Jason Macnak | ea22e81 | 2020-03-18 01:29:19 +0000 | [diff] [blame] | 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("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_target_has_atomic! { |
| 172 | use alloc::{ sync::Arc }; |
| 173 | |
| 174 | impl<Sp: ?Sized + Spawn> Spawn for Arc<Sp> { |
| 175 | fn spawn_obj(&self, future: FutureObj<'static, ()>) -> Result<(), SpawnError> { |
| 176 | (**self).spawn_obj(future) |
| 177 | } |
| 178 | |
| 179 | fn status(&self) -> Result<(), SpawnError> { |
| 180 | (**self).status() |
| 181 | } |
| 182 | } |
| 183 | |
| 184 | impl<Sp: ?Sized + LocalSpawn> LocalSpawn for Arc<Sp> { |
| 185 | fn spawn_local_obj(&self, future: LocalFutureObj<'static, ()>) -> Result<(), SpawnError> { |
| 186 | (**self).spawn_local_obj(future) |
| 187 | } |
| 188 | |
| 189 | fn status_local(&self) -> Result<(), SpawnError> { |
| 190 | (**self).status_local() |
| 191 | } |
| 192 | } |
| 193 | } |
| 194 | } |