alnyan/yggdrasil: add FileMapping

library/std/src/os/yggdrasil/io/mod.rs

@@ -32,12 +32,64 @@ pub use raw::*;
 #[unstable(feature = "yggdrasil_os", issue = "none")]
 pub use poll::PollChannel;
 
+#[unstable(feature = "yggdrasil_os", issue = "none")]
+pub struct FileMapping<'a> {
+    data: &'a mut [u8],
+    _fd: OwnedFd,
+}
+
 #[unstable(feature = "yggdrasil_os", issue = "none")]
 pub trait FdDeviceRequest {
     #[unstable(feature = "yggdrasil_os", issue = "none")]
     unsafe fn device_request(&self, req: &mut DeviceRequest) -> crate::io::Result<()>;
 }
 
+#[unstable(feature = "yggdrasil_os", issue = "none")]
+impl<'a> FileMapping<'a> {
+    pub fn new<F: Into<OwnedFd>>(f: F, offset: u64, len: usize) -> crate::io::Result<Self> {
+        use yggdrasil_rt::mem::MappingSource;
+
+        let owned_fd = f.into();
+        let raw_fd = owned_fd.as_raw_fd();
+        let base = cvt_io(unsafe {
+            yggdrasil_rt::sys::map_memory(None, len, &MappingSource::File(raw_fd, offset))
+        })?;
+
+        #[allow(fuzzy_provenance_casts)]
+        let data = unsafe { crate::slice::from_raw_parts_mut(base as *mut u8, len) };
+
+        Ok(Self { data, _fd: owned_fd })
+    }
+}
+
+#[unstable(feature = "yggdrasil_os", issue = "none")]
+impl crate::ops::Deref for FileMapping<'_> {
+    type Target = [u8];
+
+    fn deref(&self) -> &Self::Target {
+        self.data
+    }
+}
+
+#[unstable(feature = "yggdrasil_os", issue = "none")]
+impl crate::ops::DerefMut for FileMapping<'_> {
+    fn deref_mut(&mut self) -> &mut Self::Target {
+        self.data
+    }
+}
+
+#[unstable(feature = "yggdrasil_os", issue = "none")]
+impl Drop for FileMapping<'_> {
+    fn drop(&mut self) {
+        // Unmap the memory
+        let base = self.data.as_ptr() as usize;
+        let len = self.data.len();
+        unsafe {
+            yggdrasil_rt::sys::unmap_memory(base, len).expect("Memory unmap failed");
+        }
+    }
+}
+
 #[unstable(feature = "yggdrasil_os", issue = "none")]
 impl<T: AsRawFd> FdDeviceRequest for T {
     unsafe fn device_request(&self, req: &mut DeviceRequest) -> crate::io::Result<()> {