      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
    114
    115
    116

    use core::fmt;
    use core::ops::{Deref, DerefMut};

    /// Pads and aligns a value to the length of a cache line.
    ///
    /// In concurrent programming, sometimes it is desirable to make sure commonly accessed pieces of
    /// data are not placed into the same cache line. Updating an atomic value invalides the whole
    /// cache line it belongs to, which makes the next access to the same cache line slower for other
    /// CPU cores. Use `CachePadded` to ensure updating one piece of data doesn't invalidate other
    /// cached data.
    ///
    /// Cache lines are assumed to be 64 bytes on all architectures.
    ///
    /// # Size and alignment
    ///
    /// The size of `CachePadded<T>` is the smallest multiple of 64 bytes large enough to accommodate
    /// a value of type `T`.
    ///
    /// The alignment of `CachePadded<T>` is the maximum of 64 bytes and the alignment of `T`.
    ///
    /// # Examples
    ///
    /// Alignment and padding:
    ///
    /// ```
    /// use crossbeam_utils::CachePadded;
    ///
    /// let array = [CachePadded::new(1i32), CachePadded::new(2i32)];
    /// let addr1 = &*array[0] as *const i32 as usize;
    /// let addr2 = &*array[1] as *const i32 as usize;
    ///
    /// assert_eq!(addr2 - addr1, 64);
    /// assert_eq!(addr1 % 64, 0);
    /// assert_eq!(addr2 % 64, 0);
    /// ```
    ///
    /// When building a concurrent queue with a head and a tail index, it is wise to place them in
    /// different cache lines so that concurrent threads pushing and popping elements don't invalidate
    /// each other's cache lines:
    ///
    /// ```
    /// use crossbeam_utils::CachePadded;
    /// use std::sync::atomic::AtomicUsize;
    ///
    /// struct Queue<T> {
    ///     head: CachePadded<AtomicUsize>,
    ///     tail: CachePadded<AtomicUsize>,
    ///     buffer: *mut T,
    /// }
    /// ```
    #[derive(Clone, Copy, Default, Hash, PartialEq, Eq)]
    #[repr(align(64))]
    pub struct CachePadded<T> {
        value: T,
    }

    unsafe impl<T: Send> Send for CachePadded<T> {}
    unsafe impl<T: Sync> Sync for CachePadded<T> {}

    impl<T> CachePadded<T> {
        /// Pads and aligns a value to the length of a cache line.
        ///
        /// # Examples
        ///
        /// ```
        /// use crossbeam_utils::CachePadded;
        ///
        /// let padded_value = CachePadded::new(1);
        /// ```
        pub fn new(t: T) -> CachePadded<T> {
            CachePadded::<T> { value: t }
        }

        /// Returns the value value.
        ///
        /// # Examples
        ///
        /// ```
        /// use crossbeam_utils::CachePadded;
        ///
        /// let padded_value = CachePadded::new(7);
        /// let value = padded_value.into_inner();
        /// assert_eq!(value, 7);
        /// ```
        pub fn into_inner(self) -> T {
            self.value
        }
    }

    impl<T> Deref for CachePadded<T> {
        type Target = T;

        fn deref(&self) -> &T {
            &self.value
        }
    }

    impl<T> DerefMut for CachePadded<T> {
        fn deref_mut(&mut self) -> &mut T {
            &mut self.value
        }
    }

    impl<T: fmt::Debug> fmt::Debug for CachePadded<T> {
        fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
            f.debug_struct("CachePadded")
                .field("value", &self.value)
                .finish()
        }
    }

    impl<T> From<T> for CachePadded<T> {
        fn from(t: T) -> Self {
            CachePadded::new(t)
        }
    }

# 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`)

Search multiple things at once by splitting your query with comma (e.g., `str,u8` or `String,struct:Vec,test`)