Adding upstream version 0.70.1+ds1.upstream/0.70.1+ds1upstream

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

6 files changed, 5127 insertions, 0 deletions

diff --git a/vendor/hashbrown/src/raw/alloc.rs b/vendor/hashbrown/src/raw/alloc.rs
new file mode 100644
index 0000000..15299e7
--- /dev/null
+++ b/vendor/hashbrown/src/raw/alloc.rs
@@ -0,0 +1,86 @@
+pub(crate) use self::inner::{do_alloc, Allocator, Global};
+
+// Nightly-case.
+// Use unstable `allocator_api` feature.
+// This is compatible with `allocator-api2` which can be enabled or not.
+// This is used when building for `std`.
+#[cfg(feature = "nightly")]
+mod inner {
+    use crate::alloc::alloc::Layout;
+    pub use crate::alloc::alloc::{Allocator, Global};
+    use core::ptr::NonNull;
+
+    #[allow(clippy::map_err_ignore)]
+    pub(crate) fn do_alloc<A: Allocator>(alloc: &A, layout: Layout) -> Result<NonNull<u8>, ()> {
+        match alloc.allocate(layout) {
+            Ok(ptr) => Ok(ptr.as_non_null_ptr()),
+            Err(_) => Err(()),
+        }
+    }
+}
+
+// Basic non-nightly case.
+// This uses `allocator-api2` enabled by default.
+// If any crate enables "nightly" in `allocator-api2`,
+// this will be equivalent to the nightly case,
+// since `allocator_api2::alloc::Allocator` would be re-export of
+// `core::alloc::Allocator`.
+#[cfg(all(not(feature = "nightly"), feature = "allocator-api2"))]
+mod inner {
+    use crate::alloc::alloc::Layout;
+    pub use allocator_api2::alloc::{Allocator, Global};
+    use core::ptr::NonNull;
+
+    #[allow(clippy::map_err_ignore)]
+    pub(crate) fn do_alloc<A: Allocator>(alloc: &A, layout: Layout) -> Result<NonNull<u8>, ()> {
+        match alloc.allocate(layout) {
+            Ok(ptr) => Ok(ptr.cast()),
+            Err(_) => Err(()),
+        }
+    }
+}
+
+// No-defaults case.
+// When building with default-features turned off and
+// neither `nightly` nor `allocator-api2` is enabled,
+// this will be used.
+// Making it impossible to use any custom allocator with collections defined
+// in this crate.
+// Any crate in build-tree can enable `allocator-api2`,
+// or `nightly` without disturbing users that don't want to use it.
+#[cfg(not(any(feature = "nightly", feature = "allocator-api2")))]
+mod inner {
+    use crate::alloc::alloc::{alloc, dealloc, Layout};
+    use core::ptr::NonNull;
+
+    #[allow(clippy::missing_safety_doc)] // not exposed outside of this crate
+    pub unsafe trait Allocator {
+        fn allocate(&self, layout: Layout) -> Result<NonNull<u8>, ()>;
+        unsafe fn deallocate(&self, ptr: NonNull<u8>, layout: Layout);
+    }
+
+    #[derive(Copy, Clone)]
+    pub struct Global;
+
+    unsafe impl Allocator for Global {
+        #[inline]
+        fn allocate(&self, layout: Layout) -> Result<NonNull<u8>, ()> {
+            unsafe { NonNull::new(alloc(layout)).ok_or(()) }
+        }
+        #[inline]
+        unsafe fn deallocate(&self, ptr: NonNull<u8>, layout: Layout) {
+            dealloc(ptr.as_ptr(), layout);
+        }
+    }
+
+    impl Default for Global {
+        #[inline]
+        fn default() -> Self {
+            Global
+        }
+    }
+
+    pub(crate) fn do_alloc<A: Allocator>(alloc: &A, layout: Layout) -> Result<NonNull<u8>, ()> {
+        alloc.allocate(layout)
+    }
+}
diff --git a/vendor/hashbrown/src/raw/bitmask.rs b/vendor/hashbrown/src/raw/bitmask.rs
new file mode 100644
index 0000000..6576b3c
--- /dev/null
+++ b/vendor/hashbrown/src/raw/bitmask.rs
@@ -0,0 +1,133 @@
+use super::imp::{
+    BitMaskWord, NonZeroBitMaskWord, BITMASK_ITER_MASK, BITMASK_MASK, BITMASK_STRIDE,
+};
+
+/// A bit mask which contains the result of a `Match` operation on a `Group` and
+/// allows iterating through them.
+///
+/// The bit mask is arranged so that low-order bits represent lower memory
+/// addresses for group match results.
+///
+/// For implementation reasons, the bits in the set may be sparsely packed with
+/// groups of 8 bits representing one element. If any of these bits are non-zero
+/// then this element is considered to true in the mask. If this is the
+/// case, `BITMASK_STRIDE` will be 8 to indicate a divide-by-8 should be
+/// performed on counts/indices to normalize this difference. `BITMASK_MASK` is
+/// similarly a mask of all the actually-used bits.
+///
+/// To iterate over a bit mask, it must be converted to a form where only 1 bit
+/// is set per element. This is done by applying `BITMASK_ITER_MASK` on the
+/// mask bits.
+#[derive(Copy, Clone)]
+pub(crate) struct BitMask(pub(crate) BitMaskWord);
+
+#[allow(clippy::use_self)]
+impl BitMask {
+    /// Returns a new `BitMask` with all bits inverted.
+    #[inline]
+    #[must_use]
+    #[allow(dead_code)]
+    pub(crate) fn invert(self) -> Self {
+        BitMask(self.0 ^ BITMASK_MASK)
+    }
+
+    /// Returns a new `BitMask` with the lowest bit removed.
+    #[inline]
+    #[must_use]
+    fn remove_lowest_bit(self) -> Self {
+        BitMask(self.0 & (self.0 - 1))
+    }
+
+    /// Returns whether the `BitMask` has at least one set bit.
+    #[inline]
+    pub(crate) fn any_bit_set(self) -> bool {
+        self.0 != 0
+    }
+
+    /// Returns the first set bit in the `BitMask`, if there is one.
+    #[inline]
+    pub(crate) fn lowest_set_bit(self) -> Option<usize> {
+        if let Some(nonzero) = NonZeroBitMaskWord::new(self.0) {
+            Some(Self::nonzero_trailing_zeros(nonzero))
+        } else {
+            None
+        }
+    }
+
+    /// Returns the number of trailing zeroes in the `BitMask`.
+    #[inline]
+    pub(crate) fn trailing_zeros(self) -> usize {
+        // ARM doesn't have a trailing_zeroes instruction, and instead uses
+        // reverse_bits (RBIT) + leading_zeroes (CLZ). However older ARM
+        // versions (pre-ARMv7) don't have RBIT and need to emulate it
+        // instead. Since we only have 1 bit set in each byte on ARM, we can
+        // use swap_bytes (REV) + leading_zeroes instead.
+        if cfg!(target_arch = "arm") && BITMASK_STRIDE % 8 == 0 {
+            self.0.swap_bytes().leading_zeros() as usize / BITMASK_STRIDE
+        } else {
+            self.0.trailing_zeros() as usize / BITMASK_STRIDE
+        }
+    }
+
+    /// Same as above but takes a `NonZeroBitMaskWord`.
+    #[inline]
+    fn nonzero_trailing_zeros(nonzero: NonZeroBitMaskWord) -> usize {
+        if cfg!(target_arch = "arm") && BITMASK_STRIDE % 8 == 0 {
+            // SAFETY: A byte-swapped non-zero value is still non-zero.
+            let swapped = unsafe { NonZeroBitMaskWord::new_unchecked(nonzero.get().swap_bytes()) };
+            swapped.leading_zeros() as usize / BITMASK_STRIDE
+        } else {
+            nonzero.trailing_zeros() as usize / BITMASK_STRIDE
+        }
+    }
+
+    /// Returns the number of leading zeroes in the `BitMask`.
+    #[inline]
+    pub(crate) fn leading_zeros(self) -> usize {
+        self.0.leading_zeros() as usize / BITMASK_STRIDE
+    }
+}
+
+impl IntoIterator for BitMask {
+    type Item = usize;
+    type IntoIter = BitMaskIter;
+
+    #[inline]
+    fn into_iter(self) -> BitMaskIter {
+        // A BitMask only requires each element (group of bits) to be non-zero.
+        // However for iteration we need each element to only contain 1 bit.
+        BitMaskIter(BitMask(self.0 & BITMASK_ITER_MASK))
+    }
+}
+
+/// Iterator over the contents of a `BitMask`, returning the indices of set
+/// bits.
+#[derive(Copy, Clone)]
+pub(crate) struct BitMaskIter(pub(crate) BitMask);
+
+impl BitMaskIter {
+    /// Flip the bit in the mask for the entry at the given index.
+    ///
+    /// Returns the bit's previous state.
+    #[inline]
+    #[allow(clippy::cast_ptr_alignment)]
+    #[cfg(feature = "raw")]
+    pub(crate) unsafe fn flip(&mut self, index: usize) -> bool {
+        // NOTE: The + BITMASK_STRIDE - 1 is to set the high bit.
+        let mask = 1 << (index * BITMASK_STRIDE + BITMASK_STRIDE - 1);
+        self.0 .0 ^= mask;
+        // The bit was set if the bit is now 0.
