      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
    117
    118
    119
    120
    121
    122
    123
    124
    125
    126
    127
    128
    129
    130
    131
    132
    133
    134
    135
    136
    137
    138
    139
    140
    141
    142
    143
    144
    145
    146
    147
    148
    149
    150
    151
    152
    153
    154
    155
    156
    157
    158
    159
    160
    161
    162
    163
    164
    165
    166
    167
    168
    169
    170
    171
    172
    173
    174
    175
    176
    177
    178
    179
    180

    use std::marker::PhantomData;
    use std::mem;
    use std::ptr;
    use std::sync::atomic::{self, Ordering};

    use super::{Owned, Shared, Guard};

    /// Like `std::sync::atomic::AtomicPtr`.
    ///
    /// Provides atomic access to a (nullable) pointer of type `T`, interfacing with
    /// the `Owned` and `Shared` types.
    pub struct Atomic<T> {
        ptr: atomic::AtomicPtr<T>,
        _marker: PhantomData<*const ()>,
    }

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

    fn opt_shared_into_raw<T>(val: Option<Shared<T>>) -> *mut T {
        val.map(|p| p.as_raw()).unwrap_or(ptr::null_mut())
    }

    fn opt_owned_as_raw<T>(val: &Option<Owned<T>>) -> *mut T {
        val.as_ref().map(Owned::as_raw).unwrap_or(ptr::null_mut())
    }

    fn opt_owned_into_raw<T>(val: Option<Owned<T>>) -> *mut T {
        let ptr = val.as_ref().map(Owned::as_raw).unwrap_or(ptr::null_mut());
        mem::forget(val);
        ptr
    }

    impl<T> Atomic<T> {
        /// Create a new, null atomic pointer.
        #[cfg(feature = "nightly")]
        pub const fn null() -> Atomic<T> {
            Atomic {
                ptr: atomic::AtomicPtr::new(0 as *mut _),
                _marker: PhantomData
            }
        }

        #[cfg(not(feature = "nightly"))]
        pub fn null() -> Atomic<T> {
            Atomic {
                ptr: atomic::AtomicPtr::new(0 as *mut _),
                _marker: PhantomData
            }
        }

        /// Create a new atomic pointer
        pub fn new(data: T) -> Atomic<T> {
            Atomic {
                ptr: atomic::AtomicPtr::new(Box::into_raw(Box::new(data))),
                _marker: PhantomData
            }
        }

        /// Do an atomic load with the given memory ordering.
        ///
        /// In order to perform the load, we must pass in a borrow of a
        /// `Guard`. This is a way of guaranteeing that the thread has pinned the
        /// epoch for the entire lifetime `'a`. In return, you get an optional
        /// `Shared` pointer back (`None` if the `Atomic` is currently null), with
        /// lifetime tied to the guard.
        ///
        /// # Panics
        ///
        /// Panics if `ord` is `Release` or `AcqRel`.
        pub fn load<'a>(&self, ord: Ordering, _: &'a Guard) -> Option<Shared<'a, T>> {
            unsafe { Shared::from_raw(self.ptr.load(ord)) }
        }

        /// Do an atomic store with the given memory ordering.
        ///
        /// Transfers ownership of the given `Owned` pointer, if any. Since no
        /// lifetime information is acquired, no `Guard` value is needed.
        ///
        /// # Panics
        ///
        /// Panics if `ord` is `Acquire` or `AcqRel`.
        pub fn store(&self, val: Option<Owned<T>>, ord: Ordering) {
            self.ptr.store(opt_owned_into_raw(val), ord)
        }

        /// Do an atomic store with the given memory ordering, immediately yielding
        /// a shared reference to the pointer that was stored.
        ///
        /// Transfers ownership of the given `Owned` pointer, yielding a `Shared`
        /// reference to it. Since the reference is valid only for the curent epoch,
        /// it's lifetime is tied to a `Guard` value.
        ///
        /// # Panics
        ///
        /// Panics if `ord` is `Acquire` or `AcqRel`.
        pub fn store_and_ref<'a>(&self, val: Owned<T>, ord: Ordering, _: &'a Guard)
                                 -> Shared<'a, T>
        {
            unsafe {
                let shared = Shared::from_owned(val);
                self.store_shared(Some(shared), ord);
                shared
            }
        }

        /// Do an atomic store of a `Shared` pointer with the given memory ordering.
        ///
        /// This operation does not require a guard, because it does not yield any
        /// new information about the lifetime of a pointer.
        ///
        /// # Panics
        ///
        /// Panics if `ord` is `Acquire` or `AcqRel`.
        pub fn store_shared(&self, val: Option<Shared<T>>, ord: Ordering) {
            self.ptr.store(opt_shared_into_raw(val), ord)
        }

        /// Do a compare-and-set from a `Shared` to an `Owned` pointer with the
        /// given memory ordering.
        ///
        /// As with `store`, this operation does not require a guard; it produces no new
        /// lifetime information. The `Result` indicates whether the CAS succeeded; if
        /// not, ownership of the `new` pointer is returned to the caller.
        pub fn cas(&self, old: Option<Shared<T>>, new: Option<Owned<T>>, ord: Ordering)
                   -> Result<(), Option<Owned<T>>>
        {
            if self.ptr.compare_and_swap(opt_shared_into_raw(old),
                                         opt_owned_as_raw(&new),
                                         ord) == opt_shared_into_raw(old)
            {
                mem::forget(new);
                Ok(())
            } else {
                Err(new)
            }
        }

        /// Do a compare-and-set from a `Shared` to an `Owned` pointer with the
        /// given memory ordering, immediatley acquiring a new `Shared` reference to
        /// the previously-owned pointer if successful.
        ///
        /// This operation is analogous to `store_and_ref`.
        pub fn cas_and_ref<'a>(&self, old: Option<Shared<T>>, new: Owned<T>,
                               ord: Ordering, _: &'a Guard)
                               -> Result<Shared<'a, T>, Owned<T>>
        {
            if self.ptr.compare_and_swap(opt_shared_into_raw(old), new.as_raw(), ord)
                == opt_shared_into_raw(old)
            {
                Ok(unsafe { Shared::from_owned(new) })
            } else {
                Err(new)
            }
        }

        /// Do a compare-and-set from a `Shared` to another `Shared` pointer with
        /// the given memory ordering.
        ///
        /// The boolean return value is `true` when the CAS is successful.
        pub fn cas_shared(&self, old: Option<Shared<T>>, new: Option<Shared<T>>, ord: Ordering)
                          -> bool
        {
            self.ptr.compare_and_swap(opt_shared_into_raw(old),
                                      opt_shared_into_raw(new),
                                      ord) == opt_shared_into_raw(old)
        }

        /// Do an atomic swap with an `Owned` pointer with the given memory ordering.
        pub fn swap<'a>(&self, new: Option<Owned<T>>, ord: Ordering, _: &'a Guard)
                        -> Option<Shared<'a, T>> {
            unsafe { Shared::from_raw(self.ptr.swap(opt_owned_into_raw(new), ord)) }
        }

        /// Do an atomic swap with a `Shared` pointer with the given memory ordering.
        pub fn swap_shared<'a>(&self, new: Option<Shared<T>>, ord: Ordering, _: &'a Guard)
                               -> Option<Shared<'a, T>> {
            unsafe { Shared::from_raw(self.ptr.swap(opt_shared_into_raw(new), ord)) }
        }
    }

# Help

## Keyboard Shortcuts

?
  Show this help dialog
S
  Focus the search field
⇤
  Move up in search results
⇥
  Move down in search results
⏎
  Go to active search result

## 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`)