From 997805ff5b8ce93cc4c87cc38b15e4883c4f07e1 Mon Sep 17 00:00:00 2001
From: Philipp Oppermann <dev@phil-opp.com>
Date: Wed, 23 Dec 2020 12:12:30 +0100
Subject: [PATCH 1/2] Add methods to restrict access

---
 src/lib.rs | 49 +++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 49 insertions(+)

diff --git a/src/lib.rs b/src/lib.rs
index 54d103d..a359377 100644
--- a/src/lib.rs
+++ b/src/lib.rs
@@ -746,6 +746,55 @@ where
     }
 }
 
+/// Methods for restricting access.
+impl<R> Volatile<R> {
+    /// Restricts access permissions to read-only.
+    ///
+    /// ## Example
+    ///
+    /// ```
+    /// use volatile::Volatile;
+    ///
+    /// let mut value: i16 = -4;
+    /// let mut volatile = Volatile::new(&mut value);
+    ///
+    /// let read_only = volatile.read_only();
+    /// assert_eq!(read_only.read(), -4);
+    /// // read_only.write(10); // compile-time error
+    /// ```
+    pub fn read_only(self) -> Volatile<R, ReadOnly> {
+        Volatile {
+            reference: self.reference,
+            access: PhantomData,
+        }
+    }
+
+    /// Restricts access permissions to write-only.
+    ///
+    /// ## Example
+    ///
+    /// Creating a write-only reference to a struct field:
+    ///
+    /// ```
+    /// use volatile::Volatile;
+    ///
+    /// struct Example { field_1: u32, field_2: u8, }
+    /// let mut value = Example { field_1: 15, field_2: 255 };
+    /// let mut volatile = Volatile::new(&mut value);
+    ///
+    /// // construct a volatile write-only reference to `field_2`
+    /// let mut field_2 = volatile.map_mut(|example| &mut example.field_2).write_only();
+    /// field_2.write(14);
+    /// // field_2.read(); // compile-time error
+    /// ```
+    pub fn write_only(self) -> Volatile<R, WriteOnly> {
+        Volatile {
+            reference: self.reference,
+            access: PhantomData,
+        }
+    }
+}
+
 impl<R, T, A> fmt::Debug for Volatile<R, A>
 where
     R: Deref<Target = T>,

From aca085fe2233b2da3cf85768478cd55c2b7e68b1 Mon Sep 17 00:00:00 2001
From: Philipp Oppermann <dev@phil-opp.com>
Date: Wed, 23 Dec 2020 12:39:05 +0100
Subject: [PATCH 2/2] Update changelog for #19

---
 Changelog.md | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/Changelog.md b/Changelog.md
index 229bc1a..6f149f6 100644
--- a/Changelog.md
+++ b/Changelog.md
@@ -1,5 +1,7 @@
 # Unreleased
 
+- Add methods to restrict access ([#19](https://github.com/rust-osdev/volatile/pull/19))
+
 # 0.4.2 – 2020-10-31
 
 - Change `slice::check_range` to `RangeBounds::assert_len` ([#16](https://github.com/rust-osdev/volatile/pull/16))