Struct std::sync::atomic::AtomicBool
1.0.0 · source · #[repr(C, align(1))]pub struct AtomicBool { /* private fields */ }
Expand description
A boolean type which can be safely shared between threads.
This type has the same size, alignment, and bit validity as a bool
.
Note: This type is only available on platforms that support atomic
loads and stores of u8
.
Implementations§
source§impl AtomicBool
impl AtomicBool
1.0.0 (const: 1.24.0) · sourcepub const fn new(v: bool) -> AtomicBool
pub const fn new(v: bool) -> AtomicBool
Creates a new AtomicBool
.
§Examples
1.75.0 (const: unstable) · sourcepub unsafe fn from_ptr<'a>(ptr: *mut bool) -> &'a AtomicBool
pub unsafe fn from_ptr<'a>(ptr: *mut bool) -> &'a AtomicBool
Creates a new AtomicBool
from a pointer.
§Examples
use std::sync::atomic::{self, AtomicBool};
// Get a pointer to an allocated value
let ptr: *mut bool = Box::into_raw(Box::new(false));
assert!(ptr.cast::<AtomicBool>().is_aligned());
{
// Create an atomic view of the allocated value
let atomic = unsafe { AtomicBool::from_ptr(ptr) };
// Use `atomic` for atomic operations, possibly share it with other threads
atomic.store(true, atomic::Ordering::Relaxed);
}
// It's ok to non-atomically access the value behind `ptr`,
// since the reference to the atomic ended its lifetime in the block above
assert_eq!(unsafe { *ptr }, true);
// Deallocate the value
unsafe { drop(Box::from_raw(ptr)) }
§Safety
ptr
must be aligned toalign_of::<AtomicBool>()
(note that this is always true, sincealign_of::<AtomicBool>() == 1
).ptr
must be valid for both reads and writes for the whole lifetime'a
.- You must adhere to the Memory model for atomic accesses. In particular, it is not allowed to mix atomic and non-atomic accesses, or atomic accesses of different sizes, without synchronization.
1.15.0 · sourcepub fn get_mut(&mut self) -> &mut bool
pub fn get_mut(&mut self) -> &mut bool
sourcepub fn from_mut(v: &mut bool) -> &mut AtomicBool
🔬This is a nightly-only experimental API. (atomic_from_mut
#76314)
pub fn from_mut(v: &mut bool) -> &mut AtomicBool
atomic_from_mut
#76314)Gets atomic access to a &mut bool
.
§Examples
sourcepub fn get_mut_slice(this: &mut [AtomicBool]) -> &mut [bool]
🔬This is a nightly-only experimental API. (atomic_from_mut
#76314)
pub fn get_mut_slice(this: &mut [AtomicBool]) -> &mut [bool]
atomic_from_mut
#76314)Gets non-atomic access to a &mut [AtomicBool]
slice.
This is safe because the mutable reference guarantees that no other threads are concurrently accessing the atomic data.
§Examples
#![feature(atomic_from_mut)]
use std::sync::atomic::{AtomicBool, Ordering};
let mut some_bools = [const { AtomicBool::new(false) }; 10];
let view: &mut [bool] = AtomicBool::get_mut_slice(&mut some_bools);
assert_eq!(view, [false; 10]);
view[..5].copy_from_slice(&[true; 5]);
std::thread::scope(|s| {
for t in &some_bools[..5] {
s.spawn(move || assert_eq!(t.load(Ordering::Relaxed), true));
}
for f in &some_bools[5..] {
s.spawn(move || assert_eq!(f.load(Ordering::Relaxed), false));
}
});
sourcepub fn from_mut_slice(v: &mut [bool]) -> &mut [AtomicBool]
🔬This is a nightly-only experimental API. (atomic_from_mut
#76314)
pub fn from_mut_slice(v: &mut [bool]) -> &mut [AtomicBool]
atomic_from_mut
#76314)Gets atomic access to a &mut [bool]
slice.
§Examples
#![feature(atomic_from_mut)]
use std::sync::atomic::{AtomicBool, Ordering};
let mut some_bools = [false; 10];
let a = &*AtomicBool::from_mut_slice(&mut some_bools);
std::thread::scope(|s| {
for i in 0..a.len() {
s.spawn(move || a[i].store(true, Ordering::Relaxed));
}
});
assert_eq!(some_bools, [true; 10]);
1.15.0 (const: 1.79.0) · sourcepub const fn into_inner(self) -> bool
pub const fn into_inner(self) -> bool
Consumes the atomic and returns the contained value.
This is safe because passing self
by value guarantees that no other threads are
concurrently accessing the atomic data.
