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 in-memory representation 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
const: 1.24.0 · sourcepub const fn new(v: bool) -> AtomicBool
pub const fn new(v: bool) -> AtomicBool
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
#![feature(pointer_is_aligned)]
use std::sync::atomic::{self, AtomicBool};
use std::mem::align_of;
// Get a pointer to an allocated value
let ptr: *mut bool = Box::into_raw(Box::new(false));
assert!(ptr.is_aligned_to(align_of::<AtomicBool>()));
{
// 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)) }
Run§Safety
ptr
must be aligned toalign_of::<AtomicBool>()
(note that on some platforms this can be bigger thanalign_of::<bool>()
).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
Returns a mutable reference to the underlying bool
.
This is safe because the mutable reference guarantees that no other threads are concurrently accessing the atomic data.
§Examples
use std::sync::atomic::{AtomicBool, Ordering};
let mut some_bool = AtomicBool::new(true);
assert_eq!(*some_bool.get_mut(), true);
*some_bool.get_mut() = false;
assert_eq!(some_bool.load(Ordering::SeqCst), false);
Runsourcepub 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)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)Get 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, inline_const)]
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));
}
});
Runsourcepub 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)Get 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]);
Run1.15.0 (const: unstable) · sourcepub fn into_inner(self) -> bool
pub 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
use std::sync::atomic::AtomicBool;
let some_bool = AtomicBool::new(true);
assert_eq!(some_bool.into_inner(), true);
Runsourcepub fn load(&self, order: Ordering) -> bool
pub fn load(&self, order: Ordering) -> bool
Loads a value from the bool.
load
takes an Ordering
argument which describes the memory ordering
of this operation. Possible values are SeqCst
, Acquire
and Relaxed
.
§Panics
Panics if order
is Release
or AcqRel
.
§Examples
use std::sync::atomic::{AtomicBool, Ordering};
let some_bool = AtomicBool::new(true);
assert_eq!(some_bool.load(Ordering::Relaxed), true);
Runsourcepub fn store(&self, val: bool, order: Ordering)
pub fn store(&self, val: bool, order: Ordering)
Stores a value into the bool.
store
takes an Ordering
argument which describes the memory ordering
of this operation. Possible values are SeqCst
, Release
and Relaxed
.
§Panics
Panics if order
is Acquire
or AcqRel
.
§Examples
use std::sync::atomic::{AtomicBool, Ordering};
let some_bool = AtomicBool::new(true);
some_bool.store(false, Ordering::Relaxed);
assert_eq!(some_bool.load(Ordering::Relaxed), false);
Runsourcepub 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
use std::sync::atomic::{AtomicBool, Ordering};
let some_bool = AtomicBool::new(true);
assert_eq!(some_bool.swap(false, Ordering::Relaxed), true);
assert_eq!(some_bool.load(Ordering::Relaxed), false);
Runsourcepub 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);
Run1.10.0 · 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);
Run1.10.0 · 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
use std::sync::atomic::{AtomicBool, Ordering};
let val = AtomicBool::new(false);
let new = true;
let mut old = val.load(Ordering::Relaxed);
loop {
match val.compare_exchange_weak(old, new, Ordering::SeqCst, Ordering::Relaxed) {
Ok(_) => break,
Err(x) => old = x,
}
}
Runsourcepub 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);
Runsourcepub 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);
Runsourcepub 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);
Runsourcepub 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);
Runsourcepub fn fetch_not(&self, order: Ordering) -> bool
🔬This is a nightly-only experimental API. (atomic_bool_fetch_not
#98485)
pub fn fetch_not(&self, order: Ordering) -> bool
atomic_bool_fetch_not
#98485)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
#![feature(atomic_bool_fetch_not)]
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);
Run1.70.0 (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 integer 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
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);
RunTrait Implementations§
1.3.0 · source§impl Debug for AtomicBool
impl Debug for AtomicBool
source§impl Default for AtomicBool
impl Default for AtomicBool
source§fn default() -> AtomicBool
fn default() -> AtomicBool
Creates an AtomicBool
initialized to false
.