chore: add vendor directory

1 files changed, 1711 insertions, 0 deletions

diff --git a/vendor/fixedbitset/src/lib.rs b/vendor/fixedbitset/src/lib.rs
new file mode 100644
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+++ b/vendor/fixedbitset/src/lib.rs
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+//! `FixedBitSet` is a simple fixed size set of bits.
+//!
+//! ### Crate features
+//!
+//! - `std` (default feature)  
+//!   Disabling this feature disables using std and instead uses crate alloc.
+//!
+//! ### SIMD Acceleration
+//! `fixedbitset` is written with SIMD in mind. The backing store and set operations will use aligned SIMD data types and instructions when compiling
+//! for compatible target platforms. The use of SIMD generally enables better performance in many set and batch operations (i.e. intersection/union/inserting a range).
+//!
+//!  When SIMD is not available on the target, the crate will gracefully fallback to a default implementation.  It is intended to add support for other SIMD architectures
+//! once they appear in stable Rust.
+//!
+//! Currently only SSE2/AVX/AVX2 on x86/x86_64 and wasm32 SIMD are supported as this is what stable Rust supports.
+#![no_std]
+#![deny(clippy::undocumented_unsafe_blocks)]
+
+extern crate alloc;
+use alloc::{vec, vec::Vec};
+
+mod block;
+mod range;
+
+#[cfg(feature = "serde")]
+extern crate serde;
+#[cfg(feature = "serde")]
+mod serde_impl;
+
+use core::fmt::Write;
+use core::fmt::{Binary, Display, Error, Formatter};
+
+use core::cmp::Ordering;
+use core::hash::Hash;
+use core::iter::{Chain, FusedIterator};
+use core::mem::ManuallyDrop;
+use core::mem::MaybeUninit;
+use core::ops::{BitAnd, BitAndAssign, BitOr, BitOrAssign, BitXor, BitXorAssign, Index};
+use core::ptr::NonNull;
+pub use range::IndexRange;
+
+pub(crate) const BITS: usize = core::mem::size_of::<Block>() * 8;
+#[cfg(feature = "serde")]
+pub(crate) const BYTES: usize = core::mem::size_of::<Block>();
+
+use block::Block as SimdBlock;
+pub type Block = usize;
+
+#[inline]
+fn div_rem(x: usize, denominator: usize) -> (usize, usize) {
+    (x / denominator, x % denominator)
+}
+
+fn vec_into_parts<T>(vec: Vec<T>) -> (NonNull<T>, usize, usize) {
+    let mut vec = ManuallyDrop::new(vec);
+    (
+        // SAFETY: A Vec's internal pointer is always non-null.
+        unsafe { NonNull::new_unchecked(vec.as_mut_ptr()) },
+        vec.capacity(),
+        vec.len(),
+    )
+}
+
+/// `FixedBitSet` is a simple fixed size set of bits that each can
+/// be enabled (1 / **true**) or disabled (0 / **false**).
+///
+/// The bit set has a fixed capacity in terms of enabling bits (and the
+/// capacity can grow using the `grow` method).
+///
+/// Derived traits depend on both the zeros and ones, so [0,1] is not equal to
+/// [0,1,0].
+#[derive(Debug, Eq)]
+pub struct FixedBitSet {
+    pub(crate) data: NonNull<MaybeUninit<SimdBlock>>,
+    capacity: usize,
+    /// length in bits
+    pub(crate) length: usize,
+}
+
+// SAFETY: FixedBitset contains no thread-local state and can be safely sent between threads
+unsafe impl Send for FixedBitSet {}
+// SAFETY: FixedBitset does not provide simultaneous unsynchronized mutable access to the
+// underlying buffer.
+unsafe impl Sync for FixedBitSet {}
+
+impl FixedBitSet {
+    /// Create a new empty **FixedBitSet**.
+    pub const fn new() -> Self {
+        FixedBitSet {
+            data: NonNull::dangling(),
+            capacity: 0,
+            length: 0,
+        }
+    }
+
+    /// Create a new **FixedBitSet** with a specific number of bits,
+    /// all initially clear.
+    pub fn with_capacity(bits: usize) -> Self {
+        let (mut blocks, rem) = div_rem(bits, SimdBlock::BITS);
+        blocks += (rem > 0) as usize;
+        Self::from_blocks_and_len(vec![SimdBlock::NONE; blocks], bits)
+    }
+
+    #[inline]
+    fn from_blocks_and_len(data: Vec<SimdBlock>, length: usize) -> Self {
+        let (data, capacity, _) = vec_into_parts(data);
+        FixedBitSet {
+            data: data.cast(),
+            capacity,
+            length,
+        }
+    }
+
+    /// Create a new **FixedBitSet** with a specific number of bits,
+    /// initialized from provided blocks.
+    ///
+    /// If the blocks are not the exact size needed for the capacity
+    /// they will be padded with zeros (if shorter) or truncated to
+    /// the capacity (if longer).
+    ///
+    /// For example:
+    /// ```
+    /// let data = vec![4];
+    /// let bs = fixedbitset::FixedBitSet::with_capacity_and_blocks(4, data);
+    /// assert_eq!(format!("{:b}", bs), "0010");
+    /// ```
+    pub fn with_capacity_and_blocks<I: IntoIterator<Item = Block>>(bits: usize, blocks: I) -> Self {
+        let mut bitset = Self::with_capacity(bits);
+        for (subblock, value) in bitset.as_mut_slice().iter_mut().zip(blocks.into_iter()) {
+            *subblock = value;
+        }
+        bitset
+    }
+
+    /// Grow capacity to **bits**, all new bits initialized to zero
+    #[inline]
+    pub fn grow(&mut self, bits: usize) {
+        #[cold]
+        #[track_caller]
+        #[inline(never)]
+        fn do_grow(slf: &mut FixedBitSet, bits: usize) {
+            // SAFETY: The provided fill is initialized to NONE.
+            unsafe { slf.grow_inner(bits, MaybeUninit::new(SimdBlock::NONE)) };
+        }
+
+        if bits > self.length {
+            do_grow(self, bits);
+        }
+    }
+
+    /// # Safety
+    /// If `fill` is uninitialized, the memory must not be accessed and must be immediately
+    /// written over
+    #[inline(always)]
+    unsafe fn grow_inner(&mut self, bits: usize, fill: MaybeUninit<SimdBlock>) {
+        // SAFETY: The data pointer and capacity were created from a Vec initially. The block
+        // len is identical to that of the original.
+        let mut data = unsafe {
+            Vec::from_raw_parts(self.data.as_ptr(), self.simd_block_len(), self.capacity)
+        };
+        let (mut blocks, rem) = div_rem(bits, SimdBlock::BITS);
+        blocks += (rem > 0) as usize;
+        data.resize(blocks, fill);
+        let (data, capacity, _) = vec_into_parts(data);
+        self.data = data;
+        self.capacity = capacity;
+        self.length = bits;
+    }
+
+    #[inline]
+    unsafe fn get_unchecked(&self, subblock: usize) -> &Block {
+        &*self.data.as_ptr().cast::<Block>().add(subblock)
+    }
+
+    #[inline]
+    unsafe fn get_unchecked_mut(&mut self, subblock: usize) -> &mut Block {
+        &mut *self.data.as_ptr().cast::<Block>().add(subblock)
+    }
+
+    #[inline]
+    fn usize_len(&self) -> usize {
+        let (mut blocks, rem) = div_rem(self.length, BITS);
+        blocks += (rem > 0) as usize;
+        blocks
+    }
+
+    #[inline]
+    fn simd_block_len(&self) -> usize {
+        let (mut blocks, rem) = div_rem(self.length, SimdBlock::BITS);
+        blocks += (rem > 0) as usize;
+        blocks
+    }
+
+    #[inline]
+    fn batch_count_ones(blocks: impl IntoIterator<Item = Block>) -> usize {
+        blocks.into_iter().map(|x| x.count_ones() as usize).sum()
+    }
+
+    #[inline]
+    fn as_simd_slice(&self) -> &[SimdBlock] {
+        // SAFETY: The slice constructed is within bounds of the underlying allocation. This function
+        // is called with a read-only borrow so no other write can happen as long as the returned borrow lives.
