libcore: add vec::{mut_view, const_view}.

src/libcore/vec.rs

@@ -27,7 +27,7 @@
 export last;
 export last_opt;
 export slice;
-export view;
+export view, mut_view, const_view;
 export split;
 export splitn;
 export rsplit;
@@ -325,6 +325,30 @@ fn reserve_at_least<T>(&v: ~[const T], n: uint) {
     }
 }
 
+/// Return a slice that points into another slice.
+pure fn mut_view<T>(v: &[mut T], start: uint, end: uint) -> &[mut T] {
+    assert (start <= end);
+    assert (end <= len(v));
+    do unpack_slice(v) |p, _len| {
+        unsafe {
+            ::unsafe::reinterpret_cast(
+                (ptr::offset(p, start), (end - start) * sys::size_of::<T>()))
+        }
+    }
+}
+
+/// Return a slice that points into another slice.
+pure fn const_view<T>(v: &[const T], start: uint, end: uint) -> &[const T] {
+    assert (start <= end);
+    assert (end <= len(v));
+    do unpack_slice(v) |p, _len| {
+        unsafe {
+            ::unsafe::reinterpret_cast(
+                (ptr::offset(p, start), (end - start) * sys::size_of::<T>()))
+        }
+    }
+}
+
 /// Split the vector `v` by applying each element against the predicate `f`.
 fn split<T: copy>(v: &[T], f: fn(T) -> bool) -> ~[~[T]] {
     let ln = len(v);