1 files changed, 96 insertions, 0 deletions
diff --git a/third_party/rust/plain/src/plain.rs b/third_party/rust/plain/src/plain.rs
new file mode 100644
index 0000000000..35522006de
--- /dev/null
+++ b/third_party/rust/plain/src/plain.rs
@@ -0,0 +1,96 @@
+use Error;
+
+/// A trait for plain data types that can be safely read from a byte slice.
+///
+/// A type can be [`Plain`](trait.Plain.html) if it is `#repr(C)` and only contains
+/// data with no possible invalid values. Types that _can't_ be `Plain`
+/// include, but are not limited to, `bool`, `char`, `enum`s, tuples,
+/// pointers and references.
+///
+/// At this moment, `Drop` types are also not legal, because
+/// compiler adds a special "drop flag" into the type. This is slated
+/// to change in the future.
+///
+/// On the other hand, arrays of a `Plain` type, and
+/// structures where all members are plain (and not `Drop`), are okay.
+///
+/// Structures that are not `#repr(C)`, while not necessarily illegal
+/// in principle, are largely useless because they don't have a stable
+/// layout. For example, the compiler is allowed to reorder fields
+/// arbitrarily.
+///
+/// All methods of this trait are implemented automatically as wrappers
+/// for crate-level funtions.
+///
+pub unsafe trait Plain {
+    #[inline(always)]
+    fn from_bytes(bytes: &[u8]) -> Result<&Self, Error>
+    where
+        Self: Sized,
+    {
+        ::from_bytes(bytes)
+    }
+
+    #[inline(always)]
+    fn slice_from_bytes(bytes: &[u8]) -> Result<&[Self], Error>
+    where
+        Self: Sized,
+    {
+        ::slice_from_bytes(bytes)
+    }
+
+    #[inline(always)]
+    fn slice_from_bytes_len(bytes: &[u8], len: usize) -> Result<&[Self], Error>
+    where
+        Self: Sized,
+    {
+        ::slice_from_bytes_len(bytes, len)
+    }
+
+    #[inline(always)]
+    fn from_mut_bytes(bytes: &mut [u8]) -> Result<&mut Self, Error>
+    where
+        Self: Sized,
+    {
+        ::from_mut_bytes(bytes)
+    }
+
+    #[inline(always)]
+    fn slice_from_mut_bytes(bytes: &mut [u8]) -> Result<&mut [Self], Error>
+    where
+        Self: Sized,
+    {
+        ::slice_from_mut_bytes(bytes)
+    }
+
+    #[inline(always)]
+    fn slice_from_mut_bytes_len(bytes: &mut [u8], len: usize) -> Result<&mut [Self], Error>
+    where
+        Self: Sized,
+    {
+        ::slice_from_mut_bytes_len(bytes, len)
+    }
+
+    #[inline(always)]
+    fn copy_from_bytes(&mut self, bytes: &[u8]) -> Result<(), Error> {
+        ::copy_from_bytes(self, bytes)
+    }
+}
+
+unsafe impl Plain for u8 {}
+unsafe impl Plain for u16 {}
+unsafe impl Plain for u32 {}
+unsafe impl Plain for u64 {}
+unsafe impl Plain for usize {}
+
+unsafe impl Plain for i8 {}
+unsafe impl Plain for i16 {}
+unsafe impl Plain for i32 {}
+unsafe impl Plain for i64 {}
+unsafe impl Plain for isize {}
+
+unsafe impl<S> Plain for [S]
+where
+    S: Plain,
+{
+}