+        self.0 .0 & mask == 0
+    }
+}
+
+impl Iterator for BitMaskIter {
+    type Item = usize;
+
+    #[inline]
+    fn next(&mut self) -> Option<usize> {
+        let bit = self.0.lowest_set_bit()?;
+        self.0 = self.0.remove_lowest_bit();
+        Some(bit)
+    }
+}
diff --git a/vendor/hashbrown/src/raw/generic.rs b/vendor/hashbrown/src/raw/generic.rs
new file mode 100644
index 0000000..c668b06
--- /dev/null
+++ b/vendor/hashbrown/src/raw/generic.rs
@@ -0,0 +1,157 @@
+use super::bitmask::BitMask;
+use super::EMPTY;
+use core::{mem, ptr};
+
+// Use the native word size as the group size. Using a 64-bit group size on
+// a 32-bit architecture will just end up being more expensive because
+// shifts and multiplies will need to be emulated.
+
+cfg_if! {
+    if #[cfg(any(
+        target_pointer_width = "64",
+        target_arch = "aarch64",
+        target_arch = "x86_64",
+        target_arch = "wasm32",
+    ))] {
+        type GroupWord = u64;
+        type NonZeroGroupWord = core::num::NonZeroU64;
+    } else {
+        type GroupWord = u32;
+        type NonZeroGroupWord = core::num::NonZeroU32;
+    }
+}
+
+pub(crate) type BitMaskWord = GroupWord;
+pub(crate) type NonZeroBitMaskWord = NonZeroGroupWord;
+pub(crate) const BITMASK_STRIDE: usize = 8;
+// We only care about the highest bit of each byte for the mask.
+#[allow(clippy::cast_possible_truncation, clippy::unnecessary_cast)]
+pub(crate) const BITMASK_MASK: BitMaskWord = 0x8080_8080_8080_8080_u64 as GroupWord;
+pub(crate) const BITMASK_ITER_MASK: BitMaskWord = !0;
+
+/// Helper function to replicate a byte across a `GroupWord`.
+#[inline]
+fn repeat(byte: u8) -> GroupWord {
+    GroupWord::from_ne_bytes([byte; Group::WIDTH])
+}
+
+/// Abstraction over a group of control bytes which can be scanned in
+/// parallel.
+///
+/// This implementation uses a word-sized integer.
+#[derive(Copy, Clone)]
+pub(crate) struct Group(GroupWord);
+
+// We perform all operations in the native endianness, and convert to
+// little-endian just before creating a BitMask. The can potentially
+// enable the compiler to eliminate unnecessary byte swaps if we are
+// only checking whether a BitMask is empty.
+#[allow(clippy::use_self)]
+impl Group {
+    /// Number of bytes in the group.
+    pub(crate) const WIDTH: usize = mem::size_of::<Self>();
+
+    /// Returns a full group of empty bytes, suitable for use as the initial
+    /// value for an empty hash table.
+    ///
+    /// This is guaranteed to be aligned to the group size.
+    #[inline]
+    pub(crate) const fn static_empty() -> &'static [u8; Group::WIDTH] {
+        #[repr(C)]
+        struct AlignedBytes {
+            _align: [Group; 0],
+            bytes: [u8; Group::WIDTH],
+        }
+        const ALIGNED_BYTES: AlignedBytes = AlignedBytes {
+            _align: [],
+            bytes: [EMPTY; Group::WIDTH],
+        };
+        &ALIGNED_BYTES.bytes
+    }
+
+    /// Loads a group of bytes starting at the given address.
+    #[inline]
+    #[allow(clippy::cast_ptr_alignment)] // unaligned load
+    pub(crate) unsafe fn load(ptr: *const u8) -> Self {
+        Group(ptr::read_unaligned(ptr.cast()))
+    }
+
+    /// Loads a group of bytes starting at the given address, which must be
+    /// aligned to `mem::align_of::<Group>()`.
+    #[inline]
+    #[allow(clippy::cast_ptr_alignment)]
+    pub(crate) unsafe fn load_aligned(ptr: *const u8) -> Self {
+        // FIXME: use align_offset once it stabilizes
+        debug_assert_eq!(ptr as usize & (mem::align_of::<Self>() - 1), 0);
+        Group(ptr::read(ptr.cast()))
+    }
+
+    /// Stores the group of bytes to the given address, which must be
+    /// aligned to `mem::align_of::<Group>()`.
+    #[inline]
+    #[allow(clippy::cast_ptr_alignment)]
+    pub(crate) unsafe fn store_aligned(self, ptr: *mut u8) {
+        // FIXME: use align_offset once it stabilizes
+        debug_assert_eq!(ptr as usize & (mem::align_of::<Self>() - 1), 0);
+        ptr::write(ptr.cast(), self.0);
+    }
+
+    /// Returns a `BitMask` indicating all bytes in the group which *may*
+    /// have the given value.
+    ///
+    /// This function may return a false positive in certain cases where
+    /// the byte in the group differs from the searched value only in its
+    /// lowest bit. This is fine because:
+    /// - This never happens for `EMPTY` and `DELETED`, only full entries.
+    /// - The check for key equality will catch these.
+    /// - This only happens if there is at least 1 true match.
+    /// - The chance of this happening is very low (< 1% chance per byte).
+    #[inline]
+    pub(crate) fn match_byte(self, byte: u8) -> BitMask {
+        // This algorithm is derived from
+        // https://graphics.stanford.edu/~seander/bithacks.html##ValueInWord
+        let cmp = self.0 ^ repeat(byte);
+        BitMask((cmp.wrapping_sub(repeat(0x01)) & !cmp & repeat(0x80)).to_le())
+    }
+
+    /// Returns a `BitMask` indicating all bytes in the group which are
+    /// `EMPTY`.
+    #[inline]
+    pub(crate) fn match_empty(self) -> BitMask {
+        // If the high bit is set, then the byte must be either:
+        // 1111_1111 (EMPTY) or 1000_0000 (DELETED).
+        // So we can just check if the top two bits are 1 by ANDing them.
+        BitMask((self.0 & (self.0 << 1) & repeat(0x80)).to_le())
+    }
+
+    /// Returns a `BitMask` indicating all bytes in the group which are
+    /// `EMPTY` or `DELETED`.
+    #[inline]
+    pub(crate) fn match_empty_or_deleted(self) -> BitMask {
+        // A byte is EMPTY or DELETED iff the high bit is set
+        BitMask((self.0 & repeat(0x80)).to_le())
+    }
+
+    /// Returns a `BitMask` indicating all bytes in the group which are full.
+    #[inline]
+    pub(crate) fn match_full(self) -> BitMask {
+        self.match_empty_or_deleted().invert()
+    }
+
+    /// Performs the following transformation on all bytes in the group:
+    /// - `EMPTY => EMPTY`
+    /// - `DELETED => EMPTY`
+    /// - `FULL => DELETED`
+    #[inline]
+    pub(crate) fn convert_special_to_empty_and_full_to_deleted(self) -> Self {
+        // Map high_bit = 1 (EMPTY or DELETED) to 1111_1111
+        // and high_bit = 0 (FULL) to 1000_0000
+        //
+        // Here's this logic expanded to concrete values:
+        //   let full = 1000_0000 (true) or 0000_0000 (false)
+        //   !1000_0000 + 1 = 0111_1111 + 1 = 1000_0000 (no carry)
+        //   !0000_0000 + 0 = 1111_1111 + 0 = 1111_1111 (no carry)
+        let full = !self.0 & repeat(0x80);
+        Group(!full + (full >> 7))
+    }
+}
diff --git a/vendor/hashbrown/src/raw/mod.rs b/vendor/hashbrown/src/raw/mod.rs
new file mode 100644
index 0000000..789c3a5
--- /dev/null
+++ b/vendor/hashbrown/src/raw/mod.rs
@@ -0,0 +1,4478 @@
+use crate::alloc::alloc::{handle_alloc_error, Layout};
+use crate::scopeguard::{guard, ScopeGuard};
+use crate::TryReserveError;
+use core::iter::FusedIterator;
+use core::marker::PhantomData;
+use core::mem;
+use core::mem::MaybeUninit;
+use core::ptr::NonNull;
+use core::{hint, ptr};
+
+cfg_if! {
+    // Use the SSE2 implementation if possible: it allows us to scan 16 buckets
+    // at once instead of 8. We don't bother with AVX since it would require
+    // runtime dispatch and wouldn't gain us much anyways: the probability of
+    // finding a match drops off drastically after the first few buckets.
+    //
+    // I attempted an implementation on ARM using NEON instructions, but it
+    // turns out that most NEON instructions have multi-cycle latency, which in
+    // the end outweighs any gains over the generic implementation.
+    if #[cfg(all(
+        target_feature = "sse2",
+        any(target_arch = "x86", target_arch = "x86_64"),
+        not(miri)
+    ))] {
+        mod sse2;
+        use sse2 as imp;
+    } else if #[cfg(all(target_arch = "aarch64", target_feature = "neon"))] {
+        mod neon;
+        use neon as imp;
+    } else {
+        mod generic;
+        use generic as imp;
+    }
+}
+
+mod alloc;
+pub(crate) use self::alloc::{do_alloc, Allocator, Global};
+
+mod bitmask;
+
+use self::bitmask::BitMaskIter;
+use self::imp::Group;
+
+// Branch prediction hint. This is currently only available on nightly but it
+// consistently improves performance by 10-15%.