+        unsafe { core::slice::from_raw_parts(self.data.as_ptr().cast(), self.simd_block_len()) }
+    }
+
+    #[inline]
+    fn as_mut_simd_slice(&mut self) -> &mut [SimdBlock] {
+        // SAFETY: The slice constructed is within bounds of the underlying allocation. This function
+        // is called with a mutable borrow so no other read or write can happen as long as the returned borrow lives.
+        unsafe { core::slice::from_raw_parts_mut(self.data.as_ptr().cast(), self.simd_block_len()) }
+    }
+
+    #[inline]
+    fn as_simd_slice_uninit(&self) -> &[MaybeUninit<SimdBlock>] {
+        // SAFETY: The slice constructed is within bounds of the underlying allocation. This function
+        // is called with a read-only borrow so no other write can happen as long as the returned borrow lives.
+        unsafe { core::slice::from_raw_parts(self.data.as_ptr(), self.simd_block_len()) }
+    }
+
+    #[inline]
+    fn as_mut_simd_slice_uninit(&mut self) -> &mut [MaybeUninit<SimdBlock>] {
+        // SAFETY: The slice constructed is within bounds of the underlying allocation. This function
+        // is called with a mutable borrow so no other read or write can happen as long as the returned borrow lives.
+        unsafe { core::slice::from_raw_parts_mut(self.data.as_ptr(), self.simd_block_len()) }
+    }
+
+    /// Grows the internal size of the bitset before inserting a bit
+    ///
+    /// Unlike `insert`, this cannot panic, but may allocate if the bit is outside of the existing buffer's range.
+    ///
+    /// This is faster than calling `grow` then `insert` in succession.
+    #[inline]
+    pub fn grow_and_insert(&mut self, bits: usize) {
+        self.grow(bits + 1);
+
+        let (blocks, rem) = div_rem(bits, BITS);
+        // SAFETY: The above grow ensures that the block is inside the Vec's allocation.
+        unsafe {
+            *self.get_unchecked_mut(blocks) |= 1 << rem;
+        }
+    }
+
+    /// The length of the [`FixedBitSet`] in bits.
+    ///
+    /// Note: `len` includes both set and unset bits.
+    /// ```
+    /// # use fixedbitset::FixedBitSet;
+    /// let bitset = FixedBitSet::with_capacity(10);
+    /// // there are 0 set bits, but 10 unset bits
+    /// assert_eq!(bitset.len(), 10);
+    /// ```
+    /// `len` does not return the count of set bits. For that, use
+    /// [`bitset.count_ones(..)`](FixedBitSet::count_ones) instead.
+    #[inline]
+    pub fn len(&self) -> usize {
+        self.length
+    }
+
+    /// `true` if the [`FixedBitSet`] is empty.
+    ///
+    /// Note that an "empty" `FixedBitSet` is a `FixedBitSet` with
+    /// no bits (meaning: it's length is zero). If you want to check
+    /// if all bits are unset, use [`FixedBitSet::is_clear`].
+    ///
+    /// ```
+    /// # use fixedbitset::FixedBitSet;
+    /// let bitset = FixedBitSet::with_capacity(10);
+    /// assert!(!bitset.is_empty());
+    ///
+    /// let bitset = FixedBitSet::with_capacity(0);
+    /// assert!(bitset.is_empty());
+    /// ```
+    #[inline]
+    pub fn is_empty(&self) -> bool {
+        self.len() == 0
+    }
+
+    /// `true` if all bits in the [`FixedBitSet`] are unset.
+    ///
+    /// As opposed to [`FixedBitSet::is_empty`], which is `true` only for
+    /// sets without any bits, set or unset.
+    ///
+    /// ```
+    /// # use fixedbitset::FixedBitSet;
+    /// let mut bitset = FixedBitSet::with_capacity(10);
+    /// assert!(bitset.is_clear());
+    ///
+    /// bitset.insert(2);
+    /// assert!(!bitset.is_clear());
+    /// ```
+    ///
+    /// This is equivalent to [`bitset.count_ones(..) == 0`](FixedBitSet::count_ones).
+    #[inline]
+    pub fn is_clear(&self) -> bool {
+        self.as_simd_slice().iter().all(|block| block.is_empty())
+    }
+
+    /// Finds the lowest set bit in the bitset.
+    ///
+    /// Returns `None` if there aren't any set bits.
+    ///
+    /// ```
+    /// # use fixedbitset::FixedBitSet;
+    /// let mut bitset = FixedBitSet::with_capacity(10);
+    /// assert_eq!(bitset.minimum(), None);
+    ///
+    /// bitset.insert(2);
+    /// assert_eq!(bitset.minimum(), Some(2));
+    /// bitset.insert(8);
+    /// assert_eq!(bitset.minimum(), Some(2));
+    /// ```
+    #[inline]
+    pub fn minimum(&self) -> Option<usize> {
+        let (block_idx, block) = self
+            .as_simd_slice()
+            .iter()
+            .enumerate()
+            .find(|&(_, block)| !block.is_empty())?;
+        let mut inner = 0;
+        let mut trailing = 0;
+        for subblock in block.into_usize_array() {
+            if subblock != 0 {
+                trailing = subblock.trailing_zeros() as usize;
+                break;
+            } else {
+                inner += BITS;
+            }
+        }
+        Some(block_idx * SimdBlock::BITS + inner + trailing)
+    }
+
+    /// Finds the highest set bit in the bitset.
+    ///
+    /// Returns `None` if there aren't any set bits.
+    ///
+    /// ```
+    /// # use fixedbitset::FixedBitSet;
+    /// let mut bitset = FixedBitSet::with_capacity(10);
+    /// assert_eq!(bitset.maximum(), None);
+    ///
+    /// bitset.insert(8);
+    /// assert_eq!(bitset.maximum(), Some(8));
+    /// bitset.insert(2);
+    /// assert_eq!(bitset.maximum(), Some(8));
+    /// ```
+    #[inline]
+    pub fn maximum(&self) -> Option<usize> {
+        let (block_idx, block) = self
+            .as_simd_slice()
+            .iter()
+            .rev()
+            .enumerate()
+            .find(|&(_, block)| !block.is_empty())?;
+        let mut inner = 0;
+        let mut leading = 0;
+        for subblock in block.into_usize_array().iter().rev() {
+            if *subblock != 0 {
+                leading = subblock.leading_zeros() as usize;
+                break;
+            } else {
+                inner += BITS;
+            }
+        }
+        let max = self.simd_block_len() * SimdBlock::BITS;
+        Some(max - block_idx * SimdBlock::BITS - inner - leading - 1)
+    }
+
+    /// `true` if all bits in the [`FixedBitSet`] are set.
+    ///
+    /// ```
+    /// # use fixedbitset::FixedBitSet;
+    /// let mut bitset = FixedBitSet::with_capacity(10);
+    /// assert!(!bitset.is_full());
+    ///
+    /// bitset.insert_range(..);
+    /// assert!(bitset.is_full());
+    /// ```
+    ///
+    /// This is equivalent to [`bitset.count_ones(..) == bitset.len()`](FixedBitSet::count_ones).
