libcore: Add NonZero lang item and implement some methods.

Author: luqmana

src/libcore/ptr.rs

@@ -101,6 +101,13 @@ pub use intrinsics::copy_memory;
 pub use intrinsics::copy_nonoverlapping_memory;
 pub use intrinsics::set_memory;
 
+
+/// A wrapper type for raw pointers and integers that will never be
+/// NULL or 0 that might allow certain optimizations.
+#[lang="non_zero"]
+#[deriving(Clone, PartialEq, Eq, PartialOrd)]
+pub struct NonZero<T>(pub T);
+
 /// Create a null pointer.
 ///
 /// # Example
@@ -264,6 +271,32 @@ impl<T> RawPtr<T> for *const T {
     }
 }
 
+impl<T> RawPtr<T> for NonZero<*const T> {
+    #[inline]
+    fn null() -> NonZero<*const T> { NonZero(null()) }
+
+    #[inline]
+    fn is_null(&self) -> bool { false }
+
+    #[inline]
+    fn to_uint(&self) -> uint {
+        let NonZero(p) = *self;
+        p as uint
+    }
+
+    #[inline]
+    unsafe fn offset(self, count: int) -> NonZero<*const T> {
+        let NonZero(p) = self;
+        NonZero(intrinsics::offset(p, count))
+    }
+
+    #[inline]
+    unsafe fn as_ref<'a>(&self) -> Option<&'a T> {
+        let NonZero(p) = *self;
+        Some(&*p)
+    }
+}
+
 impl<T> RawPtr<T> for *mut T {
     #[inline]
     fn null() -> *mut T { null_mut() }
@@ -289,6 +322,32 @@ impl<T> RawPtr<T> for *mut T {
     }
 }
 
+impl<T> RawPtr<T> for NonZero<*mut T> {
+    #[inline]
+    fn null() -> NonZero<*mut T> { NonZero(null_mut()) }
+
+    #[inline]
+    fn is_null(&self) -> bool { false }
+
+    #[inline]
+    fn to_uint(&self) -> uint {
+        let NonZero(p) = *self;
+        p as uint
+    }
+
+    #[inline]
+    unsafe fn offset(self, count: int) -> NonZero<*mut T> {
+        let NonZero(p) = self;
+        NonZero(intrinsics::offset(p as *const T, count) as *mut T)
+    }
+
+    #[inline]
+    unsafe fn as_ref<'a>(&self) -> Option<&'a T> {
+        let NonZero(p) = *self;
+        Some(&*p)
+    }
+}
+
 impl<T> RawMutPtr<T> for *mut T {
     #[inline]
     unsafe fn as_mut<'a>(&self) -> Option<&'a mut T> {
@@ -300,6 +359,14 @@ impl<T> RawMutPtr<T> for *mut T {
     }
 }
 
+impl<T> RawMutPtr<T> for NonZero<*mut T> {
+    #[inline]
+    unsafe fn as_mut<'a>(&self) -> Option<&'a mut T> {
+        let NonZero(p) = *self;
+        Some(&mut *p)
+    }
+}
+
 // Equality for pointers
 impl<T> PartialEq for *const T {
     #[inline]