Struct AtomicBool

#[repr(C, align(1))]
pub struct AtomicBool { /* private fields */ }

A boolean type which can be safely shared between threads.

This type has the same in-memory representation as a bool.

If the compiler and the platform support atomic loads and stores of u8, this type is a wrapper for the standard library’s AtomicBool. If the platform supports it but the compiler does not, atomic operations are implemented using inline assembly.

Implementations

impl AtomicBool

pub const fn new(v: bool) -> Self

Creates a new AtomicBool.

Examples

use portable_atomic::AtomicBool;

let atomic_true = AtomicBool::new(true);
let atomic_false = AtomicBool::new(false);

pub const unsafe fn from_ptr<'a>(ptr: *mut bool) -> &'a Self

Creates a new AtomicBool from a pointer.

This is const fn on Rust 1.83+.

Safety

• ptr must be aligned to align_of::<AtomicBool>() (note that on some platforms this can be bigger than align_of::<bool>()).
• ptr must be valid for both reads and writes for the whole lifetime 'a.
• If this atomic type is lock-free, non-atomic accesses to the value behind ptr must have a happens-before relationship with atomic accesses via the returned value (or vice-versa).
  • In other words, time periods where the value is accessed atomically may not overlap with periods where the value is accessed non-atomically.
  • This requirement is trivially satisfied if ptr is never used non-atomically for the duration of lifetime 'a. Most use cases should be able to follow this guideline.
  • This requirement is also trivially satisfied if all accesses (atomic or not) are done from the same thread.
• If this atomic type is not lock-free:
  • Any accesses to the value behind ptr must have a happens-before relationship with accesses via the returned value (or vice-versa).
  • Any concurrent accesses to the value behind ptr for the duration of lifetime 'a must be compatible with operations performed by this atomic type.
• This method must not be used to create overlapping or mixed-size atomic accesses, as these are not supported by the memory model.

pub fn is_lock_free() -> bool

Returns true if operations on values of this type are lock-free.

If the compiler or the platform doesn’t support the necessary atomic instructions, global locks for every potentially concurrent atomic operation will be used.

Examples

use portable_atomic::AtomicBool;

let is_lock_free = AtomicBool::is_lock_free();

pub const fn is_always_lock_free() -> bool

Returns true if operations on values of this type are lock-free.

If the compiler or the platform doesn’t support the necessary atomic instructions, global locks for every potentially concurrent atomic operation will be used.

Note: If the atomic operation relies on dynamic CPU feature detection, this type may be lock-free even if the function returns false.

Examples

use portable_atomic::AtomicBool;

const IS_ALWAYS_LOCK_FREE: bool = AtomicBool::is_always_lock_free();

pub const 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.

This is const fn on Rust 1.83+.

Examples

use portable_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);

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.

This is const fn on Rust 1.56+.

Examples

use portable_atomic::AtomicBool;

let some_bool = AtomicBool::new(true);
assert_eq!(some_bool.into_inner(), true);

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 portable_atomic::{AtomicBool, Ordering};

let some_bool = AtomicBool::new(true);

assert_eq!(some_bool.load(Ordering::Relaxed), true);

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 portable_atomic::{AtomicBool, Ordering};

let some_bool = AtomicBool::new(true);

some_bool.store(false, Ordering::Relaxed);
assert_eq!(some_bool.load(Ordering::Relaxed), false);

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.

Examples

use portable_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);

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.

Panics

Panics if failure is Release, AcqRel.

Examples

use portable_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);

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.

Panics

Panics if failure is Release, AcqRel.

Examples

use portable_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,
    }
}

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.

Examples

use portable_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);

pub fn and(&self, val: bool, order: Ordering)

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.

Unlike fetch_and, this does not return the previous value.

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.

This function may generate more efficient code than fetch_and on some platforms.

• x86/x86_64: lock and instead of cmpxchg loop
• MSP430: and instead of disabling interrupts

Note: On x86/x86_64, the use of either function should not usually affect the generated code, because LLVM can properly optimize the case where the result is unused.

Examples

use portable_atomic::{AtomicBool, Ordering};

let foo = AtomicBool::new(true);
foo.and(false, Ordering::SeqCst);
assert_eq!(foo.load(Ordering::SeqCst), false);

let foo = AtomicBool::new(true);
foo.and(true, Ordering::SeqCst);
assert_eq!(foo.load(Ordering::SeqCst), true);

let foo = AtomicBool::new(false);
foo.and(false, Ordering::SeqCst);
assert_eq!(foo.load(Ordering::SeqCst), false);

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.

