From ef24de24a82fe681581cc130f342363c47c0969a Mon Sep 17 00:00:00 2001
From: Daniel Baumann <daniel.baumann@progress-linux.org>
Date: Fri, 7 Jun 2024 07:48:48 +0200
Subject: Merging upstream version 1.75.0+dfsg1.

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>
---
 vendor/gix-features-0.35.0/src/threading.rs | 110 ++++++++++++++++++++++++++++
 1 file changed, 110 insertions(+)
 create mode 100644 vendor/gix-features-0.35.0/src/threading.rs

(limited to 'vendor/gix-features-0.35.0/src/threading.rs')

diff --git a/vendor/gix-features-0.35.0/src/threading.rs b/vendor/gix-features-0.35.0/src/threading.rs
new file mode 100644
index 000000000..5f92ba2a8
--- /dev/null
+++ b/vendor/gix-features-0.35.0/src/threading.rs
@@ -0,0 +1,110 @@
+//! Type definitions for putting shared ownership and synchronized mutation behind the `threading` feature toggle.
+//!
+//! That way, single-threaded applications will not have to use thread-safe primitives, and simply do not specify the 'threading' feature.
+
+#[cfg(feature = "parallel")]
+mod _impl {
+    use std::sync::Arc;
+
+    /// A thread-safe cell which can be written to only once.
+    #[cfg(feature = "once_cell")]
+    pub type OnceCell<T> = once_cell::sync::OnceCell<T>;
+    /// A reference counted pointer type for shared ownership.
+    pub type OwnShared<T> = Arc<T>;
+    /// A synchronization primitive which can start read-only and transition to support mutation.
+    pub type MutableOnDemand<T> = parking_lot::RwLock<T>;
+    /// A synchronization primitive which provides read-write access right away.
+    pub type Mutable<T> = parking_lot::Mutex<T>;
+    /// A guarded reference suitable for safekeeping in a struct.
+    pub type RefGuard<'a, T> = parking_lot::RwLockReadGuard<'a, T>;
+    /// A mapped reference created from a `RefGuard`
+    pub type MappedRefGuard<'a, U> = parking_lot::MappedRwLockReadGuard<'a, U>;
+
+    /// Get a shared reference through a [`MutableOnDemand`] for read-only access.
+    pub fn get_ref<T>(v: &MutableOnDemand<T>) -> RefGuard<'_, T> {
+        v.read()
+    }
+
+    /// Get a mutable reference through a [`MutableOnDemand`] for read-write access.
+    pub fn get_mut<T>(v: &MutableOnDemand<T>) -> parking_lot::RwLockWriteGuard<'_, T> {
+        v.write()
+    }
+
+    /// Get a mutable reference to the underlying data, with semantics similar to [Arc::make_mut()].
+    pub fn make_mut<T: Clone>(this: &mut OwnShared<T>) -> &mut T {
+        OwnShared::make_mut(this)
+    }
+
+    /// Get a mutable reference through a [`Mutable`] for read-write access.
+    pub fn lock<T>(v: &Mutable<T>) -> parking_lot::MutexGuard<'_, T> {
+        v.lock()
+    }
+
+    /// Downgrade a handle previously obtained with [`get_mut()`] to drop mutation support.
+    pub fn downgrade_mut_to_ref<'a, T>(
+        v: parking_lot::RwLockWriteGuard<'a, T>,
+        _orig: &'a MutableOnDemand<T>,
+    ) -> RefGuard<'a, T> {
+        parking_lot::RwLockWriteGuard::downgrade(v)
+    }
+
+    /// Map a read guard into a sub-type it contains.
+    pub fn map_ref<T, U: ?Sized>(v: RefGuard<'_, T>, f: impl FnOnce(&T) -> &U) -> MappedRefGuard<'_, U> {
+        parking_lot::RwLockReadGuard::map(v, f)
+    }
+}
+
+#[cfg(not(feature = "parallel"))]
+mod _impl {
+    use std::{
+        cell::{Ref, RefCell, RefMut},
+        rc::Rc,
+    };
+
+    /// A thread-safe cell which can be written to only once.
+    #[cfg(feature = "once_cell")]
+    pub type OnceCell<T> = once_cell::unsync::OnceCell<T>;
+    /// A reference counted pointer type for shared ownership.
+    pub type OwnShared<T> = Rc<T>;
+    /// A synchronization primitive which can start read-only and transition to support mutation.
+    pub type MutableOnDemand<T> = RefCell<T>;
+    /// A synchronization primitive which provides read-write access right away.
+    pub type Mutable<T> = RefCell<T>;
+    /// A guarded reference suitable for safekeeping in a struct.
+    pub type RefGuard<'a, T> = Ref<'a, T>;
+    /// A mapped reference created from a RefGuard
+    pub type MappedRefGuard<'a, U> = Ref<'a, U>;
+
+    /// Get a shared reference through a [`MutableOnDemand`] for read-only access.
+    pub fn get_mut<T>(v: &RefCell<T>) -> RefMut<'_, T> {
+        v.borrow_mut()
+    }
+
+    /// Get a mutable reference to the underlying data, with semantics similar to [Rc::make_mut()].
+    pub fn make_mut<T: Clone>(this: &mut OwnShared<T>) -> &mut T {
+        OwnShared::make_mut(this)
+    }
+
+    /// Get a mutable reference through a [`Mutable`] for read-write access.
+    pub fn lock<T>(v: &Mutable<T>) -> RefMut<'_, T> {
+        v.borrow_mut()
+    }
+
+    /// Get a mutable reference through a [`MutableOnDemand`] for read-write access.
+    pub fn get_ref<T>(v: &RefCell<T>) -> RefGuard<'_, T> {
+        v.borrow()
+    }
+
+    /// Downgrade a handle previously obtained with [`upgrade_ref_to_mut()`] to drop mutation support.
+    pub fn downgrade_mut_to_ref<'a, T>(v: RefMut<'a, T>, orig: &'a RefCell<T>) -> RefGuard<'a, T> {
+        drop(v);
+        orig.borrow()
+    }
+
+    /// Map a read guard into a sub-type it contains.
+    pub fn map_ref<T, U: ?Sized>(v: RefGuard<'_, T>, f: impl FnOnce(&T) -> &U) -> MappedRefGuard<'_, U> {
+        Ref::map(v, f)
+    }
+}
+
+pub use _impl::*;
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