§Examples
1.0.0 · sourcepub fn load(&self, order: Ordering) -> bool
pub fn load(&self, order: Ordering) -> bool
1.0.0 · sourcepub fn store(&self, val: bool, order: Ordering)
pub fn store(&self, val: bool, order: Ordering)
1.0.0 · sourcepub fn swap(&self, val: bool, order: Ordering) -> bool
pub fn swap(&self, val: bool, order: Ordering) -> bool
Stores a value into the bool, returning the previous value.
swap
takes an Ordering
argument which describes the memory ordering
of this operation. All ordering modes are possible. Note that using
Acquire
makes the store part of this operation Relaxed
, and
using Release
makes the load part Relaxed
.
Note: This method is only available on platforms that support atomic
operations on u8
.
§Examples
1.0.0 · sourcepub fn compare_and_swap(
&self,
current: bool,
new: bool,
order: Ordering,
) -> bool
👎Deprecated since 1.50.0: Use compare_exchange
or compare_exchange_weak
instead
pub fn compare_and_swap( &self, current: bool, new: bool, order: Ordering, ) -> bool
compare_exchange
or compare_exchange_weak
insteadStores a value into the bool
if the current value is the same as the current
value.
The return value is always the previous value. If it is equal to current
, then the value
was updated.
compare_and_swap
also takes an Ordering
argument which describes the memory
ordering of this operation. Notice that even when using AcqRel
, the operation
might fail and hence just perform an Acquire
load, but not have Release
semantics.
Using Acquire
makes the store part of this operation Relaxed
if it
happens, and using Release
makes the load part Relaxed
.
Note: This method is only available on platforms that support atomic
operations on u8
.
§Migrating to compare_exchange
and compare_exchange_weak
compare_and_swap
is equivalent to compare_exchange
with the following mapping for
memory orderings:
Original | Success | Failure |
---|---|---|
Relaxed | Relaxed | Relaxed |
Acquire | Acquire | Acquire |
Release | Release | Relaxed |
AcqRel | AcqRel | Acquire |
SeqCst | SeqCst | SeqCst |
compare_exchange_weak
is allowed to fail spuriously even when the comparison succeeds,
which allows the compiler to generate better assembly code when the compare and swap
is used in a loop.
§Examples
use std::sync::atomic::{AtomicBool, Ordering};
let some_bool = AtomicBool::new(true);
assert_eq!(some_bool.compare_and_swap(true, false, Ordering::Relaxed), true);
assert_eq!(some_bool.load(Ordering::Relaxed), false);
assert_eq!(some_bool.compare_and_swap(true, true, Ordering::Relaxed), false);
assert_eq!(some_bool.load(Ordering::Relaxed), false);
1.10.0 · sourcepub fn compare_exchange(
&self,
current: bool,
new: bool,
success: Ordering,
failure: Ordering,
) -> Result<bool, bool>
pub fn compare_exchange( &self, current: bool, new: bool, success: Ordering, failure: Ordering, ) -> Result<bool, bool>
Stores a value into the bool
if the current value is the same as the current
value.
The return value is a result indicating whether the new value was written and containing
the previous value. On success this value is guaranteed to be equal to current
.
compare_exchange
takes two Ordering
arguments to describe the memory
ordering of this operation. success
describes the required ordering for the
read-modify-write operation that takes place if the comparison with current
succeeds.
failure
describes the required ordering for the load operation that takes place when
the comparison fails. Using Acquire
as success ordering makes the store part
of this operation Relaxed
, and using Release
makes the successful load
Relaxed
. The failure ordering can only be SeqCst
, Acquire
or Relaxed
.
Note: This method is only available on platforms that support atomic
operations on u8
.
§Examples
use std::sync::atomic::{AtomicBool, Ordering};
let some_bool = AtomicBool::new(true);
assert_eq!(some_bool.compare_exchange(true,
false,
Ordering::Acquire,
Ordering::Relaxed),
Ok(true));
assert_eq!(some_bool.load(Ordering::Relaxed), false);
assert_eq!(some_bool.compare_exchange(true, true,
Ordering::SeqCst,
Ordering::Acquire),
Err(false));
assert_eq!(some_bool.load(Ordering::Relaxed), false);
1.10.0 · sourcepub fn compare_exchange_weak(
&self,
current: bool,
new: bool,
success: Ordering,
failure: Ordering,
) -> Result<bool, bool>
pub fn compare_exchange_weak( &self, current: bool, new: bool, success: Ordering, failure: Ordering, ) -> Result<bool, bool>
Stores a value into the bool
if the current value is the same as the current
value.
Unlike AtomicBool::compare_exchange
, this function is allowed to spuriously fail even when the
comparison succeeds, which can result in more efficient code on some platforms. The
return value is a result indicating whether the new value was written and containing the
previous value.
compare_exchange_weak
takes two Ordering
arguments to describe the memory
ordering of this operation. success
describes the required ordering for the
read-modify-write operation that takes place if the comparison with current
succeeds.
failure
describes the required ordering for the load operation that takes place when
the comparison fails. Using Acquire
as success ordering makes the store part
of this operation Relaxed
, and using Release
makes the successful load
Relaxed
. The failure ordering can only be SeqCst
, Acquire
or Relaxed
.
