1 files changed, 44 insertions, 0 deletions
diff --git a/vendor/mac/src/mem.rs b/vendor/mac/src/mem.rs
new file mode 100644
index 000000000..49cf5f1b1
--- /dev/null
+++ b/vendor/mac/src/mem.rs
@@ -0,0 +1,44 @@
+//! Macros for low-level memory manipulation.
+
+/// Make a tuple of the addresses of some of a struct's fields.
+///
+/// This is useful when you are transmuting between struct types
+/// and would like an additional dynamic check that the layouts
+/// match. It's difficult to make such an assertion statically
+/// in Rust at present.
+///
+/// # Example
+///
+/// ```
+/// # #[macro_use] extern crate mac;
+/// use std::mem;
+///
+/// # fn main() {
+/// struct Foo { x: i32, y: i32 }
+/// struct Bar { x: u32, y: u32 }
+///
+/// let foo = Foo { x: 3, y: 4 };
+/// let old_addrs = addrs_of!(foo => x, y);
+///
+/// let bar = unsafe {
+///     mem::transmute::<&Foo, &Bar>(&foo)
+/// };
+/// let new_addrs = addrs_of!(bar => x, y);
+/// assert_eq!(old_addrs, new_addrs);
+///
+/// assert_eq!(bar.x, 3);
+/// assert_eq!(bar.y, 4);
+/// # }
+/// ```
+#[macro_export]
+macro_rules! addrs_of {
+    ($obj:expr => $($field:ident),+) => {
+        ( // make a tuple
+            $(
+                unsafe {
+                    ::std::mem::transmute::<_, usize>(&$obj.$field)
+                }
+            ),+
+        )
+    }
+}