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use crate::traits::{Atomic, AtomicBitAnd, AtomicBitOr, HasAtomicInt};
use crate::AllocError;
use crate::{div_ceil, InnerFlag};
use alloc::boxed::Box;
use bytemuck::Zeroable;
use core::{
ops::{BitAnd, Not, Shl, Shr},
sync::atomic::Ordering,
};
use num_traits::Num;
#[cfg(feature = "alloc_api")]
use {alloc::alloc::Global, core::alloc::*};
/// An atomic bitfield with a static size, stored in a boxed slice.
///
/// This struct provides methods for working with atomic bitfields, allowing
/// concurrent access and manipulation of individual bits. It is particularly
/// useful when you need to store a large number of boolean flags and want to
/// minimize memory usage.
///
/// # Example
///
/// ```
/// use utils_atomics::{AtomicBitBox};
/// use core::sync::atomic::Ordering;
///
/// let bit_box = AtomicBitBox::<u8>::new(10);
/// assert_eq!(bit_box.get(3, Ordering::Relaxed), Some(false));
/// bit_box.set(3, Ordering::Relaxed);
/// assert_eq!(bit_box.get(3, Ordering::Relaxed), Some(true));
/// ```
#[cfg_attr(docsrs, doc(cfg(feature = "alloc")))]
pub struct AtomicBitBox<
T: HasAtomicInt = InnerFlag,
#[cfg(feature = "alloc_api")] A: Allocator = Global,
> {
#[cfg(feature = "alloc_api")]
bits: Box<[T::AtomicInt], A>,
#[cfg(not(feature = "alloc_api"))]
bits: Box<[T::AtomicInt]>,
len: usize,
}
impl<T: HasAtomicInt> AtomicBitBox<T>
where
T: BitFieldAble,
{
/// Allocates a new bitfield. All values are initialized to `false`.
///
/// # Panics
/// This method panics if the memory allocation fails
#[inline]
pub fn new(len: usize) -> Self {
Self::try_new(len).unwrap()
}
/// Allocates a new bitfield. All values are initialized to `false`.
///
/// # Errors
/// This method returns an error if the memory allocation fails
#[inline]
pub fn try_new(len: usize) -> Result<Self, AllocError> {
let count = div_ceil(len, Self::BIT_SIZE);
let bits;
unsafe {
cfg_if::cfg_if! {
if #[cfg(feature = "nightly")] {
let uninit = Box::<[T::AtomicInt]>::new_zeroed_slice(count);
bits = uninit.assume_init()
} else {
let mut tmp = alloc::vec::Vec::with_capacity(count);
core::ptr::write_bytes(tmp.as_mut_ptr(), 0, count);
tmp.set_len(count);
bits = tmp.into_boxed_slice();
}
};
}
Ok(Self { bits, len })
}
}
cfg_if::cfg_if! {
if #[cfg(feature = "alloc_api")] {
impl<T: HasAtomicInt, A: Allocator> AtomicBitBox<T, A> where T: BitFieldAble {
const BIT_SIZE: usize = 8 * core::mem::size_of::<T>();
/// Allocates a new bitfield. All values are initialized to `false`.
///
/// # Panics
/// This method panics if the memory allocation fails
#[inline]
pub fn new_in (len: usize, alloc: A) -> Self {
Self::try_new_in(len, alloc).unwrap()
}
/// Allocates a new bitfield. All values are initialized to `false`.
///
/// # Errors
/// This method returns an error if the memory allocation fails
#[inline]
pub fn try_new_in (len: usize, alloc: A) -> Result<Self, AllocError> {
let bytes = len.div_ceil(Self::BIT_SIZE);
let bits = unsafe {
let uninit = Box::<[T::AtomicInt], _>::new_zeroed_slice_in(bytes, alloc);
uninit.assume_init()
};
Ok(Self { bits, len })
}
/// Returns the value of the bit at the specified index, or `None` if the index is out of bounds.