Note: This method is only available on platforms that support atomic
operations on u8
.
§Examples
1.0.0 · sourcepub fn fetch_and(&self, val: bool, order: Ordering) -> bool
pub fn fetch_and(&self, val: bool, order: Ordering) -> bool
Logical “and” with a boolean value.
Performs a logical “and” operation on the current value and the argument val
, and sets
the new value to the result.
Returns the previous value.
fetch_and
takes an Ordering
argument which describes the memory ordering
of this operation. All ordering modes are possible. Note that using
Acquire
makes the store part of this operation Relaxed
, and
using Release
makes the load part Relaxed
.
Note: This method is only available on platforms that support atomic
operations on u8
.
§Examples
use std::sync::atomic::{AtomicBool, Ordering};
let foo = AtomicBool::new(true);
assert_eq!(foo.fetch_and(false, Ordering::SeqCst), true);
assert_eq!(foo.load(Ordering::SeqCst), false);
let foo = AtomicBool::new(true);
assert_eq!(foo.fetch_and(true, Ordering::SeqCst), true);
assert_eq!(foo.load(Ordering::SeqCst), true);
let foo = AtomicBool::new(false);
assert_eq!(foo.fetch_and(false, Ordering::SeqCst), false);
assert_eq!(foo.load(Ordering::SeqCst), false);
1.0.0 · sourcepub fn fetch_nand(&self, val: bool, order: Ordering) -> bool
pub fn fetch_nand(&self, val: bool, order: Ordering) -> bool
Logical “nand” with a boolean value.
Performs a logical “nand” operation on the current value and the argument val
, and sets
the new value to the result.
Returns the previous value.
fetch_nand
takes an Ordering
argument which describes the memory ordering
of this operation. All ordering modes are possible. Note that using
Acquire
makes the store part of this operation Relaxed
, and
using Release
makes the load part Relaxed
.
Note: This method is only available on platforms that support atomic
operations on u8
.
§Examples
use std::sync::atomic::{AtomicBool, Ordering};
let foo = AtomicBool::new(true);
assert_eq!(foo.fetch_nand(false, Ordering::SeqCst), true);
assert_eq!(foo.load(Ordering::SeqCst), true);
let foo = AtomicBool::new(true);
assert_eq!(foo.fetch_nand(true, Ordering::SeqCst), true);
assert_eq!(foo.load(Ordering::SeqCst) as usize, 0);
assert_eq!(foo.load(Ordering::SeqCst), false);
let foo = AtomicBool::new(false);
assert_eq!(foo.fetch_nand(false, Ordering::SeqCst), false);
assert_eq!(foo.load(Ordering::SeqCst), true);
1.0.0 · sourcepub fn fetch_or(&self, val: bool, order: Ordering) -> bool
pub fn fetch_or(&self, val: bool, order: Ordering) -> bool
Logical “or” with a boolean value.
Performs a logical “or” operation on the current value and the argument val
, and sets the
new value to the result.
Returns the previous value.
fetch_or
takes an Ordering
argument which describes the memory ordering
of this operation. All ordering modes are possible. Note that using
Acquire
makes the store part of this operation Relaxed
, and
using Release
makes the load part Relaxed
.
Note: This method is only available on platforms that support atomic
operations on u8
.
§Examples
use std::sync::atomic::{AtomicBool, Ordering};
let foo = AtomicBool::new(true);
assert_eq!(foo.fetch_or(false, Ordering::SeqCst), true);
assert_eq!(foo.load(Ordering::SeqCst), true);
let foo = AtomicBool::new(true);
assert_eq!(foo.fetch_or(true, Ordering::SeqCst), true);
assert_eq!(foo.load(Ordering::SeqCst), true);
let foo = AtomicBool::new(false);
assert_eq!(foo.fetch_or(false, Ordering::SeqCst), false);
assert_eq!(foo.load(Ordering::SeqCst), false);
1.0.0 · sourcepub fn fetch_xor(&self, val: bool, order: Ordering) -> bool
pub fn fetch_xor(&self, val: bool, order: Ordering) -> bool
Logical “xor” with a boolean value.
Performs a logical “xor” operation on the current value and the argument val
, and sets
the new value to the result.
Returns the previous value.
fetch_xor
takes an Ordering
argument which describes the memory ordering
of this operation. All ordering modes are possible. Note that using
Acquire
makes the store part of this operation Relaxed
, and
using Release
makes the load part Relaxed
.
Note: This method is only available on platforms that support atomic
operations on u8
.