+    #[inline]
+    pub fn is_full(&self) -> bool {
+        self.contains_all_in_range(..)
+    }
+
+    /// Return **true** if the bit is enabled in the **FixedBitSet**,
+    /// **false** otherwise.
+    ///
+    /// Note: bits outside the capacity are always disabled.
+    ///
+    /// Note: Also available with index syntax: `bitset[bit]`.
+    #[inline]
+    pub fn contains(&self, bit: usize) -> bool {
+        (bit < self.length)
+            // SAFETY: The above check ensures that the block and bit are within bounds.
+            .then(|| unsafe { self.contains_unchecked(bit) })
+            .unwrap_or(false)
+    }
+
+    /// Return **true** if the bit is enabled in the **FixedBitSet**,
+    /// **false** otherwise.
+    ///
+    /// Note: unlike `contains`, calling this with an invalid `bit`
+    /// is undefined behavior.
+    ///
+    /// # Safety
+    /// `bit` must be less than `self.len()`
+    #[inline]
+    pub unsafe fn contains_unchecked(&self, bit: usize) -> bool {
+        let (block, i) = div_rem(bit, BITS);
+        (self.get_unchecked(block) & (1 << i)) != 0
+    }
+
+    /// Clear all bits.
+    #[inline]
+    pub fn clear(&mut self) {
+        for elt in self.as_mut_simd_slice().iter_mut() {
+            *elt = SimdBlock::NONE
+        }
+    }
+
+    /// Enable `bit`.
+    ///
+    /// **Panics** if **bit** is out of bounds.
+    #[inline]
+    pub fn insert(&mut self, bit: usize) {
+        assert!(
+            bit < self.length,
+            "insert at index {} exceeds fixedbitset size {}",
+            bit,
+            self.length
+        );
+        // SAFETY: The above assertion ensures that the block is inside the Vec's allocation.
+        unsafe {
+            self.insert_unchecked(bit);
+        }
+    }
+
+    /// Enable `bit` without any length checks.
+    ///
+    /// # Safety
+    /// `bit` must be less than `self.len()`
+    #[inline]
+    pub unsafe fn insert_unchecked(&mut self, bit: usize) {
+        let (block, i) = div_rem(bit, BITS);
+        // SAFETY: The above assertion ensures that the block is inside the Vec's allocation.
+        unsafe {
+            *self.get_unchecked_mut(block) |= 1 << i;
+        }
+    }
+
+    /// Disable `bit`.
+    ///
+    /// **Panics** if **bit** is out of bounds.
+    #[inline]
+    pub fn remove(&mut self, bit: usize) {
+        assert!(
+            bit < self.length,
+            "remove at index {} exceeds fixedbitset size {}",
+            bit,
+            self.length
+        );
+        // SAFETY: The above assertion ensures that the block is inside the Vec's allocation.
+        unsafe {
+            self.remove_unchecked(bit);
+        }
+    }
+
+    /// Disable `bit` without any bounds checking.
+    ///
+    /// # Safety
+    /// `bit` must be less than `self.len()`
+    #[inline]
+    pub unsafe fn remove_unchecked(&mut self, bit: usize) {
+        let (block, i) = div_rem(bit, BITS);
+        // SAFETY: The above assertion ensures that the block is inside the Vec's allocation.
+        unsafe {
+            *self.get_unchecked_mut(block) &= !(1 << i);
+        }
+    }
+
+    /// Enable `bit`, and return its previous value.
+    ///
+    /// **Panics** if **bit** is out of bounds.
+    #[inline]
+    pub fn put(&mut self, bit: usize) -> bool {
+        assert!(
+            bit < self.length,
+            "put at index {} exceeds fixedbitset size {}",
+            bit,
+            self.length
+        );
+        // SAFETY: The above assertion ensures that the block is inside the Vec's allocation.
+        unsafe { self.put_unchecked(bit) }
+    }
+
+    /// Enable `bit`, and return its previous value without doing any bounds checking.
+    ///
+    /// # Safety
+    /// `bit` must be less than `self.len()`
+    #[inline]
+    pub unsafe fn put_unchecked(&mut self, bit: usize) -> bool {
+        let (block, i) = div_rem(bit, BITS);
+        // SAFETY: The above assertion ensures that the block is inside the Vec's allocation.
+        unsafe {
+            let word = self.get_unchecked_mut(block);
+            let prev = *word & (1 << i) != 0;
+            *word |= 1 << i;
+            prev
+        }
+    }
+
+    /// Toggle `bit` (inverting its state).
+    ///
+    /// ***Panics*** if **bit** is out of bounds
+    #[inline]
+    pub fn toggle(&mut self, bit: usize) {
+        assert!(
+            bit < self.length,
+            "toggle at index {} exceeds fixedbitset size {}",
+            bit,
+            self.length
+        );
+        // SAFETY: The above assertion ensures that the block is inside the Vec's allocation.
+        unsafe {
+            self.toggle_unchecked(bit);
+        }
+    }
+
+    /// Toggle `bit` (inverting its state) without any bounds checking.
+    ///
+    /// # Safety
+    /// `bit` must be less than `self.len()`
+    #[inline]
+    pub unsafe fn toggle_unchecked(&mut self, bit: usize) {
+        let (block, i) = div_rem(bit, BITS);
+        // SAFETY: The above assertion ensures that the block is inside the Vec's allocation.
+        unsafe {
+            *self.get_unchecked_mut(block) ^= 1 << i;
+        }
+    }
+
+    /// Sets a bit to the provided `enabled` value.
+    ///
+    /// **Panics** if **bit** is out of bounds.
+    #[inline]
+    pub fn set(&mut self, bit: usize, enabled: bool) {
+        assert!(
+            bit < self.length,
+            "set at index {} exceeds fixedbitset size {}",
+            bit,
+            self.length
+        );
+        // SAFETY: The above assertion ensures that the block is inside the Vec's allocation.
+        unsafe {
+            self.set_unchecked(bit, enabled);
+        }
+    }
+
+    /// Sets a bit to the provided `enabled` value without doing any bounds checking.
+    ///
+    /// # Safety
+    /// `bit` must be less than `self.len()`
+    #[inline]
+    pub unsafe fn set_unchecked(&mut self, bit: usize, enabled: bool) {
+        let (block, i) = div_rem(bit, BITS);
+        // SAFETY: The above assertion ensures that the block is inside the Vec's allocation.
+        let elt = unsafe { self.get_unchecked_mut(block) };
+        if enabled {
+            *elt |= 1 << i;
+        } else {
+            *elt &= !(1 << i);
+        }
+    }
+
+    /// Copies boolean value from specified bit to the specified bit.
+    ///
+    /// If `from` is out-of-bounds, `to` will be unset.
+    ///
+    /// **Panics** if **to** is out of bounds.
+    #[inline]
+    pub fn copy_bit(&mut self, from: usize, to: usize) {
+        assert!(
+            to < self.length,
+            "copy to index {} exceeds fixedbitset size {}",
+            to,
+            self.length
+        );
+        let enabled = self.contains(from);
+        // SAFETY: The above assertion ensures that the block is inside the Vec's allocation.
+        unsafe { self.set_unchecked(to, enabled) };
+    }
+
+    /// Copies boolean value from specified bit to the specified bit.
+    ///
+    /// Note: unlike `copy_bit`, calling this with an invalid `from`
+    /// is undefined behavior.
