src/libcore/nonzero.rs

   1 // Copyright 2012-2014 The Rust Project Developers. See the COPYRIGHT
   2 // file at the top-level directory of this distribution and at
   3 // http://rust-lang.org/COPYRIGHT.
   4 //
   5 // Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
   6 // http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
   7 // <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
   8 // option. This file may not be copied, modified, or distributed
   9 // except according to those terms.
  10
  11 //! Exposes the NonZero lang item which provides optimization hints.
  12 #![unstable(feature = "nonzero",
  13             reason = "needs an RFC to flesh out the design",
  14             issue = "27730")]
  15
  16 use ops::{CoerceUnsized, Deref};
  17
  18 /// Unsafe trait to indicate what types are usable with the NonZero struct
  19 pub unsafe trait Zeroable {}
  20
  21 unsafe impl<T:?Sized> Zeroable for *const T {}
  22 unsafe impl<T:?Sized> Zeroable for *mut T {}
  23 unsafe impl Zeroable for isize {}
  24 unsafe impl Zeroable for usize {}
  25 unsafe impl Zeroable for i8 {}
  26 unsafe impl Zeroable for u8 {}
  27 unsafe impl Zeroable for i16 {}
  28 unsafe impl Zeroable for u16 {}
  29 unsafe impl Zeroable for i32 {}
  30 unsafe impl Zeroable for u32 {}
  31 unsafe impl Zeroable for i64 {}
  32 unsafe impl Zeroable for u64 {}
  33
  34 /// A wrapper type for raw pointers and integers that will never be
  35 /// NULL or 0 that might allow certain optimizations.
  36 #[lang = "non_zero"]
  37 #[derive(Copy, Clone, Eq, PartialEq, Ord, PartialOrd, Debug, Hash)]
  38 pub struct NonZero<T: Zeroable>(T);
  39
  40 impl<T: Zeroable> NonZero<T> {
  41     /// Creates an instance of NonZero with the provided value.
  42     /// You must indeed ensure that the value is actually "non-zero".
  43     #[inline(always)]
  44     pub const unsafe fn new(inner: T) -> NonZero<T> {
  45         NonZero(inner)
  46     }
  47 }
  48
  49 impl<T: Zeroable> Deref for NonZero<T> {
  50     type Target = T;
  51
  52     #[inline]
  53     fn deref(&self) -> &T {
  54         let NonZero(ref inner) = *self;
  55         inner
  56     }
  57 }
  58
  59 impl<T: Zeroable+CoerceUnsized<U>, U: Zeroable> CoerceUnsized<NonZero<U>> for NonZero<T> {}