Add polling for target_os = "wasi"

Based on tokio-rs#1395

Co-authored-by: Thomas de Zeeuw <thomasdezeeuw@gmail.com>
Signed-off-by: Harald Hoyer <harald@profian.com>

Cargo.toml

@@ -49,6 +49,10 @@ miow   = "0.3.6"
 winapi = { version = "0.3", features = ["winsock2", "mswsock"] }
 ntapi  = "0.3"
 
+[target.'cfg(target_os = "wasi")'.dependencies]
+wasi = "0.11.0"
+libc = "0.2.86"
+
 [dev-dependencies]
 env_logger = { version = "0.8.4", default-features = false }
 rand = "0.8"

src/io_source.rs

@@ -1,6 +1,8 @@
 use std::ops::{Deref, DerefMut};
 #[cfg(unix)]
 use std::os::unix::io::AsRawFd;
+#[cfg(target_os = "wasi")]
+use std::os::wasi::io::AsRawFd;
 #[cfg(windows)]
 use std::os::windows::io::AsRawSocket;
 #[cfg(debug_assertions)]
@@ -200,6 +202,44 @@ where
     }
 }
 
+#[cfg(target_os = "wasi")]
+impl<T> event::Source for IoSource<T>
+where
+    T: AsRawFd,
+{
+    fn register(
+        &mut self,
+        registry: &Registry,
+        token: Token,
+        interests: Interest,
+    ) -> io::Result<()> {
+        #[cfg(debug_assertions)]
+        self.selector_id.associate(registry)?;
+        registry
+            .selector()
+            .register(self.inner.as_raw_fd() as _, token, interests)
+    }
+
+    fn reregister(
+        &mut self,
+        registry: &Registry,
+        token: Token,
+        interests: Interest,
+    ) -> io::Result<()> {
+        #[cfg(debug_assertions)]
+        self.selector_id.check_association(registry)?;
+        registry
+            .selector()
+            .reregister(self.inner.as_raw_fd() as _, token, interests)
+    }
+
+    fn deregister(&mut self, registry: &Registry) -> io::Result<()> {
+        #[cfg(debug_assertions)]
+        self.selector_id.remove_association(registry)?;
+        registry.selector().deregister(self.inner.as_raw_fd() as _)
+    }
+}
+
 impl<T> fmt::Debug for IoSource<T>
 where
     T: fmt::Debug,

src/sys/mod.rs

@@ -63,6 +63,12 @@ cfg_os_poll! {
     pub use self::windows::*;
 }
 
+#[cfg(target_os = "wasi")]
+cfg_os_poll! {
+    mod wasi;
+    pub(crate) use self::wasi::*;
+}
+
 cfg_not_os_poll! {
     mod shell;
     pub(crate) use self::shell::*;