+#[cfg(not(feature = "nightly"))]
+use core::convert::identity as likely;
+#[cfg(not(feature = "nightly"))]
+use core::convert::identity as unlikely;
+#[cfg(feature = "nightly")]
+use core::intrinsics::{likely, unlikely};
+
+// Use strict provenance functions if available.
+#[cfg(feature = "nightly")]
+use core::ptr::invalid_mut;
+// Implement it with a cast otherwise.
+#[cfg(not(feature = "nightly"))]
+#[inline(always)]
+fn invalid_mut<T>(addr: usize) -> *mut T {
+    addr as *mut T
+}
+
+#[inline]
+unsafe fn offset_from<T>(to: *const T, from: *const T) -> usize {
+    to.offset_from(from) as usize
+}
+
+/// Whether memory allocation errors should return an error or abort.
+#[derive(Copy, Clone)]
+enum Fallibility {
+    Fallible,
+    Infallible,
+}
+
+impl Fallibility {
+    /// Error to return on capacity overflow.
+    #[cfg_attr(feature = "inline-more", inline)]
+    fn capacity_overflow(self) -> TryReserveError {
+        match self {
+            Fallibility::Fallible => TryReserveError::CapacityOverflow,
+            Fallibility::Infallible => panic!("Hash table capacity overflow"),
+        }
+    }
+
+    /// Error to return on allocation error.
+    #[cfg_attr(feature = "inline-more", inline)]
+    fn alloc_err(self, layout: Layout) -> TryReserveError {
+        match self {
+            Fallibility::Fallible => TryReserveError::AllocError { layout },
+            Fallibility::Infallible => handle_alloc_error(layout),
+        }
+    }
+}
+
+trait SizedTypeProperties: Sized {
+    const IS_ZERO_SIZED: bool = mem::size_of::<Self>() == 0;
+    const NEEDS_DROP: bool = mem::needs_drop::<Self>();
+}
+
+impl<T> SizedTypeProperties for T {}
+
+/// Control byte value for an empty bucket.
+const EMPTY: u8 = 0b1111_1111;
+
+/// Control byte value for a deleted bucket.
+const DELETED: u8 = 0b1000_0000;
+
+/// Checks whether a control byte represents a full bucket (top bit is clear).
+#[inline]
+fn is_full(ctrl: u8) -> bool {
+    ctrl & 0x80 == 0
+}
+
+/// Checks whether a control byte represents a special value (top bit is set).
+#[inline]
+fn is_special(ctrl: u8) -> bool {
+    ctrl & 0x80 != 0
+}
+
+/// Checks whether a special control value is EMPTY (just check 1 bit).
+#[inline]
+fn special_is_empty(ctrl: u8) -> bool {
+    debug_assert!(is_special(ctrl));
+    ctrl & 0x01 != 0
+}
+
+/// Primary hash function, used to select the initial bucket to probe from.
+#[inline]
+#[allow(clippy::cast_possible_truncation)]
+fn h1(hash: u64) -> usize {
+    // On 32-bit platforms we simply ignore the higher hash bits.
+    hash as usize
+}
+
+// Constant for h2 function that grabing the top 7 bits of the hash.
+const MIN_HASH_LEN: usize = if mem::size_of::<usize>() < mem::size_of::<u64>() {
+    mem::size_of::<usize>()
+} else {
+    mem::size_of::<u64>()
+};
+
+/// Secondary hash function, saved in the low 7 bits of the control byte.
+#[inline]
+#[allow(clippy::cast_possible_truncation)]
+fn h2(hash: u64) -> u8 {
+    // Grab the top 7 bits of the hash. While the hash is normally a full 64-bit
+    // value, some hash functions (such as FxHash) produce a usize result
+    // instead, which means that the top 32 bits are 0 on 32-bit platforms.
+    // So we use MIN_HASH_LEN constant to handle this.
+    let top7 = hash >> (MIN_HASH_LEN * 8 - 7);
+    (top7 & 0x7f) as u8 // truncation
+}
+
+/// Probe sequence based on triangular numbers, which is guaranteed (since our
+/// table size is a power of two) to visit every group of elements exactly once.
+///
+/// A triangular probe has us jump by 1 more group every time. So first we
+/// jump by 1 group (meaning we just continue our linear scan), then 2 groups
+/// (skipping over 1 group), then 3 groups (skipping over 2 groups), and so on.
+///
+/// Proof that the probe will visit every group in the table:
+/// <https://fgiesen.wordpress.com/2015/02/22/triangular-numbers-mod-2n/>
+struct ProbeSeq {
+    pos: usize,
+    stride: usize,
+}
+
+impl ProbeSeq {
+    #[inline]
+    fn move_next(&mut self, bucket_mask: usize) {
+        // We should have found an empty bucket by now and ended the probe.
+        debug_assert!(
+            self.stride <= bucket_mask,
+            "Went past end of probe sequence"
+        );
+
+        self.stride += Group::WIDTH;
+        self.pos += self.stride;
+        self.pos &= bucket_mask;
+    }
+}
+
+/// Returns the number of buckets needed to hold the given number of items,
+/// taking the maximum load factor into account.
+///
+/// Returns `None` if an overflow occurs.
+// Workaround for emscripten bug emscripten-core/emscripten-fastcomp#258
+#[cfg_attr(target_os = "emscripten", inline(never))]
+#[cfg_attr(not(target_os = "emscripten"), inline)]
+fn capacity_to_buckets(cap: usize) -> Option<usize> {
+    debug_assert_ne!(cap, 0);
+
+    // For small tables we require at least 1 empty bucket so that lookups are
+    // guaranteed to terminate if an element doesn't exist in the table.
+    if cap < 8 {
+        // We don't bother with a table size of 2 buckets since that can only
+        // hold a single element. Instead we skip directly to a 4 bucket table
+        // which can hold 3 elements.
+        return Some(if cap < 4 { 4 } else { 8 });
+    }
+
+    // Otherwise require 1/8 buckets to be empty (87.5% load)
+    //
+    // Be careful when modifying this, calculate_layout relies on the
+    // overflow check here.
+    let adjusted_cap = cap.checked_mul(8)? / 7;
+
+    // Any overflows will have been caught by the checked_mul. Also, any
+    // rounding errors from the division above will be cleaned up by
+    // next_power_of_two (which can't overflow because of the previous division).
+    Some(adjusted_cap.next_power_of_two())
+}
+
+/// Returns the maximum effective capacity for the given bucket mask, taking
+/// the maximum load factor into account.
+#[inline]
+fn bucket_mask_to_capacity(bucket_mask: usize) -> usize {
+    if bucket_mask < 8 {
+        // For tables with 1/2/4/8 buckets, we always reserve one empty slot.
+        // Keep in mind that the bucket mask is one less than the bucket count.
+        bucket_mask
+    } else {
+        // For larger tables we reserve 12.5% of the slots as empty.
+        ((bucket_mask + 1) / 8) * 7
+    }
+}
+
+/// Helper which allows the max calculation for ctrl_align to be statically computed for each T
+/// while keeping the rest of `calculate_layout_for` independent of `T`
+#[derive(Copy, Clone)]
+struct TableLayout {
+    size: usize,
+    ctrl_align: usize,
+}
+
+impl TableLayout {
+    #[inline]
+    const fn new<T>() -> Self {
+        let layout = Layout::new::<T>();
+        Self {
+            size: layout.size(),
+            ctrl_align: if layout.align() > Group::WIDTH {
+                layout.align()
+            } else {
+                Group::WIDTH
+            },
+        }
+    }
+
+    #[inline]
+    fn calculate_layout_for(self, buckets: usize) -> Option<(Layout, usize)> {
+        debug_assert!(buckets.is_power_of_two());
+
+        let TableLayout { size, ctrl_align } = self;
+        // Manual layout calculation since Layout methods are not yet stable.
+        let ctrl_offset =
+            size.checked_mul(buckets)?.checked_add(ctrl_align - 1)? & !(ctrl_align - 1);
+        let len = ctrl_offset.checked_add(buckets + Group::WIDTH)?;
+
+        // We need an additional check to ensure that the allocation doesn't
+        // exceed `isize::MAX` (https://github.com/rust-lang/rust/pull/95295).
+        if len > isize::MAX as usize - (ctrl_align - 1) {
+            return None;
+        }
+
+        Some((
+            unsafe { Layout::from_size_align_unchecked(len, ctrl_align) },
+            ctrl_offset,
+        ))
+    }
+}
+
+/// A reference to an empty bucket into which an can be inserted.
+pub struct InsertSlot {
+    index: usize,
+}
+
+/// A reference to a hash table bucket containing a `T`.
+///
+/// This is usually just a pointer to the element itself. However if the element
+/// is a ZST, then we instead track the index of the element in the table so
+/// that `erase` works properly.
+pub struct Bucket<T> {
+    // Actually it is pointer to next element than element itself
+    // this is needed to maintain pointer arithmetic invariants
+    // keeping direct pointer to element introduces difficulty.
+    // Using `NonNull` for variance and niche layout
+    ptr: NonNull<T>,
+}
+
+// This Send impl is needed for rayon support. This is safe since Bucket is
+// never exposed in a public API.