+    ///
+    /// # Safety
+    /// `to` must both be less than `self.len()`
+    #[inline]
+    pub unsafe fn copy_bit_unchecked(&mut self, from: usize, to: usize) {
+        // SAFETY: Caller must ensure that `from` is within bounds.
+        let enabled = self.contains_unchecked(from);
+        // SAFETY: Caller must ensure that `to` is within bounds.
+        self.set_unchecked(to, enabled);
+    }
+
+    /// Count the number of set bits in the given bit range.
+    ///
+    /// This function is potentially much faster than using `ones(other).count()`.
+    /// Use `..` to count the whole content of the bitset.
+    ///
+    /// **Panics** if the range extends past the end of the bitset.
+    #[inline]
+    pub fn count_ones<T: IndexRange>(&self, range: T) -> usize {
+        Self::batch_count_ones(Masks::new(range, self.length).map(|(block, mask)| {
+            // SAFETY: Masks cannot return a block index that is out of range.
+            unsafe { *self.get_unchecked(block) & mask }
+        }))
+    }
+
+    /// Count the number of unset bits in the given bit range.
+    ///
+    /// This function is potentially much faster than using `zeroes(other).count()`.
+    /// Use `..` to count the whole content of the bitset.
+    ///
+    /// **Panics** if the range extends past the end of the bitset.
+    #[inline]
+    pub fn count_zeroes<T: IndexRange>(&self, range: T) -> usize {
+        Self::batch_count_ones(Masks::new(range, self.length).map(|(block, mask)| {
+            // SAFETY: Masks cannot return a block index that is out of range.
+            unsafe { !*self.get_unchecked(block) & mask }
+        }))
+    }
+
+    /// Sets every bit in the given range to the given state (`enabled`)
+    ///
+    /// Use `..` to set the whole bitset.
+    ///
+    /// **Panics** if the range extends past the end of the bitset.
+    #[inline]
+    pub fn set_range<T: IndexRange>(&mut self, range: T, enabled: bool) {
+        if enabled {
+            self.insert_range(range);
+        } else {
+            self.remove_range(range);
+        }
+    }
+
+    /// Enables every bit in the given range.
+    ///
+    /// Use `..` to make the whole bitset ones.
+    ///
+    /// **Panics** if the range extends past the end of the bitset.
+    #[inline]
+    pub fn insert_range<T: IndexRange>(&mut self, range: T) {
+        for (block, mask) in Masks::new(range, self.length) {
+            // SAFETY: Masks cannot return a block index that is out of range.
+            let block = unsafe { self.get_unchecked_mut(block) };
+            *block |= mask;
+        }
+    }
+
+    /// Disables every bit in the given range.
+    ///
+    /// Use `..` to make the whole bitset ones.
+    ///
+    /// **Panics** if the range extends past the end of the bitset.
+    #[inline]
+    pub fn remove_range<T: IndexRange>(&mut self, range: T) {
+        for (block, mask) in Masks::new(range, self.length) {
+            // SAFETY: Masks cannot return a block index that is out of range.
+            let block = unsafe { self.get_unchecked_mut(block) };
+            *block &= !mask;
+        }
+    }
+
+    /// Toggles (inverts) every bit in the given range.
+    ///
+    /// Use `..` to toggle the whole bitset.
+    ///
+    /// **Panics** if the range extends past the end of the bitset.
+    #[inline]
+    pub fn toggle_range<T: IndexRange>(&mut self, range: T) {
+        for (block, mask) in Masks::new(range, self.length) {
+            // SAFETY: Masks cannot return a block index that is out of range.
+            let block = unsafe { self.get_unchecked_mut(block) };
+            *block ^= mask;
+        }
+    }
+
+    /// Checks if the bitset contains every bit in the given range.
+    ///
+    /// **Panics** if the range extends past the end of the bitset.
+    #[inline]
+    pub fn contains_all_in_range<T: IndexRange>(&self, range: T) -> bool {
+        for (block, mask) in Masks::new(range, self.length) {
+            // SAFETY: Masks cannot return a block index that is out of range.
+            let block = unsafe { self.get_unchecked(block) };
+            if block & mask != mask {
+                return false;
+            }
+        }
+        true
+    }
+
+    /// Checks if the bitset contains at least one set bit in the given range.
+    ///
+    /// **Panics** if the range extends past the end of the bitset.
+    #[inline]
+    pub fn contains_any_in_range<T: IndexRange>(&self, range: T) -> bool {
+        for (block, mask) in Masks::new(range, self.length) {
+            // SAFETY: Masks cannot return a block index that is out of range.
+            let block = unsafe { self.get_unchecked(block) };
+            if block & mask != 0 {
+                return true;
+            }
+        }
+        false
+    }
+
+    /// View the bitset as a slice of `Block` blocks
+    #[inline]
+    pub fn as_slice(&self) -> &[Block] {
+        // SAFETY: The bits from both usize and Block are required to be reinterprettable, and
+        // neither have any padding or alignment issues. The slice constructed is within bounds
+        // of the underlying allocation. This function is called with a read-only  borrow so
+        // no other write can happen as long as the returned borrow lives.
+        unsafe {
+            let ptr = self.data.as_ptr().cast::<Block>();
+            core::slice::from_raw_parts(ptr, self.usize_len())
+        }
+    }
+
+    /// View the bitset as a mutable slice of `Block` blocks. Writing past the bitlength in the last
+    /// will cause `contains` to return potentially incorrect results for bits past the bitlength.
+    #[inline]
+    pub fn as_mut_slice(&mut self) -> &mut [Block] {
+        // SAFETY: The bits from both usize and Block are required to be reinterprettable, and
+        // neither have any padding or alignment issues. The slice constructed is within bounds
+        // of the underlying allocation. This function is called with a mutable borrow so
+        // no other read or write can happen as long as the returned borrow lives.
+        unsafe {
+            let ptr = self.data.as_ptr().cast::<Block>();
+            core::slice::from_raw_parts_mut(ptr, self.usize_len())
+        }
+    }
+
+    /// Iterates over all enabled bits.
+    ///
+    /// Iterator element is the index of the `1` bit, type `usize`.
+    #[inline]
+    pub fn ones(&self) -> Ones {
+        match self.as_slice().split_first() {
+            Some((&first_block, rem)) => {
+                let (&last_block, rem) = rem.split_last().unwrap_or((&0, rem));
+                Ones {
+                    bitset_front: first_block,
+                    bitset_back: last_block,
+                    block_idx_front: 0,
+                    block_idx_back: (1 + rem.len()) * BITS,
+                    remaining_blocks: rem.iter(),
+                }
+            }
+            None => Ones {
+                bitset_front: 0,
+                bitset_back: 0,
+                block_idx_front: 0,
+                block_idx_back: 0,
+                remaining_blocks: [].iter(),
+            },
+        }
+    }
+
+    /// Iterates over all enabled bits.
+    ///
+    /// Iterator element is the index of the `1` bit, type `usize`.
+    /// Unlike `ones`, this function consumes the `FixedBitset`.
+    pub fn into_ones(self) -> IntoOnes {
+        let ptr = self.data.as_ptr().cast();
+        let len = self.simd_block_len() * SimdBlock::USIZE_COUNT;
+        // SAFETY:
+        // - ptr comes from self.data, so it is valid;
+        // - self.data is valid for self.data.len() SimdBlocks,
+        //   which is exactly self.data.len() * SimdBlock::USIZE_COUNT usizes;
+        // - we will keep this slice around only as long as self.data is,
+        //   so it won't become dangling.
+        let slice = unsafe { core::slice::from_raw_parts(ptr, len) };
+        // SAFETY: The data pointer and capacity were created from a Vec initially. The block
+        // len is identical to that of the original.
