Introduce XArray and refactor the COW mechanism of Vmo

framework/aster-frame/src/collections/mod.rs

@@ -0,0 +1,4 @@
+// SPDX-License-Identifier: MPL-2.0
+
+//! This module provides some advanced collections.
+pub mod xarray;

framework/aster-frame/src/collections/xarray.rs

@@ -0,0 +1,51 @@
+// SPDX-License-Identifier: MPL-2.0
+
+//! This module introduces the xarray crate and provides relevant support and interfaces for `XArray`.
+extern crate xarray as xarray_crate;
+
+use alloc::sync::Arc;
+use core::{marker::PhantomData, mem::ManuallyDrop, ops::Deref};
+
+use xarray_crate::ItemEntry;
+pub use xarray_crate::{Cursor, CursorMut, XArray, XMark};
+
+use crate::vm::VmFrame;
+
+/// `VmFrameRef` is a struct that can work as `&'a VmFrame`.
+pub struct VmFrameRef<'a> {
+    inner: ManuallyDrop<VmFrame>,
+    _marker: PhantomData<&'a VmFrame>,
+}
+
+impl<'a> Deref for VmFrameRef<'a> {
+    type Target = VmFrame;
+
+    fn deref(&self) -> &Self::Target {
+        &self.inner
+    }
+}
+
+// SAFETY: `VmFrame` is essentially an `Arc` smart pointer that points to a location which is aligned to 4,
+// meeting the requirements of the `ItemEntry` for `XArray`.
+unsafe impl ItemEntry for VmFrame {
+    type Ref<'a> = VmFrameRef<'a> where Self: 'a;
+
+    fn into_raw(self) -> *const () {
+        let ptr = Arc::as_ptr(&self.frame_index);
+        let _ = ManuallyDrop::new(self);
+        ptr.cast()
+    }
+
+    unsafe fn from_raw(raw: *const ()) -> Self {
+        Self {
+            frame_index: Arc::from_raw(raw.cast()),
+        }
+    }
+
+    unsafe fn raw_as_ref<'a>(raw: *const ()) -> Self::Ref<'a> {
+        VmFrameRef {
+            inner: ManuallyDrop::new(VmFrame::from_raw(raw.cast())),
+            _marker: PhantomData,
+        }
+    }
+}

framework/aster-frame/src/lib.rs

@@ -28,6 +28,7 @@ extern crate static_assertions;
 pub mod arch;
 pub mod boot;
 pub mod bus;
+pub mod collections;
 pub mod console;
 pub mod cpu;
 mod error;