+unsafe impl<T> Send for Bucket<T> {}
+
+impl<T> Clone for Bucket<T> {
+    #[inline]
+    fn clone(&self) -> Self {
+        Self { ptr: self.ptr }
+    }
+}
+
+impl<T> Bucket<T> {
+    /// Creates a [`Bucket`] that contain pointer to the data.
+    /// The pointer calculation is performed by calculating the
+    /// offset from given `base` pointer (convenience for
+    /// `base.as_ptr().sub(index)`).
+    ///
+    /// `index` is in units of `T`; e.g., an `index` of 3 represents a pointer
+    /// offset of `3 * size_of::<T>()` bytes.
+    ///
+    /// If the `T` is a ZST, then we instead track the index of the element
+    /// in the table so that `erase` works properly (return
+    /// `NonNull::new_unchecked((index + 1) as *mut T)`)
+    ///
+    /// # Safety
+    ///
+    /// If `mem::size_of::<T>() != 0`, then the safety rules are directly derived
+    /// from the safety rules for [`<*mut T>::sub`] method of `*mut T` and the safety
+    /// rules of [`NonNull::new_unchecked`] function.
+    ///
+    /// Thus, in order to uphold the safety contracts for the [`<*mut T>::sub`] method
+    /// and [`NonNull::new_unchecked`] function, as well as for the correct
+    /// logic of the work of this crate, the following rules are necessary and
+    /// sufficient:
+    ///
+    /// * the `base` pointer must not be `dangling` and must points to the
+    ///   end of the first `value element` from the `data part` of the table, i.e.
+    ///   must be the pointer that returned by [`RawTable::data_end`] or by
+    ///   [`RawTableInner::data_end<T>`];
+    ///
+    /// * `index` must not be greater than `RawTableInner.bucket_mask`, i.e.
+    ///   `index <= RawTableInner.bucket_mask` or, in other words, `(index + 1)`
+    ///   must be no greater than the number returned by the function
+    ///   [`RawTable::buckets`] or [`RawTableInner::buckets`].
+    ///
+    /// If `mem::size_of::<T>() == 0`, then the only requirement is that the
+    /// `index` must not be greater than `RawTableInner.bucket_mask`, i.e.
+    /// `index <= RawTableInner.bucket_mask` or, in other words, `(index + 1)`
+    /// must be no greater than the number returned by the function
+    /// [`RawTable::buckets`] or [`RawTableInner::buckets`].
+    ///
+    /// [`Bucket`]: crate::raw::Bucket
+    /// [`<*mut T>::sub`]: https://doc.rust-lang.org/core/primitive.pointer.html#method.sub-1
+    /// [`NonNull::new_unchecked`]: https://doc.rust-lang.org/stable/std/ptr/struct.NonNull.html#method.new_unchecked
+    /// [`RawTable::data_end`]: crate::raw::RawTable::data_end
+    /// [`RawTableInner::data_end<T>`]: RawTableInner::data_end<T>
+    /// [`RawTable::buckets`]: crate::raw::RawTable::buckets
+    /// [`RawTableInner::buckets`]: RawTableInner::buckets
+    #[inline]
+    unsafe fn from_base_index(base: NonNull<T>, index: usize) -> Self {
+        // If mem::size_of::<T>() != 0 then return a pointer to an `element` in
+        // the data part of the table (we start counting from "0", so that
+        // in the expression T[last], the "last" index actually one less than the
+        // "buckets" number in the table, i.e. "last = RawTableInner.bucket_mask"):
+        //
+        //                   `from_base_index(base, 1).as_ptr()` returns a pointer that
+        //                   points here in the data part of the table
+        //                   (to the start of T1)
+        //                        |
+        //                        |        `base: NonNull<T>` must point here
+        //                        |         (to the end of T0 or to the start of C0)
+        //                        v         v
+        // [Padding], Tlast, ..., |T1|, T0, |C0, C1, ..., Clast
+        //                           ^
+        //                           `from_base_index(base, 1)` returns a pointer
+        //                           that points here in the data part of the table
+        //                           (to the end of T1)
+        //
+        // where: T0...Tlast - our stored data; C0...Clast - control bytes
+        // or metadata for data.
+        let ptr = if T::IS_ZERO_SIZED {
+            // won't overflow because index must be less than length (bucket_mask)
+            // and bucket_mask is guaranteed to be less than `isize::MAX`
+            // (see TableLayout::calculate_layout_for method)
+            invalid_mut(index + 1)
+        } else {
+            base.as_ptr().sub(index)
+        };
+        Self {
+            ptr: NonNull::new_unchecked(ptr),
+        }
+    }
+
+    /// Calculates the index of a [`Bucket`] as distance between two pointers
+    /// (convenience for `base.as_ptr().offset_from(self.ptr.as_ptr()) as usize`).
+    /// The returned value is in units of T: the distance in bytes divided by
+    /// [`core::mem::size_of::<T>()`].
+    ///
+    /// If the `T` is a ZST, then we return the index of the element in
+    /// the table so that `erase` works properly (return `self.ptr.as_ptr() as usize - 1`).
+    ///
+    /// This function is the inverse of [`from_base_index`].
+    ///
+    /// # Safety
+    ///
+    /// If `mem::size_of::<T>() != 0`, then the safety rules are directly derived
+    /// from the safety rules for [`<*const T>::offset_from`] method of `*const T`.
+    ///
+    /// Thus, in order to uphold the safety contracts for [`<*const T>::offset_from`]
+    /// method, as well as for the correct logic of the work of this crate, the
+    /// following rules are necessary and sufficient:
+    ///
+    /// * `base` contained pointer must not be `dangling` and must point to the
+    ///   end of the first `element` from the `data part` of the table, i.e.
+    ///   must be a pointer that returns by [`RawTable::data_end`] or by
+    ///   [`RawTableInner::data_end<T>`];
+    ///
+    /// * `self` also must not contain dangling pointer;
+    ///
+    /// * both `self` and `base` must be created from the same [`RawTable`]
+    ///   (or [`RawTableInner`]).
+    ///
+    /// If `mem::size_of::<T>() == 0`, this function is always safe.
+    ///
+    /// [`Bucket`]: crate::raw::Bucket
+    /// [`from_base_index`]: crate::raw::Bucket::from_base_index
+    /// [`RawTable::data_end`]: crate::raw::RawTable::data_end
+    /// [`RawTableInner::data_end<T>`]: RawTableInner::data_end<T>
+    /// [`RawTable`]: crate::raw::RawTable
+    /// [`RawTableInner`]: RawTableInner
+    /// [`<*const T>::offset_from`]: https://doc.rust-lang.org/nightly/core/primitive.pointer.html#method.offset_from
+    #[inline]
+    unsafe fn to_base_index(&self, base: NonNull<T>) -> usize {
+        // If mem::size_of::<T>() != 0 then return an index under which we used to store the
+        // `element` in the data part of the table (we start counting from "0", so
+        // that in the expression T[last], the "last" index actually is one less than the
+        // "buckets" number in the table, i.e. "last = RawTableInner.bucket_mask").
+        // For example for 5th element in table calculation is performed like this:
+        //
+        //                        mem::size_of::<T>()
+        //                          |
+        //                          |         `self = from_base_index(base, 5)` that returns pointer
+        //                          |         that points here in tha data part of the table
+        //                          |         (to the end of T5)
+        //                          |           |                    `base: NonNull<T>` must point here
+        //                          v           |                    (to the end of T0 or to the start of C0)
+        //                        /???\         v                      v
+        // [Padding], Tlast, ..., |T10|, ..., T5|, T4, T3, T2, T1, T0, |C0, C1, C2, C3, C4, C5, ..., C10, ..., Clast
+        //                                      \__________  __________/
+        //                                                 \/
+        //                                     `bucket.to_base_index(base)` = 5
+        //                                     (base.as_ptr() as usize - self.ptr.as_ptr() as usize) / mem::size_of::<T>()
+        //
+        // where: T0...Tlast - our stored data; C0...Clast - control bytes or metadata for data.
+        if T::IS_ZERO_SIZED {
+            // this can not be UB
+            self.ptr.as_ptr() as usize - 1
+        } else {
+            offset_from(base.as_ptr(), self.ptr.as_ptr())
+        }
+    }
+
+    /// Acquires the underlying raw pointer `*mut T` to `data`.
+    ///
+    /// # Note
+    ///
+    /// If `T` is not [`Copy`], do not use `*mut T` methods that can cause calling the
+    /// destructor of `T` (for example the [`<*mut T>::drop_in_place`] method), because
+    /// for properly dropping the data we also need to clear `data` control bytes. If we
+    /// drop data, but do not clear `data control byte` it leads to double drop when
+    /// [`RawTable`] goes out of scope.
+    ///
+    /// If you modify an already initialized `value`, so [`Hash`] and [`Eq`] on the new
+    /// `T` value and its borrowed form *must* match those for the old `T` value, as the map
+    /// will not re-evaluate where the new value should go, meaning the value may become
+    /// "lost" if their location does not reflect their state.