+        let data: Vec<SimdBlock> = unsafe {
+            Vec::from_raw_parts(
+                self.data.as_ptr().cast(),
+                self.simd_block_len(),
+                self.capacity,
+            )
+        };
+        let mut iter = slice.iter().copied();
+
+        core::mem::forget(self);
+
+        IntoOnes {
+            bitset_front: iter.next().unwrap_or(0),
+            bitset_back: iter.next_back().unwrap_or(0),
+            block_idx_front: 0,
+            block_idx_back: len.saturating_sub(1) * BITS,
+            remaining_blocks: iter,
+            _buf: data,
+        }
+    }
+
+    /// Iterates over all disabled bits.
+    ///
+    /// Iterator element is the index of the `0` bit, type `usize`.
+    #[inline]
+    pub fn zeroes(&self) -> Zeroes {
+        match self.as_slice().split_first() {
+            Some((&block, rem)) => Zeroes {
+                bitset: !block,
+                block_idx: 0,
+                len: self.len(),
+                remaining_blocks: rem.iter(),
+            },
+            None => Zeroes {
+                bitset: !0,
+                block_idx: 0,
+                len: self.len(),
+                remaining_blocks: [].iter(),
+            },
+        }
+    }
+
+    /// Returns a lazy iterator over the intersection of two `FixedBitSet`s
+    pub fn intersection<'a>(&'a self, other: &'a FixedBitSet) -> Intersection<'a> {
+        Intersection {
+            iter: self.ones(),
+            other,
+        }
+    }
+
+    /// Returns a lazy iterator over the union of two `FixedBitSet`s.
+    pub fn union<'a>(&'a self, other: &'a FixedBitSet) -> Union<'a> {
+        Union {
+            iter: self.ones().chain(other.difference(self)),
+        }
+    }
+
+    /// Returns a lazy iterator over the difference of two `FixedBitSet`s. The difference of `a`
+    /// and `b` is the elements of `a` which are not in `b`.
+    pub fn difference<'a>(&'a self, other: &'a FixedBitSet) -> Difference<'a> {
+        Difference {
+            iter: self.ones(),
+            other,
+        }
+    }
+
+    /// Returns a lazy iterator over the symmetric difference of two `FixedBitSet`s.
+    /// The symmetric difference of `a` and `b` is the elements of one, but not both, sets.
+    pub fn symmetric_difference<'a>(&'a self, other: &'a FixedBitSet) -> SymmetricDifference<'a> {
+        SymmetricDifference {
+            iter: self.difference(other).chain(other.difference(self)),
+        }
+    }
+
+    /// In-place union of two `FixedBitSet`s.
+    ///
+    /// On calling this method, `self`'s capacity may be increased to match `other`'s.
+    pub fn union_with(&mut self, other: &FixedBitSet) {
+        if other.len() >= self.len() {
+            self.grow(other.len());
+        }
+        self.as_mut_simd_slice()
+            .iter_mut()
+            .zip(other.as_simd_slice().iter())
+            .for_each(|(x, y)| *x |= *y);
+    }
+
+    /// In-place intersection of two `FixedBitSet`s.
+    ///
+    /// On calling this method, `self`'s capacity will remain the same as before.
+    pub fn intersect_with(&mut self, other: &FixedBitSet) {
+        let me = self.as_mut_simd_slice();
+        let other = other.as_simd_slice();
+        me.iter_mut().zip(other.iter()).for_each(|(x, y)| {
+            *x &= *y;
+        });
+        let mn = core::cmp::min(me.len(), other.len());
+        for wd in &mut me[mn..] {
+            *wd = SimdBlock::NONE;
+        }
+    }
+
+    /// In-place difference of two `FixedBitSet`s.
+    ///
+    /// On calling this method, `self`'s capacity will remain the same as before.
+    pub fn difference_with(&mut self, other: &FixedBitSet) {
+        self.as_mut_simd_slice()
+            .iter_mut()
+            .zip(other.as_simd_slice().iter())
+            .for_each(|(x, y)| {
+                *x &= !*y;
+            });
+
+        // There's no need to grow self or do any other adjustments.
+        //
+        // * If self is longer than other, the bits at the end of self won't be affected since other
+        //   has them implicitly set to 0.
+        // * If other is longer than self, the bits at the end of other are irrelevant since self
+        //   has them set to 0 anyway.
+    }
+
+    /// In-place symmetric difference of two `FixedBitSet`s.
+    ///
+    /// On calling this method, `self`'s capacity may be increased to match `other`'s.
+    pub fn symmetric_difference_with(&mut self, other: &FixedBitSet) {
+        if other.len() >= self.len() {
+            self.grow(other.len());
+        }
+        self.as_mut_simd_slice()
+            .iter_mut()
+            .zip(other.as_simd_slice().iter())
+            .for_each(|(x, y)| {
+                *x ^= *y;
+            });
+    }
+
+    /// Computes how many bits would be set in the union between two bitsets.
+    ///
+    /// This is potentially much faster than using `union(other).count()`. Unlike
+    /// other methods like using [`union_with`] followed by [`count_ones`], this
+    /// does not mutate in place or require separate allocations.
+    #[inline]
+    pub fn union_count(&self, other: &FixedBitSet) -> usize {
+        let me = self.as_slice();
+        let other = other.as_slice();
+        let count = Self::batch_count_ones(me.iter().zip(other.iter()).map(|(x, y)| (*x | *y)));
+        match other.len().cmp(&me.len()) {
+            Ordering::Greater => count + Self::batch_count_ones(other[me.len()..].iter().copied()),
+            Ordering::Less => count + Self::batch_count_ones(me[other.len()..].iter().copied()),
+            Ordering::Equal => count,
+        }
+    }
+
+    /// Computes how many bits would be set in the intersection between two bitsets.
+    ///
+    /// This is potentially much faster than using `intersection(other).count()`. Unlike
+    /// other methods like using [`intersect_with`] followed by [`count_ones`], this
+    /// does not mutate in place or require separate allocations.
+    #[inline]
+    pub fn intersection_count(&self, other: &FixedBitSet) -> usize {
+        Self::batch_count_ones(
+            self.as_slice()
+                .iter()
+                .zip(other.as_slice())
+                .map(|(x, y)| (*x & *y)),
+        )
+    }
+
+    /// Computes how many bits would be set in the difference between two bitsets.
+    ///
+    /// This is potentially much faster than using `difference(other).count()`. Unlike
+    /// other methods like using [`difference_with`] followed by [`count_ones`], this
+    /// does not mutate in place or require separate allocations.
+    #[inline]
+    pub fn difference_count(&self, other: &FixedBitSet) -> usize {
+        Self::batch_count_ones(
+            self.as_slice()
+                .iter()
+                .zip(other.as_slice().iter())
+                .map(|(x, y)| (*x & !*y)),
+        )
+    }
+
+    /// Computes how many bits would be set in the symmetric difference between two bitsets.
+    ///
+    /// This is potentially much faster than using `symmetric_difference(other).count()`. Unlike
+    /// other methods like using [`symmetric_difference_with`] followed by [`count_ones`], this
+    /// does not mutate in place or require separate allocations.
+    #[inline]
+    pub fn symmetric_difference_count(&self, other: &FixedBitSet) -> usize {
+        let me = self.as_slice();
+        let other = other.as_slice();
+        let count = Self::batch_count_ones(me.iter().zip(other.iter()).map(|(x, y)| (*x ^ *y)));
+        match other.len().cmp(&me.len()) {
+            Ordering::Greater => count + Self::batch_count_ones(other[me.len()..].iter().copied()),
+            Ordering::Less => count + Self::batch_count_ones(me[other.len()..].iter().copied()),
+            Ordering::Equal => count,
+        }
+    }
+
+    /// Returns `true` if `self` has no elements in common with `other`. This
+    /// is equivalent to checking for an empty intersection.
