New design based on *mut T

Cargo.toml

@@ -13,11 +13,16 @@ repository = "https://github.com/rust-osdev/volatile"
 [features]
 # Enable unstable features; requires Rust nightly; might break on compiler updates
 unstable = []
+# Enable unstable and experimental features; requires Rust nightly; might break on compiler updates
+very_unstable = ["unstable"]
+
+[dev-dependencies]
+rand = "0.8.3"
 
 [package.metadata.release]
 no-dev-version = true
 pre-release-replacements = [
-    { file="Changelog.md", search="# Unreleased", replace="# Unreleased\n\n# {{version}} – {{date}}", exactly=1 },
+    { file = "Changelog.md", search = "# Unreleased", replace = "# Unreleased\n\n# {{version}} – {{date}}", exactly = 1 },
 ]
 pre-release-commit-message = "Release version {{version}}"
 

src/access.rs

@@ -1,22 +1,48 @@
-/// Helper trait that is implemented by [`ReadWrite`] and [`ReadOnly`].
-pub trait Readable {}
+#[derive(Debug, Clone, Copy, PartialEq, Eq, Default)]
+pub struct NoAccess;
 
-/// Helper trait that is implemented by [`ReadWrite`] and [`WriteOnly`].
-pub trait Writable {}
+#[derive(Debug, Clone, Copy, PartialEq, Eq, Default)]
+pub struct UnsafeAccess;
 
-/// Zero-sized marker type for allowing both read and write access.
-#[derive(Debug, Copy, Clone)]
-pub struct ReadWrite;
-impl Readable for ReadWrite {}
-impl Writable for ReadWrite {}
+#[derive(Debug, Clone, Copy, PartialEq, Eq, Default)]
+pub struct SafeAccess;
 
-/// Zero-sized marker type for allowing only read access.
-#[derive(Debug, Copy, Clone)]
-pub struct ReadOnly;
+pub trait Unsafe {}
+pub trait Safe: Unsafe {}
 
-impl Readable for ReadOnly {}
+impl Unsafe for UnsafeAccess {}
+impl Unsafe for SafeAccess {}
+impl Safe for SafeAccess {}
 
-/// Zero-sized marker type for allowing only write access.
-#[derive(Debug, Copy, Clone)]
-pub struct WriteOnly;
-impl Writable for WriteOnly {}
+#[derive(Debug, Clone, Copy, PartialEq, Eq)]
+pub struct Access<R, W> {
+    pub read: R,
+    pub write: W,
+}
+
+impl Access<SafeAccess, NoAccess> {
+    pub const fn read_only() -> ReadOnly {
+        Access {
+            read: SafeAccess,
+            write: NoAccess,
+        }
+    }
+
+    pub const fn write_only() -> WriteOnly {
+        Access {
+            read: NoAccess,
+            write: SafeAccess,
+        }
+    }
+
+    pub const fn read_write() -> ReadWrite {
+        Access {
+            read: SafeAccess,
+            write: SafeAccess,
+        }
+    }
+}
+
+pub type ReadOnly = Access<SafeAccess, NoAccess>;
+pub type WriteOnly = Access<NoAccess, SafeAccess>;
+pub type ReadWrite = Access<SafeAccess, SafeAccess>;