gstreamer/
promise.rs

1// Take a look at the license at the top of the repository in the LICENSE file.
2
3use std::{
4    ops::Deref,
5    pin::Pin,
6    ptr,
7    task::{Context, Poll},
8};
9
10use glib::translate::*;
11
12use crate::{ffi, PromiseResult, Structure, StructureRef};
13
14glib::wrapper! {
15    #[derive(Debug, PartialEq, Eq, PartialOrd, Ord, Hash)]
16    #[doc(alias = "GstPromise")]
17    pub struct Promise(Shared<ffi::GstPromise>);
18
19    match fn {
20        ref => |ptr| ffi::gst_mini_object_ref(ptr as *mut _),
21        unref => |ptr| ffi::gst_mini_object_unref(ptr as *mut _),
22        type_ => || ffi::gst_promise_get_type(),
23    }
24}
25
26#[derive(Debug, Clone, Copy, PartialEq, Eq, Hash, PartialOrd, Ord)]
27pub enum PromiseError {
28    Interrupted,
29    Expired,
30    Other(PromiseResult),
31}
32
33impl Promise {
34    #[doc(alias = "gst_promise_new")]
35    pub fn new() -> Promise {
36        assert_initialized_main_thread!();
37        unsafe { from_glib_full(ffi::gst_promise_new()) }
38    }
39
40    #[doc(alias = "gst_promise_new_with_change_func")]
41    pub fn with_change_func<F>(func: F) -> Promise
42    where
43        F: FnOnce(Result<Option<&StructureRef>, PromiseError>) + Send + 'static,
44    {
45        assert_initialized_main_thread!();
46        let user_data: Box<Option<F>> = Box::new(Some(func));
47
48        unsafe extern "C" fn trampoline<
49            F: FnOnce(Result<Option<&StructureRef>, PromiseError>) + Send + 'static,
50        >(
51            promise: *mut ffi::GstPromise,
52            user_data: glib::ffi::gpointer,
53        ) {
54            let user_data: &mut Option<F> = &mut *(user_data as *mut _);
55            let callback = user_data.take().unwrap();
56
57            let promise: Borrowed<Promise> = from_glib_borrow(promise);
58
59            let res = match promise.wait() {
60                PromiseResult::Replied => Ok(promise.get_reply()),
61                PromiseResult::Interrupted => Err(PromiseError::Interrupted),
62                PromiseResult::Expired => Err(PromiseError::Expired),
63                PromiseResult::Pending => {
64                    panic!("Promise resolved but returned Pending");
65                }
66                err => Err(PromiseError::Other(err)),
67            };
68
69            callback(res);
70        }
71
72        unsafe extern "C" fn free_user_data<
73            F: FnOnce(Result<Option<&StructureRef>, PromiseError>) + Send + 'static,
74        >(
75            user_data: glib::ffi::gpointer,
76        ) {
77            let _: Box<Option<F>> = Box::from_raw(user_data as *mut _);
78        }
79
80        unsafe {
81            from_glib_full(ffi::gst_promise_new_with_change_func(
82                Some(trampoline::<F>),
83                Box::into_raw(user_data) as *mut _,
84                Some(free_user_data::<F>),
85            ))
86        }
87    }
88
89    pub fn new_future() -> (Self, PromiseFuture) {
90        use futures_channel::oneshot;
91
92        // We only use the channel as a convenient waker
93        let (sender, receiver) = oneshot::channel();
94        let promise = Self::with_change_func(move |_res| {
95            let _ = sender.send(());
96        });
97
98        (promise.clone(), PromiseFuture(promise, receiver))
99    }
100
101    #[doc(alias = "gst_promise_expire")]
102    pub fn expire(&self) {
103        unsafe {
104            ffi::gst_promise_expire(self.to_glib_none().0);
105        }
106    }
107
108    #[doc(alias = "gst_promise_get_reply")]
109    pub fn get_reply(&self) -> Option<&StructureRef> {
110        unsafe {
111            let s = ffi::gst_promise_get_reply(self.to_glib_none().0);
112            if s.is_null() {
113                None
114            } else {
115                Some(StructureRef::from_glib_borrow(s))