+    ///
+    /// [`RawTable`]: crate::raw::RawTable
+    /// [`<*mut T>::drop_in_place`]: https://doc.rust-lang.org/core/primitive.pointer.html#method.drop_in_place
+    /// [`Hash`]: https://doc.rust-lang.org/core/hash/trait.Hash.html
+    /// [`Eq`]: https://doc.rust-lang.org/core/cmp/trait.Eq.html
+    ///
+    /// # Examples
+    ///
+    /// ```
+    /// # #[cfg(feature = "raw")]
+    /// # fn test() {
+    /// use core::hash::{BuildHasher, Hash};
+    /// use hashbrown::raw::{Bucket, RawTable};
+    ///
+    /// type NewHashBuilder = core::hash::BuildHasherDefault<ahash::AHasher>;
+    ///
+    /// fn make_hash<K: Hash + ?Sized, S: BuildHasher>(hash_builder: &S, key: &K) -> u64 {
+    ///     use core::hash::Hasher;
+    ///     let mut state = hash_builder.build_hasher();
+    ///     key.hash(&mut state);
+    ///     state.finish()
+    /// }
+    ///
+    /// let hash_builder = NewHashBuilder::default();
+    /// let mut table = RawTable::new();
+    ///
+    /// let value = ("a", 100);
+    /// let hash = make_hash(&hash_builder, &value.0);
+    ///
+    /// table.insert(hash, value.clone(), |val| make_hash(&hash_builder, &val.0));
+    ///
+    /// let bucket: Bucket<(&str, i32)> = table.find(hash, |(k1, _)| k1 == &value.0).unwrap();
+    ///
+    /// assert_eq!(unsafe { &*bucket.as_ptr() }, &("a", 100));
+    /// # }
+    /// # fn main() {
+    /// #     #[cfg(feature = "raw")]
+    /// #     test()
+    /// # }
+    /// ```
+    #[inline]
+    pub fn as_ptr(&self) -> *mut T {
+        if T::IS_ZERO_SIZED {
+            // Just return an arbitrary ZST pointer which is properly aligned
+            // invalid pointer is good enough for ZST
+            invalid_mut(mem::align_of::<T>())
+        } else {
+            unsafe { self.ptr.as_ptr().sub(1) }
+        }
+    }
+
+    /// Create a new [`Bucket`] that is offset from the `self` by the given
+    /// `offset`. The pointer calculation is performed by calculating the
+    /// offset from `self` pointer (convenience for `self.ptr.as_ptr().sub(offset)`).
+    /// This function is used for iterators.
+    ///
+    /// `offset` is in units of `T`; e.g., a `offset` of 3 represents a pointer
+    /// offset of `3 * size_of::<T>()` bytes.
+    ///
+    /// # Safety
+    ///
+    /// If `mem::size_of::<T>() != 0`, then the safety rules are directly derived
+    /// from the safety rules for [`<*mut T>::sub`] method of `*mut T` and safety
+    /// rules of [`NonNull::new_unchecked`] function.
+    ///
+    /// Thus, in order to uphold the safety contracts for [`<*mut T>::sub`] method
+    /// and [`NonNull::new_unchecked`] function, as well as for the correct
+    /// logic of the work of this crate, the following rules are necessary and
+    /// sufficient:
+    ///
+    /// * `self` contained pointer must not be `dangling`;
+    ///
+    /// * `self.to_base_index() + ofset` must not be greater than `RawTableInner.bucket_mask`,
+    ///   i.e. `(self.to_base_index() + ofset) <= RawTableInner.bucket_mask` or, in other
+    ///   words, `self.to_base_index() + ofset + 1` must be no greater than the number returned
+    ///   by the function [`RawTable::buckets`] or [`RawTableInner::buckets`].
+    ///
+    /// If `mem::size_of::<T>() == 0`, then the only requirement is that the
+    /// `self.to_base_index() + ofset` must not be greater than `RawTableInner.bucket_mask`,
+    /// i.e. `(self.to_base_index() + ofset) <= RawTableInner.bucket_mask` or, in other words,
+    /// `self.to_base_index() + ofset + 1` must be no greater than the number returned by the
+    /// function [`RawTable::buckets`] or [`RawTableInner::buckets`].
+    ///
+    /// [`Bucket`]: crate::raw::Bucket
+    /// [`<*mut T>::sub`]: https://doc.rust-lang.org/core/primitive.pointer.html#method.sub-1
+    /// [`NonNull::new_unchecked`]: https://doc.rust-lang.org/stable/std/ptr/struct.NonNull.html#method.new_unchecked
+    /// [`RawTable::buckets`]: crate::raw::RawTable::buckets
+    /// [`RawTableInner::buckets`]: RawTableInner::buckets
+    #[inline]
+    unsafe fn next_n(&self, offset: usize) -> Self {
+        let ptr = if T::IS_ZERO_SIZED {
+            // invalid pointer is good enough for ZST
+            invalid_mut(self.ptr.as_ptr() as usize + offset)
+        } else {
+            self.ptr.as_ptr().sub(offset)
+        };
+        Self {
+            ptr: NonNull::new_unchecked(ptr),
+        }
+    }
+
+    /// Executes the destructor (if any) of the pointed-to `data`.
+    ///
+    /// # Safety
+    ///
+    /// See [`ptr::drop_in_place`] for safety concerns.
+    ///
+    /// You should use [`RawTable::erase`] instead of this function,
+    /// or be careful with calling this function directly, because for
+    /// properly dropping the data we need also clear `data` control bytes.
+    /// If we drop data, but do not erase `data control byte` it leads to
+    /// double drop when [`RawTable`] goes out of scope.
+    ///
+    /// [`ptr::drop_in_place`]: https://doc.rust-lang.org/core/ptr/fn.drop_in_place.html
+    /// [`RawTable`]: crate::raw::RawTable
+    /// [`RawTable::erase`]: crate::raw::RawTable::erase
+    #[cfg_attr(feature = "inline-more", inline)]
+    pub(crate) unsafe fn drop(&self) {
+        self.as_ptr().drop_in_place();
+    }
+
+    /// Reads the `value` from `self` without moving it. This leaves the
+    /// memory in `self` unchanged.
+    ///
+    /// # Safety
+    ///
+    /// See [`ptr::read`] for safety concerns.
+    ///
+    /// You should use [`RawTable::remove`] instead of this function,
+    /// or be careful with calling this function directly, because compiler
+    /// calls its destructor when readed `value` goes out of scope. It
+    /// can cause double dropping when [`RawTable`] goes out of scope,
+    /// because of not erased `data control byte`.
+    ///
+    /// [`ptr::read`]: https://doc.rust-lang.org/core/ptr/fn.read.html
+    /// [`RawTable`]: crate::raw::RawTable
+    /// [`RawTable::remove`]: crate::raw::RawTable::remove
+    #[inline]
+    pub(crate) unsafe fn read(&self) -> T {
+        self.as_ptr().read()
+    }
+
+    /// Overwrites a memory location with the given `value` without reading
+    /// or dropping the old value (like [`ptr::write`] function).
+    ///
+    /// # Safety
+    ///
+    /// See [`ptr::write`] for safety concerns.
+    ///
+    /// # Note
+    ///
+    /// [`Hash`] and [`Eq`] on the new `T` value and its borrowed form *must* match
+    /// those for the old `T` value, as the map will not re-evaluate where the new
+    /// value should go, meaning the value may become "lost" if their location
+    /// does not reflect their state.
+    ///
+    /// [`ptr::write`]: https://doc.rust-lang.org/core/ptr/fn.write.html
+    /// [`Hash`]: https://doc.rust-lang.org/core/hash/trait.Hash.html
+    /// [`Eq`]: https://doc.rust-lang.org/core/cmp/trait.Eq.html
+    #[inline]
+    pub(crate) unsafe fn write(&self, val: T) {
+        self.as_ptr().write(val);
+    }
+
+    /// Returns a shared immutable reference to the `value`.
+    ///
+    /// # Safety
+    ///
+    /// See [`NonNull::as_ref`] for safety concerns.
+    ///
+    /// [`NonNull::as_ref`]: https://doc.rust-lang.org/core/ptr/struct.NonNull.html#method.as_ref
+    ///
+    /// # Examples
+    ///
+    /// ```
+    /// # #[cfg(feature = "raw")]
+    /// # fn test() {
+    /// use core::hash::{BuildHasher, Hash};
+    /// use hashbrown::raw::{Bucket, RawTable};
+    ///
+    /// type NewHashBuilder = core::hash::BuildHasherDefault<ahash::AHasher>;
+    ///
+    /// fn make_hash<K: Hash + ?Sized, S: BuildHasher>(hash_builder: &S, key: &K) -> u64 {
+    ///     use core::hash::Hasher;
+    ///     let mut state = hash_builder.build_hasher();
+    ///     key.hash(&mut state);
+    ///     state.finish()
+    /// }
+    ///
+    /// let hash_builder = NewHashBuilder::default();
+    /// let mut table = RawTable::new();
+    ///
+    /// let value: (&str, String) = ("A pony", "is a small horse".to_owned());
+    /// let hash = make_hash(&hash_builder, &value.0);
+    ///
+    /// table.insert(hash, value.clone(), |val| make_hash(&hash_builder, &val.0));
+    ///
+    /// let bucket: Bucket<(&str, String)> = table.find(hash, |(k, _)| k == &value.0).unwrap();
+    ///
+    /// assert_eq!(
+    ///     unsafe { bucket.as_ref() },
+    ///     &("A pony", "is a small horse".to_owned())
+    /// );
+    /// # }
+    /// # fn main() {
+    /// #     #[cfg(feature = "raw")]
+    /// #     test()
+    /// # }
+    /// ```
+    #[inline]
+    pub unsafe fn as_ref<'a>(&self) -> &'a T {
+        &*self.as_ptr()
+    }
+
+    /// Returns a unique mutable reference to the `value`.
