Add TupleSlice trait to rustc_data_structures.

src/librustc_data_structures/lib.rs

@@ -42,6 +42,7 @@ pub mod snapshot_vec;
 pub mod transitive_relation;
 pub mod unify;
 pub mod fnv;
+pub mod tuple_slice;
 
 // See comments in src/librustc/lib.rs
 #[doc(hidden)]

src/librustc_data_structures/tuple_slice.rs

@@ -0,0 +1,60 @@
+// Copyright 2014 The Rust Project Developers. See the COPYRIGHT
+// file at the top-level directory of this distribution and at
+// http://rust-lang.org/COPYRIGHT.
+//
+// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
+// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
+// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
+// option. This file may not be copied, modified, or distributed
+// except according to those terms.
+
+use std::slice;
+
+/// Allows to view uniform tuples as slices
+pub trait TupleSlice<T> {
+    fn as_slice(&self) -> &[T];
+    fn as_mut_slice(&mut self) -> &mut [T];
+}
+
+macro_rules! impl_tuple_slice {
+    ($tuple_type:ty, $size:expr) => {
+        impl<T> TupleSlice<T> for $tuple_type {
+            fn as_slice(&self) -> &[T] {
+                unsafe {
+                    let ptr = &self.0 as *const T;
+                    slice::from_raw_parts(ptr, $size)
+                }
+            }
+
+            fn as_mut_slice(&mut self) -> &mut [T] {
+                unsafe {
+                    let ptr = &mut self.0 as *mut T;
+                    slice::from_raw_parts_mut(ptr, $size)
+                }
+            }
+        }
+    }
+}
+
+impl_tuple_slice!((T,T), 2);
+impl_tuple_slice!((T,T,T), 3);
+impl_tuple_slice!((T,T,T,T), 4);
+impl_tuple_slice!((T,T,T,T,T), 5);
+impl_tuple_slice!((T,T,T,T,T,T), 6);
+impl_tuple_slice!((T,T,T,T,T,T,T), 7);
+impl_tuple_slice!((T,T,T,T,T,T,T,T), 8);
+
+#[test]
+fn test_sliced_tuples() {
+    let t2 = (100i32, 101i32);
+    assert_eq!(t2.as_slice(), &[100i32, 101i32]);
+
+    let t3 = (102i32, 103i32, 104i32);
+    assert_eq!(t3.as_slice(), &[102i32, 103i32, 104i32]);
+
+    let t4 = (105i32, 106i32, 107i32, 108i32);
+    assert_eq!(t4.as_slice(), &[105i32, 106i32, 107i32, 108i32]);
+
+    let t5 = (109i32, 110i32, 111i32, 112i32, 113i32);
+    assert_eq!(t5.as_slice(), &[109i32, 110i32, 111i32, 112i32, 113i32]);
+}