1 | use crate::{FutureObj, LocalFutureObj}; |
2 | use core::fmt; |
3 | |
4 | /// The `Spawn` trait allows for pushing futures onto an executor that will |
5 | /// run them to completion. |
6 | pub trait Spawn { |
7 | /// Spawns a future that will be run to completion. |
8 | /// |
9 | /// # Errors |
10 | /// |
11 | /// The executor may be unable to spawn tasks. Spawn errors should |
12 | /// represent relatively rare scenarios, such as the executor |
13 | /// having been shut down so that it is no longer able to accept |
14 | /// tasks. |
15 | fn spawn_obj(&self, future: FutureObj<'static, ()>) -> Result<(), SpawnError>; |
16 | |
17 | /// Determines whether the executor is able to spawn new tasks. |
18 | /// |
19 | /// This method will return `Ok` when the executor is *likely* |
20 | /// (but not guaranteed) to accept a subsequent spawn attempt. |
21 | /// Likewise, an `Err` return means that `spawn` is likely, but |
22 | /// not guaranteed, to yield an error. |
23 | #[inline ] |
24 | fn status(&self) -> Result<(), SpawnError> { |
25 | Ok(()) |
26 | } |
27 | } |
28 | |
29 | /// The `LocalSpawn` is similar to [`Spawn`], but allows spawning futures |
30 | /// that don't implement `Send`. |
31 | pub trait LocalSpawn { |
32 | /// Spawns a future that will be run to completion. |
33 | /// |
34 | /// # Errors |
35 | /// |
36 | /// The executor may be unable to spawn tasks. Spawn errors should |
37 | /// represent relatively rare scenarios, such as the executor |
38 | /// having been shut down so that it is no longer able to accept |
39 | /// tasks. |
40 | fn spawn_local_obj(&self, future: LocalFutureObj<'static, ()>) -> Result<(), SpawnError>; |
41 | |
42 | /// Determines whether the executor is able to spawn new tasks. |
43 | /// |
44 | /// This method will return `Ok` when the executor is *likely* |
45 | /// (but not guaranteed) to accept a subsequent spawn attempt. |
46 | /// Likewise, an `Err` return means that `spawn` is likely, but |
47 | /// not guaranteed, to yield an error. |
48 | #[inline ] |
49 | fn status_local(&self) -> Result<(), SpawnError> { |
50 | Ok(()) |
51 | } |
52 | } |
53 | |
54 | /// An error that occurred during spawning. |
55 | pub struct SpawnError { |
56 | _priv: (), |
57 | } |
58 | |
59 | impl fmt::Debug for SpawnError { |
60 | fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result { |
61 | f.debug_tuple(name:"SpawnError" ).field(&"shutdown" ).finish() |
62 | } |
63 | } |
64 | |
65 | impl fmt::Display for SpawnError { |
66 | fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result { |
67 | write!(f, "Executor is shutdown" ) |
68 | } |
69 | } |
70 | |
71 | #[cfg (feature = "std" )] |
72 | impl std::error::Error for SpawnError {} |
73 | |
74 | impl SpawnError { |
75 | /// Spawning failed because the executor has been shut down. |
76 | pub fn shutdown() -> Self { |
77 | Self { _priv: () } |
78 | } |
79 | |
80 | /// Check whether spawning failed to the executor being shut down. |
81 | pub fn is_shutdown(&self) -> bool { |
82 | true |
83 | } |
84 | } |
85 | |
86 | impl<Sp: ?Sized + Spawn> Spawn for &Sp { |
87 | fn spawn_obj(&self, future: FutureObj<'static, ()>) -> Result<(), SpawnError> { |
88 | Sp::spawn_obj(self, future) |
89 | } |
90 | |
