      1
      2
      3
      4
      5
      6
      7
      8
      9
     10
     11
     12
     13
     14
     15
     16
     17
     18
     19
     20
     21
     22
     23
     24
     25
     26
     27
     28
     29
     30
     31
     32
     33
     34
     35
     36
     37
     38
     39
     40
     41
     42
     43
     44
     45
     46
     47
     48
     49
     50
     51
     52
     53
     54
     55
     56
     57
     58
     59
     60
     61
     62
     63
     64
     65
     66
     67
     68
     69
     70
     71
     72
     73
     74
     75
     76
     77
     78
     79
     80
     81
     82
     83
     84
     85
     86
     87
     88
     89
     90
     91
     92
     93
     94
     95
     96
     97
     98
     99
    100
    101
    102
    103
    104
    105
    106
    107
    108
    109
    110
    111
    112
    113

    // Copyright 2012-2014 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.

    //! Exposes the NonZero lang item which provides optimization hints.
    #![unstable(feature = "nonzero",
                reason = "needs an RFC to flesh out the design",
                issue = "27730")]

    use ops::CoerceUnsized;

    /// Unsafe trait to indicate what types are usable with the NonZero struct
    pub unsafe trait Zeroable {
        /// Whether this value is zero
        fn is_zero(&self) -> bool;
    }

    macro_rules! impl_zeroable_for_pointer_types {
        ( $( $Ptr: ty )+ ) => {
            $(
                /// For fat pointers to be considered "zero", only the "data" part needs to be null.
                unsafe impl<T: ?Sized> Zeroable for $Ptr {
                    #[inline]
                    fn is_zero(&self) -> bool {
                        (*self).is_null()
                    }
                }
            )+
        }
    }

    macro_rules! impl_zeroable_for_integer_types {
        ( $( $Int: ty )+ ) => {
            $(
                unsafe impl Zeroable for $Int {
                    #[inline]
                    fn is_zero(&self) -> bool {
                        *self == 0
                    }
                }
            )+
        }
    }

    impl_zeroable_for_pointer_types! {
        *const T
        *mut T
    }

    impl_zeroable_for_integer_types! {
        usize u8 u16 u32 u64 u128
        isize i8 i16 i32 i64 i128
    }

    /// A wrapper type for raw pointers and integers that will never be
    /// NULL or 0 that might allow certain optimizations.
    #[lang = "non_zero"]
    #[derive(Copy, Clone, Eq, PartialEq, Ord, PartialOrd, Debug, Hash)]
    pub struct NonZero<T: Zeroable>(T);

    impl<T: Zeroable> NonZero<T> {
        /// Creates an instance of NonZero with the provided value.
        /// You must indeed ensure that the value is actually "non-zero".
        #[unstable(feature = "nonzero",
                   reason = "needs an RFC to flesh out the design",
                   issue = "27730")]
        #[inline]
        pub const unsafe fn new_unchecked(inner: T) -> Self {
            NonZero(inner)
        }

        /// Creates an instance of NonZero with the provided value.
        #[inline]
        pub fn new(inner: T) -> Option<Self> {
            if inner.is_zero() {
                None
            } else {
                Some(NonZero(inner))
            }
        }

        /// Gets the inner value.
        pub fn get(self) -> T {
            self.0
        }
    }

    impl<T: Zeroable+CoerceUnsized<U>, U: Zeroable> CoerceUnsized<NonZero<U>> for NonZero<T> {}

    impl<'a, T: ?Sized> From<&'a mut T> for NonZero<*mut T> {
        fn from(reference: &'a mut T) -> Self {
            NonZero(reference)
        }
    }

    impl<'a, T: ?Sized> From<&'a mut T> for NonZero<*const T> {
        fn from(reference: &'a mut T) -> Self {
            let ptr: *mut T = reference;
            NonZero(ptr)
        }
    }

    impl<'a, T: ?Sized> From<&'a T> for NonZero<*const T> {
        fn from(reference: &'a T) -> Self {
            NonZero(reference)
        }
    }

# Help

## Keyboard Shortcuts

`?`
  Show this help dialog
`S`
  Focus the search field
`↑`
  Move up in search results
`↓`
  Move down in search results
`↹`
  Switch tab
`⏎`
  Go to active search result
`+`
  Expand all sections
`-`
  Collapse all sections

## Search Tricks

Prefix searches with a type followed by a colon (e.g. `fn:`) to restrict the search to a given type.

Accepted types are: `fn`, `mod`, `struct`, `enum`, `trait`, `type`, `macro`, and `const`.

Search functions by type signature (e.g. `vec -> usize` or `* -> vec`)