using std rwlock and spin on no_std environments

src/lib.rs

@@ -102,6 +102,8 @@
     html_logo_url = "https://raw.githubusercontent.com/smol-rs/smol/master/assets/images/logo_fullsize_transparent.png"
 )]
 
+mod rwlock;
+
 #[cfg(doctest)]
 mod doctests {
     doc_comment::doctest!("../README.md");
@@ -122,10 +124,10 @@ use core::future::Future;
 use core::marker::PhantomPinned;
 use core::pin::Pin;
 use core::task::{Context, Poll};
-use spin::RwLock;
 #[cfg(feature = "std")]
 use std::error;
 
+use crate::rwlock::RwLock;
 use event_listener::{Event, EventListener};
 use event_listener_strategy::{easy_wrapper, EventListenerFuture};
 use futures_core::{ready, stream::Stream};

src/rwlock.rs

@@ -0,0 +1,47 @@
+#[cfg(feature = "std")]
+#[derive(Debug)]
+pub(crate) struct RwLock<T> {
+    rwlock: std::sync::RwLock<T>,
+}
+#[cfg(not(feature = "std"))]
+#[derive(Debug)]
+pub(crate) struct RwLock<T> {
+    rwlock: spin::RwLock<T>,
+}
+
+impl<T> RwLock<T> {
+    #[cfg(feature = "std")]
+    #[inline]
+    pub(crate) const fn new(t: T) -> RwLock<T> {
+        return RwLock {
+            rwlock: std::sync::RwLock::new(t),
+        };
+    }
+    #[cfg(not(feature = "std"))]
+    #[inline]
+    pub(crate) const fn new(t: T) -> RwLock<T> {
+        return RwLock {
+            rwlock: spin::RwLock::new(t),
+        };
+    }
+    #[inline]
+    #[cfg(feature = "std")]
+    pub(crate) fn read(&self) -> std::sync::RwLockReadGuard<'_, T> {
+        return self.rwlock.read().unwrap();
+    }
+    #[inline]
+    #[cfg(not(feature = "std"))]
+    pub(crate) fn read(&self) -> spin::RwLockReadGuard<'_, T> {
+        return self.rwlock.read();
+    }
+    #[inline]
+    #[cfg(feature = "std")]
+    pub(crate) fn write(&self) -> std::sync::RwLockWriteGuard<'_, T> {
+        return self.rwlock.write().unwrap();
+    }
+    #[inline]
+    #[cfg(not(feature = "std"))]
+    pub(crate) fn write(&self) -> spin::RwLockWriteGuard<'_, T> {
+        return self.rwlock.write();
+    }
+}