91 | fn status(&self) -> Result<(), SpawnError> { |
92 | Sp::status(self) |
93 | } |
94 | } |
95 | |
96 | impl<Sp: ?Sized + Spawn> Spawn for &mut Sp { |
97 | fn spawn_obj(&self, future: FutureObj<'static, ()>) -> Result<(), SpawnError> { |
98 | Sp::spawn_obj(self, future) |
99 | } |
100 | |
101 | fn status(&self) -> Result<(), SpawnError> { |
102 | Sp::status(self) |
103 | } |
104 | } |
105 | |
106 | impl<Sp: ?Sized + LocalSpawn> LocalSpawn for &Sp { |
107 | fn spawn_local_obj(&self, future: LocalFutureObj<'static, ()>) -> Result<(), SpawnError> { |
108 | Sp::spawn_local_obj(self, future) |
109 | } |
110 | |
111 | fn status_local(&self) -> Result<(), SpawnError> { |
112 | Sp::status_local(self) |
113 | } |
114 | } |
115 | |
116 | impl<Sp: ?Sized + LocalSpawn> LocalSpawn for &mut Sp { |
117 | fn spawn_local_obj(&self, future: LocalFutureObj<'static, ()>) -> Result<(), SpawnError> { |
118 | Sp::spawn_local_obj(self, future) |
119 | } |
120 | |
121 | fn status_local(&self) -> Result<(), SpawnError> { |
122 | Sp::status_local(self) |
123 | } |
124 | } |
125 | |
126 | #[cfg (feature = "alloc" )] |
127 | mod if_alloc { |
128 | use super::*; |
129 | use alloc::{boxed::Box, rc::Rc}; |
130 | |
131 | impl<Sp: ?Sized + Spawn> Spawn for Box<Sp> { |
132 | fn spawn_obj(&self, future: FutureObj<'static, ()>) -> Result<(), SpawnError> { |
133 | (**self).spawn_obj(future) |
134 | } |
135 | |
136 | fn status(&self) -> Result<(), SpawnError> { |
137 | (**self).status() |
138 | } |
139 | } |
140 | |
141 | impl<Sp: ?Sized + LocalSpawn> LocalSpawn for Box<Sp> { |
142 | fn spawn_local_obj(&self, future: LocalFutureObj<'static, ()>) -> Result<(), SpawnError> { |
143 | (**self).spawn_local_obj(future) |
144 | } |
145 | |
146 | fn status_local(&self) -> Result<(), SpawnError> { |
147 | (**self).status_local() |
148 | } |
149 | } |
150 | |
151 | impl<Sp: ?Sized + Spawn> Spawn for Rc<Sp> { |
152 | fn spawn_obj(&self, future: FutureObj<'static, ()>) -> Result<(), SpawnError> { |
153 | (**self).spawn_obj(future) |
154 | } |
155 | |
156 | fn status(&self) -> Result<(), SpawnError> { |
157 | (**self).status() |
158 | } |
159 | } |
160 | |
161 | impl<Sp: ?Sized + LocalSpawn> LocalSpawn for Rc<Sp> { |
162 | fn spawn_local_obj(&self, future: LocalFutureObj<'static, ()>) -> Result<(), SpawnError> { |
163 | (**self).spawn_local_obj(future) |
164 | } |
165 | |
166 | fn status_local(&self) -> Result<(), SpawnError> { |
167 | (**self).status_local() |
168 | } |
169 | } |
170 | |
171 | #[cfg (not(futures_no_atomic_cas))] |
172 | impl<Sp: ?Sized + Spawn> Spawn for alloc::sync::Arc<Sp> { |
173 | fn spawn_obj(&self, future: FutureObj<'static, ()>) -> Result<(), SpawnError> { |
174 | (**self).spawn_obj(future) |
175 | } |
176 | |
177 | fn status(&self) -> Result<(), SpawnError> { |
178 | (**self).status() |
179 | } |
180 | } |
181 | |
182 | #[cfg (not(futures_no_atomic_cas))] |
183 | impl<Sp: ?Sized + LocalSpawn> LocalSpawn for alloc::sync::Arc<Sp> { |
184 | fn spawn_local_obj(&self, future: LocalFutureObj<'static, ()>) -> Result<(), SpawnError> { |
185 | (**self).spawn_local_obj(future) |
186 | } |
187 | |
188 | fn status_local(&self) -> Result<(), SpawnError> { |
189 | (**self).status_local() |
190 | } |
191 | } |
192 | } |
193 | |