///
/// `order` defines the memory ordering for this operation.
pub fn get(&self, idx: usize, order: Ordering) -> Option<bool> {
let byte = idx / Self::BIT_SIZE;
let idx = idx % Self::BIT_SIZE;
if !self.check_bounds(byte, idx) {
return None
}
let byte = unsafe { <[T::AtomicInt]>::get_unchecked(&self.bits, byte) };
let v = byte.load(order);
let mask = T::one() << idx;
return Some((v & mask) != T::zero())
}
/// Sets the value of the bit at the specified index and returns the previous value, or `None` if the index is out of bounds.
///
/// `order` defines the memory ordering for this operation.
#[inline]
pub fn set_value (&self, v: bool, idx: usize, order: Ordering) -> Option<bool> {
if v { return self.set(idx, order) }
self.clear(idx, order)
}
/// Sets the bit at the specified index to `true` and returns the previous value, or `None` if the index is out of bounds.
///
/// `order` defines the memory ordering for this operation.
#[inline]
pub fn set (&self, idx: usize, order: Ordering) -> Option<bool> {
let byte = idx / Self::BIT_SIZE;
let idx = idx % Self::BIT_SIZE;
if !self.check_bounds(byte, idx) {
return None
}
let byte = unsafe { <[T::AtomicInt]>::get_unchecked(&self.bits, byte) };
let mask = T::one() << idx;
let prev = byte.fetch_or(mask, order);
return Some((prev & mask) != T::zero())
}
/// Sets the bit at the specified index to `false` and returns the previous value, or `None` if the index is out of bounds.
///
/// `order` defines the memory ordering for this operation.
#[inline]
pub fn clear (&self, idx: usize, order: Ordering) -> Option<bool> {
let byte = idx / Self::BIT_SIZE;
let idx = idx % Self::BIT_SIZE;
if !self.check_bounds(byte, idx) {
return None
}
let byte = unsafe { <[T::AtomicInt]>::get_unchecked(&self.bits, byte) };
let mask = T::one() << idx;
let prev = byte.fetch_and(!mask, order);
return Some((prev & mask) != T::zero())
}
#[inline]
fn check_bounds (&self, major: usize, minor: usize) -> bool {
if major < self.bits.len() - 1 {
return minor < Self::BIT_SIZE
}
return minor < self.len % Self::BIT_SIZE
}
}
} else {
impl<T: HasAtomicInt> AtomicBitBox<T> where T: BitFieldAble {
const BIT_SIZE: usize = 8 * core::mem::size_of::<T>();
/// Returns the value of the bit at the specified index, or `None` if the index is out of bounds.
///
/// `order` defines the memory ordering for this operation.
pub fn get(&self, idx: usize, order: Ordering) -> Option<bool> {
let byte = idx / Self::BIT_SIZE;
let idx = idx % Self::BIT_SIZE;
if !self.check_bounds(byte, idx) {
return None
}
let byte = unsafe { <[T::AtomicInt]>::get_unchecked(&self.bits, byte) };
let v = byte.load(order);
let mask = T::one() << idx;
return Some((v & mask) != T::zero())
}
/// Sets the value of the bit at the specified index and returns the previous value, or `None` if the index is out of bounds.
///
/// `order` defines the memory ordering for this operation.
#[inline]
pub fn set_value (&self, v: bool, idx: usize, order: Ordering) -> Option<bool> {
if v { return self.set(idx, order) }
self.clear(idx, order)
}
/// Sets the bit at the specified index to `true` and returns the previous value, or `None` if the index is out of bounds.
///
/// `order` defines the memory ordering for this operation.
#[inline]
pub fn set (&self, idx: usize, order: Ordering) -> Option<bool> {
let byte = idx / Self::BIT_SIZE;
let idx = idx % Self::BIT_SIZE;
if !self.check_bounds(byte, idx) {
return None
}
let byte = unsafe { <[T::AtomicInt]>::get_unchecked(&self.bits, byte) };
let mask = T::one() << idx;
let prev = byte.fetch_or(mask, order);
return Some((prev & mask) != T::zero())
}
/// Sets the bit at the specified index to `false` and returns the previous value, or `None` if the index is out of bounds.
///
/// `order` defines the memory ordering for this operation.