§Examples
use std::sync::atomic::{AtomicBool, Ordering};
let foo = AtomicBool::new(true);
assert_eq!(foo.fetch_xor(false, Ordering::SeqCst), true);
assert_eq!(foo.load(Ordering::SeqCst), true);
let foo = AtomicBool::new(true);
assert_eq!(foo.fetch_xor(true, Ordering::SeqCst), true);
assert_eq!(foo.load(Ordering::SeqCst), false);
let foo = AtomicBool::new(false);
assert_eq!(foo.fetch_xor(false, Ordering::SeqCst), false);
assert_eq!(foo.load(Ordering::SeqCst), false);
1.81.0 · sourcepub fn fetch_not(&self, order: Ordering) -> bool
pub fn fetch_not(&self, order: Ordering) -> bool
Logical “not” with a boolean value.
Performs a logical “not” operation on the current value, and sets the new value to the result.
Returns the previous value.
fetch_not
takes an Ordering
argument which describes the memory ordering
of this operation. All ordering modes are possible. Note that using
Acquire
makes the store part of this operation Relaxed
, and
using Release
makes the load part Relaxed
.
Note: This method is only available on platforms that support atomic
operations on u8
.
§Examples
use std::sync::atomic::{AtomicBool, Ordering};
let foo = AtomicBool::new(true);
assert_eq!(foo.fetch_not(Ordering::SeqCst), true);
assert_eq!(foo.load(Ordering::SeqCst), false);
let foo = AtomicBool::new(false);
assert_eq!(foo.fetch_not(Ordering::SeqCst), false);
assert_eq!(foo.load(Ordering::SeqCst), true);
1.70.0 (const: 1.70.0) · sourcepub const fn as_ptr(&self) -> *mut bool
pub const fn as_ptr(&self) -> *mut bool
Returns a mutable pointer to the underlying bool
.
Doing non-atomic reads and writes on the resulting boolean can be a data race.
This method is mostly useful for FFI, where the function signature may use
*mut bool
instead of &AtomicBool
.
Returning an *mut
pointer from a shared reference to this atomic is safe because the
atomic types work with interior mutability. All modifications of an atomic change the value
through a shared reference, and can do so safely as long as they use atomic operations. Any
use of the returned raw pointer requires an unsafe
block and still has to uphold the same
restriction: operations on it must be atomic.
§Examples
use std::sync::atomic::AtomicBool;
extern "C" {
fn my_atomic_op(arg: *mut bool);
}
let mut atomic = AtomicBool::new(true);
unsafe {
my_atomic_op(atomic.as_ptr());
}
1.53.0 · sourcepub fn fetch_update<F>(
&self,
set_order: Ordering,
fetch_order: Ordering,
f: F,
) -> Result<bool, bool>
pub fn fetch_update<F>( &self, set_order: Ordering, fetch_order: Ordering, f: F, ) -> Result<bool, bool>
Fetches the value, and applies a function to it that returns an optional
new value. Returns a Result
of Ok(previous_value)
if the function
returned Some(_)
, else Err(previous_value)
.
Note: This may call the function multiple times if the value has been
changed from other threads in the meantime, as long as the function
returns Some(_)
, but the function will have been applied only once to
the stored value.
fetch_update
takes two Ordering
arguments to describe the memory
ordering of this operation. The first describes the required ordering for
when the operation finally succeeds while the second describes the
required ordering for loads. These correspond to the success and failure
orderings of AtomicBool::compare_exchange
respectively.
Using Acquire
as success ordering makes the store part of this
operation Relaxed
, and using Release
makes the final successful
load Relaxed
. The (failed) load ordering can only be SeqCst
,
Acquire
or Relaxed
.
Note: This method is only available on platforms that support atomic
operations on u8
.
§Considerations
This method is not magic; it is not provided by the hardware.
It is implemented in terms of AtomicBool::compare_exchange_weak
, and suffers from the same drawbacks.
In particular, this method will not circumvent the ABA Problem.
§Examples
use std::sync::atomic::{AtomicBool, Ordering};
let x = AtomicBool::new(false);
assert_eq!(x.fetch_update(Ordering::SeqCst, Ordering::SeqCst, |_| None), Err(false));
assert_eq!(x.fetch_update(Ordering::SeqCst, Ordering::SeqCst, |x| Some(!x)), Ok(false));
assert_eq!(x.fetch_update(Ordering::SeqCst, Ordering::SeqCst, |x| Some(!x)), Ok(true));
assert_eq!(x.load(Ordering::SeqCst), false);
Trait Implementations§
1.3.0 · source§impl Debug for AtomicBool
impl Debug for AtomicBool
1.0.0 · source§impl Default for AtomicBool
impl Default for AtomicBool
source§fn default() -> AtomicBool
fn default() -> AtomicBool
Creates an AtomicBool
initialized to false
.