Examples

use portable_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);

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.

Examples

use portable_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);

pub fn or(&self, val: bool, order: Ordering)

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.

Unlike fetch_or, this does not return the previous value.

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.

This function may generate more efficient code than fetch_or on some platforms.

• x86/x86_64: lock or instead of cmpxchg loop
• MSP430: bis instead of disabling interrupts

Note: On x86/x86_64, the use of either function should not usually affect the generated code, because LLVM can properly optimize the case where the result is unused.

Examples

use portable_atomic::{AtomicBool, Ordering};

let foo = AtomicBool::new(true);
foo.or(false, Ordering::SeqCst);
assert_eq!(foo.load(Ordering::SeqCst), true);

let foo = AtomicBool::new(true);
foo.or(true, Ordering::SeqCst);
assert_eq!(foo.load(Ordering::SeqCst), true);

let foo = AtomicBool::new(false);
foo.or(false, Ordering::SeqCst);
assert_eq!(foo.load(Ordering::SeqCst), false);

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.

Examples

use portable_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);

pub fn xor(&self, val: bool, order: Ordering)

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.

Unlike fetch_xor, this does not return the previous value.

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.

This function may generate more efficient code than fetch_xor on some platforms.

• x86/x86_64: lock xor instead of cmpxchg loop
• MSP430: xor instead of disabling interrupts

Note: On x86/x86_64, the use of either function should not usually affect the generated code, because LLVM can properly optimize the case where the result is unused.

Examples

use portable_atomic::{AtomicBool, Ordering};

let foo = AtomicBool::new(true);
foo.xor(false, Ordering::SeqCst);
assert_eq!(foo.load(Ordering::SeqCst), true);

let foo = AtomicBool::new(true);
foo.xor(true, Ordering::SeqCst);
assert_eq!(foo.load(Ordering::SeqCst), false);

let foo = AtomicBool::new(false);
foo.xor(false, Ordering::SeqCst);
assert_eq!(foo.load(Ordering::SeqCst), false);

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.

Examples

use portable_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);

pub fn not(&self, order: Ordering)

Logical “not” with a boolean value.

Performs a logical “not” operation on the current value, and sets the new value to the result.

Unlike fetch_not, this does not return the previous value.

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.

This function may generate more efficient code than fetch_not on some platforms.

• x86/x86_64: lock xor instead of cmpxchg loop
• MSP430: xor instead of disabling interrupts

Note: On x86/x86_64, the use of either function should not usually affect the generated code, because LLVM can properly optimize the case where the result is unused.

Examples

use portable_atomic::{AtomicBool, Ordering};

let foo = AtomicBool::new(true);
foo.not(Ordering::SeqCst);
assert_eq!(foo.load(Ordering::SeqCst), false);

let foo = AtomicBool::new(false);
foo.not(Ordering::SeqCst);
assert_eq!(foo.load(Ordering::SeqCst), true);

pub fn fetch_update<F>( &self, set_order: Ordering, fetch_order: Ordering, f: F, ) -> Result<bool, bool>

where F: FnMut(bool) -> Option<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 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.

Considerations

This method is not magic; it is not provided by the hardware. It is implemented in terms of compare_exchange_weak, and suffers from the same drawbacks. In particular, this method will not circumvent the ABA Problem.

Panics

Panics if fetch_order is Release, AcqRel.

Examples

use portable_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);

pub const fn as_ptr(&self) -> *mut bool

Returns a mutable pointer to the underlying bool.

Returning an *mut pointer from a shared reference to this atomic is safe because the atomic types work with interior mutability. Any use of the returned raw pointer requires an unsafe block and has to uphold the safety requirements. If there is concurrent access, note the following additional safety requirements:

• If this atomic type is lock-free, any concurrent operations on it must be atomic.
• Otherwise, any concurrent operations on it must be compatible with operations performed by this atomic type.

This is const fn on Rust 1.58+.

Trait Implementations

impl Debug for AtomicBool

fn fmt(&self, f: &mut Formatter<'_>) -> Result

Formats the value using the given formatter.

impl Default for AtomicBool

fn default() -> Self

Creates an AtomicBool initialized to false.

impl From<bool> for AtomicBool

fn from(b: bool) -> Self

Converts a bool into an AtomicBool.

impl RefUnwindSafe for AtomicBool

impl Sync for AtomicBool