+    pub fn is_disjoint(&self, other: &FixedBitSet) -> bool {
+        self.as_simd_slice()
+            .iter()
+            .zip(other.as_simd_slice())
+            .all(|(x, y)| (*x & *y).is_empty())
+    }
+
+    /// Returns `true` if the set is a subset of another, i.e. `other` contains
+    /// at least all the values in `self`.
+    pub fn is_subset(&self, other: &FixedBitSet) -> bool {
+        let me = self.as_simd_slice();
+        let other = other.as_simd_slice();
+        me.iter()
+            .zip(other.iter())
+            .all(|(x, y)| x.andnot(*y).is_empty())
+            && me.iter().skip(other.len()).all(|x| x.is_empty())
+    }
+
+    /// Returns `true` if the set is a superset of another, i.e. `self` contains
+    /// at least all the values in `other`.
+    pub fn is_superset(&self, other: &FixedBitSet) -> bool {
+        other.is_subset(self)
+    }
+}
+
+impl Hash for FixedBitSet {
+    fn hash<H: core::hash::Hasher>(&self, state: &mut H) {
+        self.length.hash(state);
+        self.as_simd_slice().hash(state);
+    }
+}
+
+impl PartialEq for FixedBitSet {
+    fn eq(&self, other: &Self) -> bool {
+        self.length == other.length && self.as_simd_slice().eq(other.as_simd_slice())
+    }
+}
+
+impl PartialOrd for FixedBitSet {
+    fn partial_cmp(&self, other: &Self) -> Option<Ordering> {
+        Some(self.cmp(other))
+    }
+}
+
+impl Ord for FixedBitSet {
+    fn cmp(&self, other: &Self) -> Ordering {
+        self.length
+            .cmp(&other.length)
+            .then_with(|| self.as_simd_slice().cmp(other.as_simd_slice()))
+    }
+}
+
+impl Default for FixedBitSet {
+    fn default() -> Self {
+        Self::new()
+    }
+}
+
+impl Drop for FixedBitSet {
+    fn drop(&mut self) {
+        // SAFETY: The data pointer and capacity were created from a Vec initially. The block
+        // len is identical to that of the original.
+        drop(unsafe {
+            Vec::from_raw_parts(self.data.as_ptr(), self.simd_block_len(), self.capacity)
+        });
+    }
+}
+
+impl Binary for FixedBitSet {
+    fn fmt(&self, f: &mut Formatter<'_>) -> Result<(), Error> {
+        if f.alternate() {
+            f.write_str("0b")?;
+        }
+
+        for i in 0..self.length {
+            if self[i] {
+                f.write_char('1')?;
+            } else {
+                f.write_char('0')?;
+            }
+        }
+
+        Ok(())
+    }
+}
+
+impl Display for FixedBitSet {
+    fn fmt(&self, f: &mut Formatter<'_>) -> Result<(), Error> {
+        Binary::fmt(&self, f)
+    }
+}
+
+/// An iterator producing elements in the difference of two sets.
+///
+/// This struct is created by the [`FixedBitSet::difference`] method.
+pub struct Difference<'a> {
+    iter: Ones<'a>,
+    other: &'a FixedBitSet,
+}
+
+impl<'a> Iterator for Difference<'a> {
+    type Item = usize;
+
+    #[inline]
+    fn next(&mut self) -> Option<Self::Item> {
+        self.iter.by_ref().find(|&nxt| !self.other.contains(nxt))
+    }
+
+    #[inline]
+    fn size_hint(&self) -> (usize, Option<usize>) {
+        self.iter.size_hint()
+    }
+}
+
+impl<'a> DoubleEndedIterator for Difference<'a> {
+    fn next_back(&mut self) -> Option<Self::Item> {
+        self.iter
+            .by_ref()
+            .rev()
+            .find(|&nxt| !self.other.contains(nxt))
+    }
+}
+
+// Difference will continue to return None once it first returns None.
+impl<'a> FusedIterator for Difference<'a> {}
+
+/// An iterator producing elements in the symmetric difference of two sets.
+///
+/// This struct is created by the [`FixedBitSet::symmetric_difference`] method.
+pub struct SymmetricDifference<'a> {
+    iter: Chain<Difference<'a>, Difference<'a>>,
+}
+
+impl<'a> Iterator for SymmetricDifference<'a> {
+    type Item = usize;
+
+    #[inline]
+    fn next(&mut self) -> Option<Self::Item> {
+        self.iter.next()
+    }
+
+    #[inline]
+    fn size_hint(&self) -> (usize, Option<usize>) {
+        self.iter.size_hint()
+    }
+}
+
+impl<'a> DoubleEndedIterator for SymmetricDifference<'a> {
+    fn next_back(&mut self) -> Option<Self::Item> {
+        self.iter.next_back()
+    }
+}
+
+// SymmetricDifference will continue to return None once it first returns None.
+impl<'a> FusedIterator for SymmetricDifference<'a> {}
+
+/// An iterator producing elements in the intersection of two sets.
+///
+/// This struct is created by the [`FixedBitSet::intersection`] method.
+pub struct Intersection<'a> {
+    iter: Ones<'a>,
+    other: &'a FixedBitSet,
+}
+
+impl<'a> Iterator for Intersection<'a> {
+    type Item = usize; // the bit position of the '1'
+
+    #[inline]
+    fn next(&mut self) -> Option<Self::Item> {
+        self.iter.by_ref().find(|&nxt| self.other.contains(nxt))
+    }
+
+    #[inline]
+    fn size_hint(&self) -> (usize, Option<usize>) {
+        self.iter.size_hint()
+    }
+}
+
+impl<'a> DoubleEndedIterator for Intersection<'a> {
+    fn next_back(&mut self) -> Option<Self::Item> {
+        self.iter
+            .by_ref()
+            .rev()
+            .find(|&nxt| self.other.contains(nxt))
+    }
+}
+
+// Intersection will continue to return None once it first returns None.
+impl<'a> FusedIterator for Intersection<'a> {}
+
+/// An iterator producing elements in the union of two sets.
+///
+/// This struct is created by the [`FixedBitSet::union`] method.
+pub struct Union<'a> {
+    iter: Chain<Ones<'a>, Difference<'a>>,
+}
+
+impl<'a> Iterator for Union<'a> {
+    type Item = usize;
+
+    #[inline]
+    fn next(&mut self) -> Option<Self::Item> {
+        self.iter.next()
+    }
+
+    #[inline]
+    fn size_hint(&self) -> (usize, Option<usize>) {
+        self.iter.size_hint()
+    }
+}
+
+impl<'a> DoubleEndedIterator for Union<'a> {
+    fn next_back(&mut self) -> Option<Self::Item> {
+        self.iter.next_back()
+    }
+}
+
+// Union will continue to return None once it first returns None.
