From 90dc513458c16af021717181fc45e27d8071c39c Mon Sep 17 00:00:00 2001
From: John Nunley <dev@notgull.net>
Date: Tue, 14 Nov 2023 20:06:19 -0800
Subject: [PATCH] bugfix: Use async-lock as the locking mechanism

We can't use `std::sync::Mutex` without further unsafe code, and we
can't use `simple-mutex` since it is unmaintained. Therefore we use the
`async-lock` crate, since it has a good blocking mutex.

Closes #12

Signed-off-by: John Nunley <dev@notgull.net>
---
 .github/workflows/ci.yml |  2 +-
 Cargo.toml               |  3 ++-
 src/lib.rs               | 46 ++++++++++++++++++++++++++--------------
 3 files changed, 33 insertions(+), 18 deletions(-)

diff --git a/.github/workflows/ci.yml b/.github/workflows/ci.yml
index 6082200..bc49288 100644
--- a/.github/workflows/ci.yml
+++ b/.github/workflows/ci.yml
@@ -49,7 +49,7 @@ jobs:
       matrix:
         # When updating this, the reminder to update the minimum supported
         # Rust version in Cargo.toml.
-        rust: ['1.41.0']
+        rust: ['1.59.0']
     steps:
       - uses: actions/checkout@v4
       - name: Install Rust
diff --git a/Cargo.toml b/Cargo.toml
index 58386f2..e2a88c7 100644
--- a/Cargo.toml
+++ b/Cargo.toml
@@ -6,7 +6,7 @@ name = "async-dup"
 version = "1.2.3"
 authors = ["Stjepan Glavina <stjepang@gmail.com>"]
 edition = "2018"
-rust-version = "1.41"
+rust-version = "1.59"
 description = "Duplicate an async I/O handle"
 license = "Apache-2.0 OR MIT"
 repository = "https://github.com/smol-rs/async-dup"
@@ -17,6 +17,7 @@ categories = ["asynchronous", "concurrency"]
 exclude = ["/.*"]
 
 [dependencies]
+async-lock = "3.1.0"
 futures-io = "0.3.5"
 
 [dev-dependencies]
diff --git a/src/lib.rs b/src/lib.rs
index 2b5db2f..2c6338a 100644
--- a/src/lib.rs
+++ b/src/lib.rs
@@ -60,7 +60,6 @@ use std::hash::{Hash, Hasher};
 use std::io::{self, IoSlice, IoSliceMut, SeekFrom};
 use std::ops::{Deref, DerefMut};
 use std::pin::Pin;
-use std::sync::TryLockError;
 use std::task::{Context, Poll};
 
 use futures_io::{AsyncRead, AsyncSeek, AsyncWrite};
@@ -227,7 +226,7 @@ where
 /// - `impl<T> AsyncWrite for &Mutex<T> where T: AsyncWrite + Unpin {}`
 /// - `impl<T> AsyncSeek for Mutex<T> where T: AsyncSeek + Unpin {}`
 /// - `impl<T> AsyncSeek for &Mutex<T> where T: AsyncSeek + Unpin {}`
-pub struct Mutex<T>(std::sync::Mutex<T>);
+pub struct Mutex<T>(async_lock::Mutex<T>);
 
 impl<T> Mutex<T> {
     /// Creates a new mutex.
@@ -257,7 +256,7 @@ impl<T> Mutex<T> {
     /// assert_eq!(*guard, 10);
     /// ```
     pub fn lock(&self) -> MutexGuard<'_, T> {
-        MutexGuard(self.0.lock().unwrap_or_else(|e| e.into_inner()))
+        MutexGuard(self.0.lock_blocking())
     }
 
     /// Attempts to acquire the mutex.
@@ -279,16 +278,7 @@ impl<T> Mutex<T> {
     /// # ;
     /// ```
     pub fn try_lock(&self) -> Option<MutexGuard<'_, T>> {
-        self.0
-            .try_lock()
-            .map_or_else(
-                |e| match e {
-                    TryLockError::Poisoned(e) => Some(e.into_inner()),
-                    TryLockError::WouldBlock => None,
-                },
-                Some,
-            )
-            .map(MutexGuard)
+        self.0.try_lock().map(MutexGuard)
     }
 
     /// Consumes the mutex, returning the underlying data.
@@ -302,7 +292,7 @@ impl<T> Mutex<T> {
     /// assert_eq!(mutex.into_inner(), 10);
     /// ```
     pub fn into_inner(self) -> T {
-        self.0.into_inner().unwrap_or_else(|e| e.into_inner())
+        self.0.into_inner()
     }
 
     /// Returns a mutable reference to the underlying data.
@@ -320,7 +310,7 @@ impl<T> Mutex<T> {
     /// assert_eq!(*mutex.lock(), 10);
     /// ```
     pub fn get_mut(&mut self) -> &mut T {
-        self.0.get_mut().unwrap_or_else(|e| e.into_inner())
+        self.0.get_mut()
     }
 }
 
@@ -461,7 +451,7 @@ impl<T: AsyncSeek + Unpin> AsyncSeek for &Mutex<T> {
 }
 
 /// A guard that releases the mutex when dropped.
-pub struct MutexGuard<'a, T>(std::sync::MutexGuard<'a, T>);
+pub struct MutexGuard<'a, T>(async_lock::MutexGuard<'a, T>);
 
 impl<T: fmt::Debug> fmt::Debug for MutexGuard<'_, T> {
     fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
@@ -488,3 +478,27 @@ impl<T> DerefMut for MutexGuard<'_, T> {
         &mut self.0
     }
 }
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    fn is_send<T: Send>(_: &T) {}
+    fn is_sync<T: Sync>(_: &T) {}
+
+    #[test]
+    fn is_send_sync() {
+        let arc = Arc::new(());
+        let mutex = Mutex::new(());
+
+        is_send(&arc);
+        is_sync(&arc);
+
+        is_send(&mutex);
+        is_sync(&mutex);
+
+        let guard = mutex.lock();
+        is_send(&guard);
+        is_sync(&guard);
+    }
+}