116            }
117        }
118    }
119
120    #[doc(alias = "gst_promise_interrupt")]
121    pub fn interrupt(&self) {
122        unsafe {
123            ffi::gst_promise_interrupt(self.to_glib_none().0);
124        }
125    }
126
127    #[doc(alias = "gst_promise_reply")]
128    pub fn reply(&self, s: Option<Structure>) {
129        unsafe {
130            ffi::gst_promise_reply(
131                self.to_glib_none().0,
132                s.map(|s| s.into_glib_ptr()).unwrap_or(ptr::null_mut()),
133            );
134        }
135    }
136
137    #[doc(alias = "gst_promise_wait")]
138    pub fn wait(&self) -> PromiseResult {
139        unsafe { from_glib(ffi::gst_promise_wait(self.to_glib_none().0)) }
140    }
141}
142
143impl Default for Promise {
144    fn default() -> Self {
145        Self::new()
146    }
147}
148
149unsafe impl Send for Promise {}
150unsafe impl Sync for Promise {}
151
152#[derive(Debug)]
153pub struct PromiseFuture(Promise, futures_channel::oneshot::Receiver<()>);
154
155pub struct PromiseReply(Promise);
156
157impl std::future::Future for PromiseFuture {
158    type Output = Result<Option<PromiseReply>, PromiseError>;
159
160    fn poll(mut self: Pin<&mut Self>, context: &mut Context) -> Poll<Self::Output> {
161        match Pin::new(&mut self.1).poll(context) {
162            Poll::Ready(Err(_)) => panic!("Sender dropped before callback was called"),
163            Poll::Ready(Ok(())) => {
164                let res = match self.0.wait() {
165                    PromiseResult::Replied => {
166                        if self.0.get_reply().is_none() {
167                            Ok(None)
168                        } else {
169                            Ok(Some(PromiseReply(self.0.clone())))
170                        }
171                    }
172                    PromiseResult::Interrupted => Err(PromiseError::Interrupted),
173                    PromiseResult::Expired => Err(PromiseError::Expired),
174                    PromiseResult::Pending => {
175                        panic!("Promise resolved but returned Pending");
176                    }
177                    err => Err(PromiseError::Other(err)),
178                };
179                Poll::Ready(res)
180            }
181            Poll::Pending => Poll::Pending,
182        }
183    }
184}
185
186impl futures_core::future::FusedFuture for PromiseFuture {
187    fn is_terminated(&self) -> bool {
188        self.1.is_terminated()
189    }
190}
191
192impl Deref for PromiseReply {
193    type Target = StructureRef;
194
195    #[inline]
196    fn deref(&self) -> &StructureRef {
197        self.0.get_reply().expect("Promise without reply")
198    }
199}
200
201impl std::fmt::Debug for PromiseReply {
202    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
203        let mut debug = f.debug_tuple("PromiseReply");
204
205        match self.0.get_reply() {
206            Some(reply) => debug.field(reply),
207            None => debug.field(&"<no reply>"),
208        }
209        .finish()
210    }
211}
212
213#[cfg(test)]
214mod tests {
215    use std::{sync::mpsc::channel, thread};
216
217    use super::*;
218
219    #[test]
220    fn test_change_func() {
221        crate::init().unwrap();
222
223        let (sender, receiver) = channel();
224        let promise = Promise::with_change_func(move |res| {
225            sender.send(res.map(|s| s.map(ToOwned::to_owned))).unwrap();
226        });
227
228        thread::spawn(move || {
229            promise.reply(Some(crate::Structure::new_empty("foo/bar")));
230        });
231
232        let res = receiver.recv().unwrap();
233        let res = res.expect("promise failed").expect("promise returned None");
234        assert_eq!(res.name(), "foo/bar");
235    }
236}
gstreamer/promise.rs

gstreamer/
promise.rs