+impl<'a> FusedIterator for Union<'a> {}
+
+struct Masks {
+    first_block: usize,
+    first_mask: usize,
+    last_block: usize,
+    last_mask: usize,
+}
+
+impl Masks {
+    #[inline]
+    fn new<T: IndexRange>(range: T, length: usize) -> Masks {
+        let start = range.start().unwrap_or(0);
+        let end = range.end().unwrap_or(length);
+        assert!(
+            start <= end && end <= length,
+            "invalid range {}..{} for a fixedbitset of size {}",
+            start,
+            end,
+            length
+        );
+
+        let (first_block, first_rem) = div_rem(start, BITS);
+        let (last_block, last_rem) = div_rem(end, BITS);
+
+        Masks {
+            first_block,
+            first_mask: usize::MAX << first_rem,
+            last_block,
+            last_mask: (usize::MAX >> 1) >> (BITS - last_rem - 1),
+            // this is equivalent to `MAX >> (BITS - x)` with correct semantics when x == 0.
+        }
+    }
+}
+
+impl Iterator for Masks {
+    type Item = (usize, usize);
+
+    #[inline]
+    fn next(&mut self) -> Option<Self::Item> {
+        match self.first_block.cmp(&self.last_block) {
+            Ordering::Less => {
+                let res = (self.first_block, self.first_mask);
+                self.first_block += 1;
+                self.first_mask = !0;
+                Some(res)
+            }
+            Ordering::Equal => {
+                let mask = self.first_mask & self.last_mask;
+                let res = if mask == 0 {
+                    None
+                } else {
+                    Some((self.first_block, mask))
+                };
+                self.first_block += 1;
+                res
+            }
+            Ordering::Greater => None,
+        }
+    }
+
+    #[inline]
+    fn size_hint(&self) -> (usize, Option<usize>) {
+        (self.first_block..=self.last_block).size_hint()
+    }
+}
+
+// Masks will continue to return None once it first returns None.
+impl FusedIterator for Masks {}
+
+// Masks's size_hint implementation is exact. It never returns an
+// unbounded value and always returns an exact number of values.
+impl ExactSizeIterator for Masks {}
+
+/// An  iterator producing the indices of the set bit in a set.
+///
+/// This struct is created by the [`FixedBitSet::ones`] method.
+pub struct Ones<'a> {
+    bitset_front: usize,
+    bitset_back: usize,
+    block_idx_front: usize,
+    block_idx_back: usize,
+    remaining_blocks: core::slice::Iter<'a, usize>,
+}
+
+impl<'a> Ones<'a> {
+    #[inline]
+    pub fn last_positive_bit_and_unset(n: &mut usize) -> usize {
+        // Find the last set bit using x & -x
+        let last_bit = *n & n.wrapping_neg();
+
+        // Find the position of the last set bit
+        let position = last_bit.trailing_zeros();
+
+        // Unset the last set bit
+        *n &= *n - 1;
+
+        position as usize
+    }
+
+    #[inline]
+    fn first_positive_bit_and_unset(n: &mut usize) -> usize {
+        /* Identify the first non zero bit */
+        let bit_idx = n.leading_zeros();
+
+        /* set that bit to zero */
+        let mask = !((1_usize) << (BITS as u32 - bit_idx - 1));
+        n.bitand_assign(mask);
+
+        bit_idx as usize
+    }
+}
+
+impl<'a> DoubleEndedIterator for Ones<'a> {
+    fn next_back(&mut self) -> Option<Self::Item> {
+        while self.bitset_back == 0 {
+            match self.remaining_blocks.next_back() {
+                None => {
+                    if self.bitset_front != 0 {
+                        self.bitset_back = 0;
+                        self.block_idx_back = self.block_idx_front;
+                        return Some(
+                            self.block_idx_front + BITS
+                                - Self::first_positive_bit_and_unset(&mut self.bitset_front)
+                                - 1,
+                        );
+                    } else {
+                        return None;
+                    }
+                }
+                Some(next_block) => {
+                    self.bitset_back = *next_block;
+                    self.block_idx_back -= BITS;
+                }
+            };
+        }
+
+        Some(
+            self.block_idx_back - Self::first_positive_bit_and_unset(&mut self.bitset_back) + BITS
+                - 1,
+        )
+    }
+}
+
+impl<'a> Iterator for Ones<'a> {
+    type Item = usize; // the bit position of the '1'
+
+    #[inline]
+    fn next(&mut self) -> Option<Self::Item> {
+        while self.bitset_front == 0 {
+            match self.remaining_blocks.next() {
+                Some(next_block) => {
+                    self.bitset_front = *next_block;
+                    self.block_idx_front += BITS;
+                }
+                None => {
+                    if self.bitset_back != 0 {
+                        // not needed for iteration, but for size_hint
+                        self.block_idx_front = self.block_idx_back;
+                        self.bitset_front = 0;
+
+                        return Some(
+                            self.block_idx_back
+                                + Self::last_positive_bit_and_unset(&mut self.bitset_back),
+                        );
+                    } else {
+                        return None;
+                    }
+                }
+            };
+        }
+
+        Some(self.block_idx_front + Self::last_positive_bit_and_unset(&mut self.bitset_front))
+    }
+
+    #[inline]
+    fn size_hint(&self) -> (usize, Option<usize>) {
+        (
+            0,
+            (Some(self.block_idx_back - self.block_idx_front + 2 * BITS)),
+        )
+    }
+}
+
+// Ones will continue to return None once it first returns None.
+impl<'a> FusedIterator for Ones<'a> {}
+
+/// An  iterator producing the indices of the set bit in a set.
+///
+/// This struct is created by the [`FixedBitSet::ones`] method.
+pub struct Zeroes<'a> {
+    bitset: usize,
+    block_idx: usize,
+    len: usize,
+    remaining_blocks: core::slice::Iter<'a, usize>,
+}
+
+impl<'a> Iterator for Zeroes<'a> {
+    type Item = usize; // the bit position of the '1'
+
+    #[inline]
+    fn next(&mut self) -> Option<Self::Item> {
+        while self.bitset == 0 {
+            self.bitset = !*self.remaining_blocks.next()?;
+            self.block_idx += BITS;
+        }
+        let t = self.bitset & (0_usize).wrapping_sub(self.bitset);
+        let r = self.bitset.trailing_zeros() as usize;
+        self.bitset ^= t;
+        let bit = self.block_idx + r;
+        // The remaining zeroes beyond the length of the bitset must be excluded.
+        if bit < self.len {
+            Some(bit)
+        } else {
+            None
+        }
+    }
+
+    #[inline]
+    fn size_hint(&self) -> (usize, Option<usize>) {
+        (0, Some(self.len))
+    }
+}
+
+// Zeroes will stop returning Some when exhausted.
+impl<'a> FusedIterator for Zeroes<'a> {}
+
+impl Clone for FixedBitSet {
+    #[inline]
+    fn clone(&self) -> Self {
+        Self::from_blocks_and_len(Vec::from(self.as_simd_slice()), self.length)
+    }
+
+    #[inline]
+    fn clone_from(&mut self, source: &Self) {
+        if self.length < source.length {
+            // SAFETY: `fill` is uninitialized, but is immediately initialized from `source`.
+            unsafe { self.grow_inner(source.length, MaybeUninit::uninit()) };
+        }
+        let me = self.as_mut_simd_slice_uninit();
+        let them = source.as_simd_slice_uninit();
+        match me.len().cmp(&them.len()) {
+            Ordering::Greater => {
+                let (head, tail) = me.split_at_mut(them.len());
+                head.copy_from_slice(them);
+                tail.fill(MaybeUninit::new(SimdBlock::NONE));
+            }
+            Ordering::Equal => me.copy_from_slice(them),
+            // The grow_inner above ensures that self is at least as large as source.
+            // so this branch is unreachable.
+            Ordering::Less => {}
+        }
+        self.length = source.length;
+    }
+}
+
+/// Return **true** if the bit is enabled in the bitset,
+/// or **false** otherwise.