+    ///
+    /// # Safety
+    ///
+    /// See [`NonNull::as_mut`] for safety concerns.
+    ///
+    /// # Note
+    ///
+    /// [`Hash`] and [`Eq`] on the new `T` value and its borrowed form *must* match
+    /// those for the old `T` value, as the map will not re-evaluate where the new
+    /// value should go, meaning the value may become "lost" if their location
+    /// does not reflect their state.
+    ///
+    /// [`NonNull::as_mut`]: https://doc.rust-lang.org/core/ptr/struct.NonNull.html#method.as_mut
+    /// [`Hash`]: https://doc.rust-lang.org/core/hash/trait.Hash.html
+    /// [`Eq`]: https://doc.rust-lang.org/core/cmp/trait.Eq.html
+    ///
+    /// # Examples
+    ///
+    /// ```
+    /// # #[cfg(feature = "raw")]
+    /// # fn test() {
+    /// use core::hash::{BuildHasher, Hash};
+    /// use hashbrown::raw::{Bucket, RawTable};
+    ///
+    /// type NewHashBuilder = core::hash::BuildHasherDefault<ahash::AHasher>;
+    ///
+    /// fn make_hash<K: Hash + ?Sized, S: BuildHasher>(hash_builder: &S, key: &K) -> u64 {
+    ///     use core::hash::Hasher;
+    ///     let mut state = hash_builder.build_hasher();
+    ///     key.hash(&mut state);
+    ///     state.finish()
+    /// }
+    ///
+    /// let hash_builder = NewHashBuilder::default();
+    /// let mut table = RawTable::new();
+    ///
+    /// let value: (&str, String) = ("A pony", "is a small horse".to_owned());
+    /// let hash = make_hash(&hash_builder, &value.0);
+    ///
+    /// table.insert(hash, value.clone(), |val| make_hash(&hash_builder, &val.0));
+    ///
+    /// let bucket: Bucket<(&str, String)> = table.find(hash, |(k, _)| k == &value.0).unwrap();
+    ///
+    /// unsafe {
+    ///     bucket
+    ///         .as_mut()
+    ///         .1
+    ///         .push_str(" less than 147 cm at the withers")
+    /// };
+    /// assert_eq!(
+    ///     unsafe { bucket.as_ref() },
+    ///     &(
+    ///         "A pony",
+    ///         "is a small horse less than 147 cm at the withers".to_owned()
+    ///     )
+    /// );
+    /// # }
+    /// # fn main() {
+    /// #     #[cfg(feature = "raw")]
+    /// #     test()
+    /// # }
+    /// ```
+    #[inline]
+    pub unsafe fn as_mut<'a>(&self) -> &'a mut T {
+        &mut *self.as_ptr()
+    }
+
+    /// Copies `size_of<T>` bytes from `other` to `self`. The source
+    /// and destination may *not* overlap.
+    ///
+    /// # Safety
+    ///
+    /// See [`ptr::copy_nonoverlapping`] for safety concerns.
+    ///
+    /// Like [`read`], `copy_nonoverlapping` creates a bitwise copy of `T`, regardless of
+    /// whether `T` is [`Copy`]. If `T` is not [`Copy`], using *both* the values
+    /// in the region beginning at `*self` and the region beginning at `*other` can
+    /// [violate memory safety].
+    ///
+    /// # Note
+    ///
+    /// [`Hash`] and [`Eq`] on the new `T` value and its borrowed form *must* match
+    /// those for the old `T` value, as the map will not re-evaluate where the new
+    /// value should go, meaning the value may become "lost" if their location
+    /// does not reflect their state.
+    ///
+    /// [`ptr::copy_nonoverlapping`]: https://doc.rust-lang.org/core/ptr/fn.copy_nonoverlapping.html
+    /// [`read`]: https://doc.rust-lang.org/core/ptr/fn.read.html
+    /// [violate memory safety]: https://doc.rust-lang.org/std/ptr/fn.read.html#ownership-of-the-returned-value
+    /// [`Hash`]: https://doc.rust-lang.org/core/hash/trait.Hash.html
+    /// [`Eq`]: https://doc.rust-lang.org/core/cmp/trait.Eq.html
+    #[cfg(feature = "raw")]
+    #[inline]
+    pub unsafe fn copy_from_nonoverlapping(&self, other: &Self) {
+        self.as_ptr().copy_from_nonoverlapping(other.as_ptr(), 1);
+    }
+}
+
+/// A raw hash table with an unsafe API.
+pub struct RawTable<T, A: Allocator = Global> {
+    table: RawTableInner,
+    alloc: A,
+    // Tell dropck that we own instances of T.
+    marker: PhantomData<T>,
+}
+
+/// Non-generic part of `RawTable` which allows functions to be instantiated only once regardless
+/// of how many different key-value types are used.
+struct RawTableInner {
+    // Mask to get an index from a hash value. The value is one less than the
+    // number of buckets in the table.
+    bucket_mask: usize,
+
+    // [Padding], T1, T2, ..., Tlast, C1, C2, ...
+    //                                ^ points here
+    ctrl: NonNull<u8>,
+
+    // Number of elements that can be inserted before we need to grow the table
+    growth_left: usize,
+
+    // Number of elements in the table, only really used by len()
+    items: usize,
+}
+
+impl<T> RawTable<T, Global> {
+    /// Creates a new empty hash table without allocating any memory.
+    ///
+    /// In effect this returns a table with exactly 1 bucket. However we can
+    /// leave the data pointer dangling since that bucket is never written to
+    /// due to our load factor forcing us to always have at least 1 free bucket.
+    #[inline]
+    pub const fn new() -> Self {
+        Self {
+            table: RawTableInner::NEW,
+            alloc: Global,
+            marker: PhantomData,
+        }
+    }
+
+    /// Attempts to allocate a new hash table with at least enough capacity
+    /// for inserting the given number of elements without reallocating.
+    #[cfg(feature = "raw")]
+    pub fn try_with_capacity(capacity: usize) -> Result<Self, TryReserveError> {
+        Self::try_with_capacity_in(capacity, Global)
+    }
+
+    /// Allocates a new hash table with at least enough capacity for inserting
+    /// the given number of elements without reallocating.
+    pub fn with_capacity(capacity: usize) -> Self {
+        Self::with_capacity_in(capacity, Global)
+    }
+}
+
+impl<T, A: Allocator> RawTable<T, A> {
+    const TABLE_LAYOUT: TableLayout = TableLayout::new::<T>();
+
+    /// Creates a new empty hash table without allocating any memory, using the
+    /// given allocator.
+    ///
+    /// In effect this returns a table with exactly 1 bucket. However we can
+    /// leave the data pointer dangling since that bucket is never written to
+    /// due to our load factor forcing us to always have at least 1 free bucket.
+    #[inline]
+    pub const fn new_in(alloc: A) -> Self {
+        Self {
+            table: RawTableInner::NEW,
+            alloc,
+            marker: PhantomData,
+        }
+    }
+
+    /// Allocates a new hash table with the given number of buckets.
+    ///
+    /// The control bytes are left uninitialized.
+    #[cfg_attr(feature = "inline-more", inline)]
+    unsafe fn new_uninitialized(
+        alloc: A,
+        buckets: usize,
+        fallibility: Fallibility,
+    ) -> Result<Self, TryReserveError> {
+        debug_assert!(buckets.is_power_of_two());
+
+        Ok(Self {
+            table: RawTableInner::new_uninitialized(
+                &alloc,
+                Self::TABLE_LAYOUT,
+                buckets,
+                fallibility,
+            )?,
+            alloc,
+            marker: PhantomData,
+        })
+    }
+
+    /// Attempts to allocate a new hash table using the given allocator, with at least enough
+    /// capacity for inserting the given number of elements without reallocating.
+    #[cfg(feature = "raw")]
+    pub fn try_with_capacity_in(capacity: usize, alloc: A) -> Result<Self, TryReserveError> {
+        Ok(Self {
+            table: RawTableInner::fallible_with_capacity(
+                &alloc,
+                Self::TABLE_LAYOUT,
+                capacity,
+                Fallibility::Fallible,
+            )?,
+            alloc,
+            marker: PhantomData,
+        })
+    }
+
+    /// Allocates a new hash table using the given allocator, with at least enough capacity for
+    /// inserting the given number of elements without reallocating.
+    pub fn with_capacity_in(capacity: usize, alloc: A) -> Self {
+        Self {
+            table: RawTableInner::with_capacity(&alloc, Self::TABLE_LAYOUT, capacity),
+            alloc,
+            marker: PhantomData,
+        }
+    }
+
+    /// Returns a reference to the underlying allocator.
+    #[inline]
+    pub fn allocator(&self) -> &A {
+        &self.alloc
+    }
+
+    /// Returns pointer to one past last element of data table.
+    #[inline]
+    pub unsafe fn data_end(&self) -> NonNull<T> {
+        NonNull::new_unchecked(self.table.ctrl.as_ptr().cast())
+    }
+
+    /// Returns pointer to start of data table.
