From 698f8c2f01ea549d77d7dc3338a12e04c11057b9 Mon Sep 17 00:00:00 2001
From: Daniel Baumann <daniel.baumann@progress-linux.org>
Date: Wed, 17 Apr 2024 14:02:58 +0200
Subject: Adding upstream version 1.64.0+dfsg1.

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>
---
 library/std/src/sys_common/mutex.rs | 93 +++++++++++++++++++++++++++++++++++++
 1 file changed, 93 insertions(+)
 create mode 100644 library/std/src/sys_common/mutex.rs

(limited to 'library/std/src/sys_common/mutex.rs')

diff --git a/library/std/src/sys_common/mutex.rs b/library/std/src/sys_common/mutex.rs
new file mode 100644
index 000000000..48479f5bd
--- /dev/null
+++ b/library/std/src/sys_common/mutex.rs
@@ -0,0 +1,93 @@
+use crate::sys::locks as imp;
+
+/// An OS-based mutual exclusion lock, meant for use in static variables.
+///
+/// This mutex has a const constructor ([`StaticMutex::new`]), does not
+/// implement `Drop` to cleanup resources, and causes UB when used reentrantly.
+///
+/// This mutex does not implement poisoning.
+///
+/// This is a wrapper around `imp::Mutex` that does *not* call `init()` and
+/// `destroy()`.
+pub struct StaticMutex(imp::Mutex);
+
+unsafe impl Sync for StaticMutex {}
+
+impl StaticMutex {
+    /// Creates a new mutex for use.
+    #[inline]
+    pub const fn new() -> Self {
+        Self(imp::Mutex::new())
+    }
+
+    /// Calls raw_lock() and then returns an RAII guard to guarantee the mutex
+    /// will be unlocked.
+    ///
+    /// It is undefined behaviour to call this function while locked by the
+    /// same thread.
+    #[inline]
+    pub unsafe fn lock(&'static self) -> StaticMutexGuard {
+        self.0.lock();
+        StaticMutexGuard(&self.0)
+    }
+}
+
+#[must_use]
+pub struct StaticMutexGuard(&'static imp::Mutex);
+
+impl Drop for StaticMutexGuard {
+    #[inline]
+    fn drop(&mut self) {
+        unsafe {
+            self.0.unlock();
+        }
+    }
+}
+
+/// An OS-based mutual exclusion lock.
+///
+/// This mutex cleans up its resources in its `Drop` implementation, may safely
+/// be moved (when not borrowed), and does not cause UB when used reentrantly.
+///
+/// This mutex does not implement poisoning.
+///
+/// This is either a wrapper around `LazyBox<imp::Mutex>` or `imp::Mutex`,
+/// depending on the platform. It is boxed on platforms where `imp::Mutex` may
+/// not be moved.
+pub struct MovableMutex(imp::MovableMutex);
+
+unsafe impl Sync for MovableMutex {}
+
+impl MovableMutex {
+    /// Creates a new mutex.
+    #[inline]
+    pub const fn new() -> Self {
+        Self(imp::MovableMutex::new())
+    }
+
+    pub(super) fn raw(&self) -> &imp::Mutex {
+        &self.0
+    }
+
+    /// Locks the mutex blocking the current thread until it is available.
+    #[inline]
+    pub fn raw_lock(&self) {
+        unsafe { self.0.lock() }
+    }
+
+    /// Attempts to lock the mutex without blocking, returning whether it was
+    /// successfully acquired or not.
+    #[inline]
+    pub fn try_lock(&self) -> bool {
+        unsafe { self.0.try_lock() }
+    }
+
+    /// Unlocks the mutex.
+    ///
+    /// Behavior is undefined if the current thread does not actually hold the
+    /// mutex.
+    #[inline]
+    pub unsafe fn raw_unlock(&self) {
+        self.0.unlock()
+    }
+}
-- 
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