#[inline]
pub fn clear (&self, idx: usize, order: Ordering) -> Option<bool> {
let byte = idx / Self::BIT_SIZE;
let idx = idx % Self::BIT_SIZE;
if !self.check_bounds(byte, idx) {
return None
}
let byte = unsafe { <[T::AtomicInt]>::get_unchecked(&self.bits, byte) };
let mask = T::one() << idx;
let prev = byte.fetch_and(!mask, order);
return Some((prev & mask) != T::zero())
}
#[inline]
fn check_bounds (&self, major: usize, minor: usize) -> bool {
if major < self.bits.len() - 1 {
return minor < Self::BIT_SIZE
}
return minor < self.len % Self::BIT_SIZE
}
}
}
}
pub trait BitFieldAble:
Num
+ Copy
+ Zeroable
+ Eq
+ BitAnd<Output = Self>
+ Shl<usize, Output = Self>
+ Shr<usize, Output = Self>
+ Not<Output = Self>
{
}
impl<T> BitFieldAble for T where
T: Num
+ Copy
+ Zeroable
+ Eq
+ BitAnd<Output = Self>
+ Shl<usize, Output = Self>
+ Shr<usize, Output = Self>
+ Not<Output = Self>
{
}
// Thanks ChatGPT!
#[cfg(test)]
mod tests {
use core::sync::atomic::Ordering;
pub type AtomicBitBox = super::AtomicBitBox<u16>;
#[test]
fn new_bitbox() {
let bitbox = AtomicBitBox::new(10);
for i in 0..10 {
assert_eq!(bitbox.get(i, Ordering::SeqCst), Some(false));
}
}
#[test]
fn set_and_get() {
let bitbox = AtomicBitBox::new(10);
bitbox.set(2, Ordering::SeqCst);
bitbox.set(7, Ordering::SeqCst);
for i in 0..10 {
let expected = (i == 2) || (i == 7);
assert_eq!(bitbox.get(i, Ordering::SeqCst), Some(expected));
}
}
#[test]
fn set_false_and_get() {
let bitbox = AtomicBitBox::new(10);
bitbox.set(2, Ordering::SeqCst);
bitbox.set(7, Ordering::SeqCst);
bitbox.clear(2, Ordering::SeqCst);
for i in 0..10 {
let expected = i == 7;
assert_eq!(bitbox.get(i, Ordering::SeqCst), Some(expected));
}
}
#[test]
fn out_of_bounds() {
let bitbox = AtomicBitBox::new(10);
assert_eq!(bitbox.get(11, Ordering::SeqCst), None);
assert_eq!(bitbox.set(11, Ordering::SeqCst), None);
assert_eq!(bitbox.clear(11, Ordering::SeqCst), None);
}
#[cfg(feature = "alloc_api")]
mod custom_allocator {
use core::sync::atomic::Ordering;
use std::alloc::System;
pub type AtomicBitBox = super::super::AtomicBitBox<u16, System>;
#[test]
fn new_bitbox() {
let bitbox = AtomicBitBox::new_in(10, System);
for i in 0..10 {
assert_eq!(bitbox.get(i, Ordering::SeqCst), Some(false));
}
}
#[test]
fn set_and_get() {
let bitbox = AtomicBitBox::new_in(10, System);
bitbox.set(2, Ordering::SeqCst);
bitbox.set(7, Ordering::SeqCst);
for i in 0..10 {
let expected = (i == 2) || (i == 7);
assert_eq!(bitbox.get(i, Ordering::SeqCst), Some(expected));
}
}
#[test]
fn set_false_and_get() {
let bitbox = AtomicBitBox::new_in(10, System);
bitbox.set(2, Ordering::SeqCst);
bitbox.set(7, Ordering::SeqCst);
bitbox.clear(2, Ordering::SeqCst);
for i in 0..10 {
let expected = i == 7;
assert_eq!(bitbox.get(i, Ordering::SeqCst), Some(expected));
}
}
#[test]
fn out_of_bounds() {
let bitbox = AtomicBitBox::new_in(10, System);
assert_eq!(bitbox.get(11, Ordering::SeqCst), None);
assert_eq!(bitbox.set(11, Ordering::SeqCst), None);
assert_eq!(bitbox.clear(11, Ordering::SeqCst), None);
}
}
}