+    #[inline]
+    #[cfg(any(feature = "raw", feature = "nightly"))]
+    pub unsafe fn data_start(&self) -> NonNull<T> {
+        NonNull::new_unchecked(self.data_end().as_ptr().wrapping_sub(self.buckets()))
+    }
+
+    /// Return the information about memory allocated by the table.
+    ///
+    /// `RawTable` allocates single memory block to store both data and metadata.
+    /// This function returns allocation size and alignment and the beginning of the area.
+    /// These are the arguments which will be passed to `dealloc` when the table is dropped.
+    ///
+    /// This function might be useful for memory profiling.
+    #[inline]
+    #[cfg(feature = "raw")]
+    pub fn allocation_info(&self) -> (NonNull<u8>, Layout) {
+        // SAFETY: We use the same `table_layout` that was used to allocate
+        // this table.
+        unsafe { self.table.allocation_info_or_zero(Self::TABLE_LAYOUT) }
+    }
+
+    /// Returns the index of a bucket from a `Bucket`.
+    #[inline]
+    pub unsafe fn bucket_index(&self, bucket: &Bucket<T>) -> usize {
+        bucket.to_base_index(self.data_end())
+    }
+
+    /// Returns a pointer to an element in the table.
+    #[inline]
+    pub unsafe fn bucket(&self, index: usize) -> Bucket<T> {
+        debug_assert_ne!(self.table.bucket_mask, 0);
+        debug_assert!(index < self.buckets());
+        Bucket::from_base_index(self.data_end(), index)
+    }
+
+    /// Erases an element from the table without dropping it.
+    #[cfg_attr(feature = "inline-more", inline)]
+    unsafe fn erase_no_drop(&mut self, item: &Bucket<T>) {
+        let index = self.bucket_index(item);
+        self.table.erase(index);
+    }
+
+    /// Erases an element from the table, dropping it in place.
+    #[cfg_attr(feature = "inline-more", inline)]
+    #[allow(clippy::needless_pass_by_value)]
+    pub unsafe fn erase(&mut self, item: Bucket<T>) {
+        // Erase the element from the table first since drop might panic.
+        self.erase_no_drop(&item);
+        item.drop();
+    }
+
+    /// Finds and erases an element from the table, dropping it in place.
+    /// Returns true if an element was found.
+    #[cfg(feature = "raw")]
+    #[cfg_attr(feature = "inline-more", inline)]
+    pub fn erase_entry(&mut self, hash: u64, eq: impl FnMut(&T) -> bool) -> bool {
+        // Avoid `Option::map` because it bloats LLVM IR.
+        if let Some(bucket) = self.find(hash, eq) {
+            unsafe {
+                self.erase(bucket);
+            }
+            true
+        } else {
+            false
+        }
+    }
+
+    /// Removes an element from the table, returning it.
+    ///
+    /// This also returns an `InsertSlot` pointing to the newly free bucket.
+    #[cfg_attr(feature = "inline-more", inline)]
+    #[allow(clippy::needless_pass_by_value)]
+    pub unsafe fn remove(&mut self, item: Bucket<T>) -> (T, InsertSlot) {
+        self.erase_no_drop(&item);
+        (
+            item.read(),
+            InsertSlot {
+                index: self.bucket_index(&item),
+            },
+        )
+    }
+
+    /// Finds and removes an element from the table, returning it.
+    #[cfg_attr(feature = "inline-more", inline)]
+    pub fn remove_entry(&mut self, hash: u64, eq: impl FnMut(&T) -> bool) -> Option<T> {
+        // Avoid `Option::map` because it bloats LLVM IR.
+        match self.find(hash, eq) {
+            Some(bucket) => Some(unsafe { self.remove(bucket).0 }),
+            None => None,
+        }
+    }
+
+    /// Marks all table buckets as empty without dropping their contents.
+    #[cfg_attr(feature = "inline-more", inline)]
+    pub fn clear_no_drop(&mut self) {
+        self.table.clear_no_drop();
+    }
+
+    /// Removes all elements from the table without freeing the backing memory.
+    #[cfg_attr(feature = "inline-more", inline)]
+    pub fn clear(&mut self) {
+        if self.is_empty() {
+            // Special case empty table to avoid surprising O(capacity) time.
+            return;
+        }
+        // Ensure that the table is reset even if one of the drops panic
+        let mut self_ = guard(self, |self_| self_.clear_no_drop());
+        unsafe {
+            // SAFETY: ScopeGuard sets to zero the `items` field of the table
+            // even in case of panic during the dropping of the elements so
+            // that there will be no double drop of the elements.
+            self_.table.drop_elements::<T>();
+        }
+    }
+
+    /// Shrinks the table to fit `max(self.len(), min_size)` elements.
+    #[cfg_attr(feature = "inline-more", inline)]
+    pub fn shrink_to(&mut self, min_size: usize, hasher: impl Fn(&T) -> u64) {
+        // Calculate the minimal number of elements that we need to reserve
+        // space for.
+        let min_size = usize::max(self.table.items, min_size);
+        if min_size == 0 {
+            let mut old_inner = mem::replace(&mut self.table, RawTableInner::NEW);
+            unsafe {
+                // SAFETY:
+                // 1. We call the function only once;
+                // 2. We know for sure that `alloc` and `table_layout` matches the [`Allocator`]
+                //    and [`TableLayout`] that were used to allocate this table.
+                // 3. If any elements' drop function panics, then there will only be a memory leak,
+                //    because we have replaced the inner table with a new one.
+                old_inner.drop_inner_table::<T, _>(&self.alloc, Self::TABLE_LAYOUT);
+            }
+            return;
+        }
+
+        // Calculate the number of buckets that we need for this number of
+        // elements. If the calculation overflows then the requested bucket
+        // count must be larger than what we have right and nothing needs to be
+        // done.
+        let min_buckets = match capacity_to_buckets(min_size) {
+            Some(buckets) => buckets,
+            None => return,
+        };
+
+        // If we have more buckets than we need, shrink the table.
+        if min_buckets < self.buckets() {
+            // Fast path if the table is empty
+            if self.table.items == 0 {
+                let new_inner =
+                    RawTableInner::with_capacity(&self.alloc, Self::TABLE_LAYOUT, min_size);
+                let mut old_inner = mem::replace(&mut self.table, new_inner);
+                unsafe {
+                    // SAFETY:
+                    // 1. We call the function only once;
+                    // 2. We know for sure that `alloc` and `table_layout` matches the [`Allocator`]
+                    //    and [`TableLayout`] that were used to allocate this table.
+                    // 3. If any elements' drop function panics, then there will only be a memory leak,
+                    //    because we have replaced the inner table with a new one.
+                    old_inner.drop_inner_table::<T, _>(&self.alloc, Self::TABLE_LAYOUT);
+                }
+            } else {
+                // Avoid `Result::unwrap_or_else` because it bloats LLVM IR.
+                unsafe {
+                    // SAFETY:
+                    // 1. We know for sure that `min_size >= self.table.items`.
+                    // 2. The [`RawTableInner`] must already have properly initialized control bytes since
+                    //    we will never expose RawTable::new_uninitialized in a public API.
+                    if self
+                        .resize(min_size, hasher, Fallibility::Infallible)
+                        .is_err()
+                    {
+                        // SAFETY: The result of calling the `resize` function cannot be an error
+                        // because `fallibility == Fallibility::Infallible.
+                        hint::unreachable_unchecked()
+                    }
+                }
+            }
+        }
+    }
+
+    /// Ensures that at least `additional` items can be inserted into the table
+    /// without reallocation.
+    #[cfg_attr(feature = "inline-more", inline)]
+    pub fn reserve(&mut self, additional: usize, hasher: impl Fn(&T) -> u64) {
+        if unlikely(additional > self.table.growth_left) {
+            // Avoid `Result::unwrap_or_else` because it bloats LLVM IR.
+            unsafe {
+                // SAFETY: The [`RawTableInner`] must already have properly initialized control
+                // bytes since we will never expose RawTable::new_uninitialized in a public API.
+                if self
+                    .reserve_rehash(additional, hasher, Fallibility::Infallible)
+                    .is_err()
+                {
+                    // SAFETY: All allocation errors will be caught inside `RawTableInner::reserve_rehash`.
+                    hint::unreachable_unchecked()
+                }
+            }
+        }
+    }
+
+    /// Tries to ensure that at least `additional` items can be inserted into
+    /// the table without reallocation.
+    #[cfg_attr(feature = "inline-more", inline)]
+    pub fn try_reserve(
+        &mut self,
+        additional: usize,
+        hasher: impl Fn(&T) -> u64,
+    ) -> Result<(), TryReserveError> {
+        if additional > self.table.growth_left {
+            // SAFETY: The [`RawTableInner`] must already have properly initialized control
+            // bytes since we will never expose RawTable::new_uninitialized in a public API.
+            unsafe { self.reserve_rehash(additional, hasher, Fallibility::Fallible) }
+        } else {
+            Ok(())
+        }
+    }
+
+    /// Out-of-line slow path for `reserve` and `try_reserve`.
