;
341
342    use super::Message;
343    use crate::Error;
344
345    #[test]
346    fn test() {
347        #[cfg(unix)]
348        let stdout = std::io::stdout();
349        let m = Message::method_call("/", "do")
350            .unwrap()
351            .sender(":1.72")
352            .unwrap()
353            .build(&(
354                #[cfg(unix)]
355                Fd::from(&stdout),
356                "foo",
357            ))
358            .unwrap();
359        #[cfg(unix)]
360        assert_eq!(
361            m.body().signature(),
362            &Signature::static_structure(&[&Signature::Fd, &Signature::Str]),
363        );
364        #[cfg(not(unix))]
365        assert_eq!(m.body().signature(), &Signature::Str,);
366        #[cfg(unix)]
367        {
368            let fds = m.data().fds();
369            assert_eq!(fds.len(), 1);
370            // FDs get dup'ed so it has to be a different FD now.
371            assert_ne!(fds[0].as_fd().as_raw_fd(), stdout.as_raw_fd());
372        }
373
374        let body: Result<u32, Error> = m.body().deserialize();
375        assert!(matches!(
376            body.unwrap_err(),
377            Error::Variant(zvariant::Error::SignatureMismatch { .. })
378        ));
379
380        assert_eq!(m.to_string(), "Method call do from :1.72");
381        let r = Message::method_return(&m.header())
382            .unwrap()
383            .build(&("all fine!"))
384            .unwrap();
385        assert_eq!(r.to_string(), "Method return");
386        let e = Message::error(&m.header(), "org.freedesktop.zbus.Error")
387            .unwrap()
388            .build(&("kaboom!", 32))
389            .unwrap();
390        assert_eq!(e.to_string(), "Error org.freedesktop.zbus.Error: kaboom!");
391    }
392}
zbus/message/mod.rs

zbus/message/
mod.rs
