tower/util/boxed/
sync.rs

1use crate::ServiceExt;
2use tower_layer::{layer_fn, LayerFn};
3use tower_service::Service;
4
5use std::fmt;
6use std::{
7    future::Future,
8    pin::Pin,
9    task::{Context, Poll},
10};
11
12/// A boxed `Service + Send` trait object.
13///
14/// [`BoxService`] turns a service into a trait object, allowing the response
15/// future type to be dynamic. This type requires both the service and the
16/// response future to be [`Send`].
17///
18/// If you need a boxed [`Service`] that implements [`Clone`] consider using
19/// [`BoxCloneService`](crate::util::BoxCloneService).
20///
21/// See module level documentation for more details.
22pub struct BoxService<T, U, E> {
23    inner: Box<dyn Service<T, Response = U, Error = E, Future = BoxFuture<U, E>> + Send>,
24}
25
26/// A boxed `Future + Send` trait object.
27///
28/// This type alias represents a boxed future that is [`Send`] and can be moved
29/// across threads.
30type BoxFuture<T, E> = Pin<Box<dyn Future<Output = Result<T, E>> + Send>>;
31
32impl<T, U, E> BoxService<T, U, E> {
33    #[allow(missing_docs)]
34    pub fn new<S>(inner: S) -> Self
35    where
36        S: Service<T, Response = U, Error = E> + Send + 'static,
37        S::Future: Send + 'static,
38    {
39        let inner = Box::new(inner.map_future(|f: S::Future| Box::pin(f) as _));
40        BoxService { inner }
41    }
42
43    /// Returns a [`Layer`] for wrapping a [`Service`] in a [`BoxService`]
44    /// middleware.
45    ///
46    /// [`Layer`]: crate::Layer
47    pub fn layer<S>() -> LayerFn<fn(S) -> Self>
48    where
49        S: Service<T, Response = U, Error = E> + Send + 'static,
50        S::Future: Send + 'static,
51    {
52        layer_fn(Self::new)
53    }
54}
55
56impl<T, U, E> Service<T> for BoxService<T, U, E> {
57    type Response = U;
58    type Error = E;
59    type Future = BoxFuture<U, E>;
60
61    fn poll_ready(&mut self, cx: &mut Context<'_>) -> Poll<Result<(), E>> {
62        self.inner.poll_ready(cx)
63    }
64
65    fn call(&mut self, request: T) -> BoxFuture<U, E> {
66        self.inner.call(request)
67    }
68}
69
70impl<T, U, E> fmt::Debug for BoxService<T, U, E> {
71    fn fmt(&self, fmt: &mut fmt::Formatter) -> fmt::Result {
72        fmt.debug_struct("BoxService").finish()
73    }
74}
tower/util/boxed/sync.rs

tower/util/boxed/
sync.rs