+///
+/// Note: bits outside the capacity are always disabled, and thus
+/// indexing a FixedBitSet will not panic.
+impl Index<usize> for FixedBitSet {
+    type Output = bool;
+
+    #[inline]
+    fn index(&self, bit: usize) -> &bool {
+        if self.contains(bit) {
+            &true
+        } else {
+            &false
+        }
+    }
+}
+
+/// Sets the bit at index **i** to **true** for each item **i** in the input **src**.
+impl Extend<usize> for FixedBitSet {
+    fn extend<I: IntoIterator<Item = usize>>(&mut self, src: I) {
+        let iter = src.into_iter();
+        for i in iter {
+            if i >= self.len() {
+                self.grow(i + 1);
+            }
+            self.put(i);
+        }
+    }
+}
+
+/// Return a FixedBitSet containing bits set to **true** for every bit index in
+/// the iterator, other bits are set to **false**.
+impl FromIterator<usize> for FixedBitSet {
+    fn from_iter<I: IntoIterator<Item = usize>>(src: I) -> Self {
+        let mut fbs = FixedBitSet::with_capacity(0);
+        fbs.extend(src);
+        fbs
+    }
+}
+
+pub struct IntoOnes {
+    bitset_front: Block,
+    bitset_back: Block,
+    block_idx_front: usize,
+    block_idx_back: usize,
+    remaining_blocks: core::iter::Copied<core::slice::Iter<'static, usize>>,
+    // Keep buf along so that `remaining_blocks` remains valid.
+    _buf: Vec<SimdBlock>,
+}
+
+impl IntoOnes {
+    #[inline]
+    pub fn last_positive_bit_and_unset(n: &mut Block) -> usize {
+        // Find the last set bit using x & -x
+        let last_bit = *n & n.wrapping_neg();
+
+        // Find the position of the last set bit
+        let position = last_bit.trailing_zeros();
+
+        // Unset the last set bit
+        *n &= *n - 1;
+
+        position as usize
+    }
+
+    #[inline]
+    fn first_positive_bit_and_unset(n: &mut Block) -> usize {
+        /* Identify the first non zero bit */
+        let bit_idx = n.leading_zeros();
+
+        /* set that bit to zero */
+        let mask = !((1_usize) << (BITS as u32 - bit_idx - 1));
+        n.bitand_assign(mask);
+
+        bit_idx as usize
+    }
+}
+
+impl DoubleEndedIterator for IntoOnes {
+    fn next_back(&mut self) -> Option<Self::Item> {
+        while self.bitset_back == 0 {
+            match self.remaining_blocks.next_back() {
+                None => {
+                    if self.bitset_front != 0 {
+                        self.bitset_back = 0;
+                        self.block_idx_back = self.block_idx_front;
+                        return Some(
+                            self.block_idx_front + BITS
+                                - Self::first_positive_bit_and_unset(&mut self.bitset_front)
+                                - 1,
+                        );
+                    } else {
+                        return None;
+                    }
+                }
+                Some(next_block) => {
+                    self.bitset_back = next_block;
+                    self.block_idx_back -= BITS;
+                }
+            };
+        }
+
+        Some(
+            self.block_idx_back - Self::first_positive_bit_and_unset(&mut self.bitset_back) + BITS
+                - 1,
+        )
+    }
+}
+
+impl Iterator for IntoOnes {
+    type Item = usize; // the bit position of the '1'
+
+    #[inline]
+    fn next(&mut self) -> Option<Self::Item> {
+        while self.bitset_front == 0 {
+            match self.remaining_blocks.next() {
+                Some(next_block) => {
+                    self.bitset_front = next_block;
+                    self.block_idx_front += BITS;
+                }
+                None => {
+                    if self.bitset_back != 0 {
+                        // not needed for iteration, but for size_hint
+                        self.block_idx_front = self.block_idx_back;
+                        self.bitset_front = 0;
+
+                        return Some(
+                            self.block_idx_back
+                                + Self::last_positive_bit_and_unset(&mut self.bitset_back),
+                        );
+                    } else {
+                        return None;
+                    }
+                }
+            };
+        }
+
+        Some(self.block_idx_front + Self::last_positive_bit_and_unset(&mut self.bitset_front))
+    }
+
+    #[inline]
+    fn size_hint(&self) -> (usize, Option<usize>) {
+        (
+            0,
+            (Some(self.block_idx_back - self.block_idx_front + 2 * BITS)),
+        )
+    }
+}
+
+// Ones will continue to return None once it first returns None.
+impl FusedIterator for IntoOnes {}
+
+impl<'a> BitAnd for &'a FixedBitSet {
+    type Output = FixedBitSet;
+    fn bitand(self, other: &FixedBitSet) -> FixedBitSet {
+        let (short, long) = {
+            if self.len() <= other.len() {
+                (self.as_simd_slice(), other.as_simd_slice())
+            } else {
+                (other.as_simd_slice(), self.as_simd_slice())
+            }
+        };
+        let mut data = Vec::from(short);
+        for (data, block) in data.iter_mut().zip(long.iter()) {
+            *data &= *block;
+        }
+        let len = core::cmp::min(self.len(), other.len());
+        FixedBitSet::from_blocks_and_len(data, len)
+    }
+}
+
+impl BitAndAssign for FixedBitSet {
+    fn bitand_assign(&mut self, other: Self) {
+        self.intersect_with(&other);
+    }
+}
+
+impl BitAndAssign<&Self> for FixedBitSet {
+    fn bitand_assign(&mut self, other: &Self) {
+        self.intersect_with(other);
+    }
+}
+
+impl<'a> BitOr for &'a FixedBitSet {
+    type Output = FixedBitSet;
+    fn bitor(self, other: &FixedBitSet) -> FixedBitSet {
+        let (short, long) = {
+            if self.len() <= other.len() {
+                (self.as_simd_slice(), other.as_simd_slice())
+            } else {
+                (other.as_simd_slice(), self.as_simd_slice())
+            }
+        };
+        let mut data = Vec::from(long);
+        for (data, block) in data.iter_mut().zip(short.iter()) {
+            *data |= *block;
+        }
+        let len = core::cmp::max(self.len(), other.len());
+        FixedBitSet::from_blocks_and_len(data, len)
+    }
+}
+
+impl BitOrAssign for FixedBitSet {
+    fn bitor_assign(&mut self, other: Self) {
+        self.union_with(&other);
+    }
+}
+
+impl BitOrAssign<&Self> for FixedBitSet {
+    fn bitor_assign(&mut self, other: &Self) {
+        self.union_with(other);
+    }
+}
+
+impl<'a> BitXor for &'a FixedBitSet {
+    type Output = FixedBitSet;
+    fn bitxor(self, other: &FixedBitSet) -> FixedBitSet {
+        let (short, long) = {
+            if self.len() <= other.len() {
+                (self.as_simd_slice(), other.as_simd_slice())
+            } else {
+                (other.as_simd_slice(), self.as_simd_slice())
+            }
+        };
+        let mut data = Vec::from(long);
+        for (data, block) in data.iter_mut().zip(short.iter()) {
+            *data ^= *block;
+        }
+        let len = core::cmp::max(self.len(), other.len());
+        FixedBitSet::from_blocks_and_len(data, len)
+    }
+}
+
+impl BitXorAssign for FixedBitSet {
+    fn bitxor_assign(&mut self, other: Self) {
+        self.symmetric_difference_with(&other);
+    }
+}
+
+impl BitXorAssign<&Self> for FixedBitSet {
+    fn bitxor_assign(&mut self, other: &Self) {
+        self.symmetric_difference_with(other);
+    }
+}