+    ///
+    /// # Safety
+    ///
+    /// The [`RawTableInner`] must have properly initialized control bytes,
+    /// otherwise calling this function results in [`undefined behavior`]
+    ///
+    /// [`undefined behavior`]: https://doc.rust-lang.org/reference/behavior-considered-undefined.html
+    #[cold]
+    #[inline(never)]
+    unsafe fn reserve_rehash(
+        &mut self,
+        additional: usize,
+        hasher: impl Fn(&T) -> u64,
+        fallibility: Fallibility,
+    ) -> Result<(), TryReserveError> {
+        unsafe {
+            // SAFETY:
+            // 1. We know for sure that `alloc` and `layout` matches the [`Allocator`] and
+            //    [`TableLayout`] that were used to allocate this table.
+            // 2. The `drop` function is the actual drop function of the elements stored in
+            //    the table.
+            // 3. The caller ensures that the control bytes of the `RawTableInner`
+            //    are already initialized.
+            self.table.reserve_rehash_inner(
+                &self.alloc,
+                additional,
+                &|table, index| hasher(table.bucket::<T>(index).as_ref()),
+                fallibility,
+                Self::TABLE_LAYOUT,
+                if T::NEEDS_DROP {
+                    Some(mem::transmute(ptr::drop_in_place::<T> as unsafe fn(*mut T)))
+                } else {
+                    None
+                },
+            )
+        }
+    }
+
+    /// Allocates a new table of a different size and moves the contents of the
+    /// current table into it.
+    ///
+    /// # Safety
+    ///
+    /// The [`RawTableInner`] must have properly initialized control bytes,
+    /// otherwise calling this function results in [`undefined behavior`]
+    ///
+    /// The caller of this function must ensure that `capacity >= self.table.items`
+    /// otherwise:
+    ///
+    /// * If `self.table.items != 0`, calling of this function with `capacity`
+    ///   equal to 0 (`capacity == 0`) results in [`undefined behavior`].
+    ///
+    /// * If `capacity_to_buckets(capacity) < Group::WIDTH` and
+    ///   `self.table.items > capacity_to_buckets(capacity)`
+    ///   calling this function results in [`undefined behavior`].
+    ///
+    /// * If `capacity_to_buckets(capacity) >= Group::WIDTH` and
+    ///   `self.table.items > capacity_to_buckets(capacity)`
+    ///   calling this function are never return (will go into an
+    ///   infinite loop).
+    ///
+    /// See [`RawTableInner::find_insert_slot`] for more information.
+    ///
+    /// [`RawTableInner::find_insert_slot`]: RawTableInner::find_insert_slot
+    /// [`undefined behavior`]: https://doc.rust-lang.org/reference/behavior-considered-undefined.html
+    unsafe fn resize(
+        &mut self,
+        capacity: usize,
+        hasher: impl Fn(&T) -> u64,
+        fallibility: Fallibility,
+    ) -> Result<(), TryReserveError> {
+        // SAFETY:
+        // 1. The caller of this function guarantees that `capacity >= self.table.items`.
+        // 2. We know for sure that `alloc` and `layout` matches the [`Allocator`] and
+        //    [`TableLayout`] that were used to allocate this table.
+        // 3. The caller ensures that the control bytes of the `RawTableInner`
+        //    are already initialized.
+        self.table.resize_inner(
+            &self.alloc,
+            capacity,
+            &|table, index| hasher(table.bucket::<T>(index).as_ref()),
+            fallibility,
+            Self::TABLE_LAYOUT,
+        )
+    }
+
+    /// Inserts a new element into the table, and returns its raw bucket.
+    ///
+    /// This does not check if the given element already exists in the table.
+    #[cfg_attr(feature = "inline-more", inline)]
+    pub fn insert(&mut self, hash: u64, value: T, hasher: impl Fn(&T) -> u64) -> Bucket<T> {
+        unsafe {
+            // SAFETY:
+            // 1. The [`RawTableInner`] must already have properly initialized control bytes since
+            //    we will never expose `RawTable::new_uninitialized` in a public API.
+            //
+            // 2. We reserve additional space (if necessary) right after calling this function.
+            let mut slot = self.table.find_insert_slot(hash);
+
+            // We can avoid growing the table once we have reached our load factor if we are replacing
+            // a tombstone. This works since the number of EMPTY slots does not change in this case.
+            //
+            // SAFETY: The function is guaranteed to return [`InsertSlot`] that contains an index
+            // in the range `0..=self.buckets()`.
+            let old_ctrl = *self.table.ctrl(slot.index);
+            if unlikely(self.table.growth_left == 0 && special_is_empty(old_ctrl)) {
+                self.reserve(1, hasher);
+                // SAFETY: We know for sure that `RawTableInner` has control bytes
+                // initialized and that there is extra space in the table.
+                slot = self.table.find_insert_slot(hash);
+            }
+
+            self.insert_in_slot(hash, slot, value)
+        }
+    }
+
+    /// Attempts to insert a new element without growing the table and return its raw bucket.
+    ///
+    /// Returns an `Err` containing the given element if inserting it would require growing the
+    /// table.
+    ///
+    /// This does not check if the given element already exists in the table.
+    #[cfg(feature = "raw")]
+    #[cfg_attr(feature = "inline-more", inline)]
+    pub fn try_insert_no_grow(&mut self, hash: u64, value: T) -> Result<Bucket<T>, T> {
+        unsafe {
+            match self.table.prepare_insert_no_grow(hash) {
+                Ok(index) => {
+                    let bucket = self.bucket(index);
+                    bucket.write(value);
+                    Ok(bucket)
+                }
+                Err(()) => Err(value),
+            }
+        }
+    }
+
+    /// Inserts a new element into the table, and returns a mutable reference to it.
+    ///
+    /// This does not check if the given element already exists in the table.
+    #[cfg_attr(feature = "inline-more", inline)]
+    pub fn insert_entry(&mut self, hash: u64, value: T, hasher: impl Fn(&T) -> u64) -> &mut T {
+        unsafe { self.insert(hash, value, hasher).as_mut() }
+    }
+
+    /// Inserts a new element into the table, without growing the table.
+    ///
+    /// There must be enough space in the table to insert the new element.
+    ///
+    /// This does not check if the given element already exists in the table.
+    #[cfg_attr(feature = "inline-more", inline)]
+    #[cfg(any(feature = "raw", feature = "rustc-internal-api"))]
+    pub unsafe fn insert_no_grow(&mut self, hash: u64, value: T) -> Bucket<T> {
+        let (index, old_ctrl) = self.table.prepare_insert_slot(hash);
+        let bucket = self.table.bucket(index);
+
+        // If we are replacing a DELETED entry then we don't need to update
+        // the load counter.
+        self.table.growth_left -= special_is_empty(old_ctrl) as usize;
+
+        bucket.write(value);
+        self.table.items += 1;
+        bucket
+    }
+
+    /// Temporary removes a bucket, applying the given function to the removed
+    /// element and optionally put back the returned value in the same bucket.
+    ///
+    /// Returns `true` if the bucket still contains an element
+    ///
+    /// This does not check if the given bucket is actually occupied.
+    #[cfg_attr(feature = "inline-more", inline)]
+    pub unsafe fn replace_bucket_with<F>(&mut self, bucket: Bucket<T>, f: F) -> bool
+    where
+        F: FnOnce(T) -> Option<T>,
+    {
+        let index = self.bucket_index(&bucket);
+        let old_ctrl = *self.table.ctrl(index);
+        debug_assert!(self.is_bucket_full(index));
+        let old_growth_left = self.table.growth_left;
+        let item = self.remove(bucket).0;
+        if let Some(new_item) = f(item) {
+            self.table.growth_left = old_growth_left;
+            self.table.set_ctrl(index, old_ctrl);
+            self.table.items += 1;
+            self.bucket(index).write(new_item);
+            true
+        } else {
+            false
+        }
+    }
+
+    /// Searches for an element in the table. If the element is not found,
+    /// returns `Err` with the position of a slot where an element with the
+    /// same hash could be inserted.
+    ///
+    /// This function may resize the table if additional space is required for
+    /// inserting an element.
+    #[inline]
+    pub fn find_or_find_insert_slot(
+        &mut self,
+        hash: u64,
+        mut eq: impl FnMut(&T) -> bool,
+        hasher: impl Fn(&T) -> u64,
+    ) -> Result<Bucket<T>, InsertSlot> {
+        self.reserve(1, hasher);
+
+        unsafe {
+            // SAFETY:
+            // 1. We know for sure that there is at least one empty `bucket` in the table.
+            // 2. The [`RawTableInner`] must already have properly initialized control bytes since we will
+            //    never expose `RawTable::new_uninitialized` in a public API.
+            // 3. The `find_or_find_insert_slot_inner` function returns the `index` of only the full bucket,
+            //    which is in the range `0..self.buckets()` (since there is at least one empty `bucket` in
+            //    the table), so calling `self.bucket(index)` and `Bucket::as_ref` is safe.
+            match self
+                .table
+                .find_or_find_insert_slot_inner(hash, &mut |index| eq(self.bucket(index).as_ref()))
+            {
+                // SAFETY: See explanation above.
+                Ok(index) => Ok(self.bucket(index)),
+                Err(slot) => Err(slot),
+            }
+        }
+    }
+
+    /// Inserts a new element into the table in the given slot, and returns its
+    /// raw bucket.
+    ///
+    /// # Safety
+    ///
+    /// `slot` must point to a slot previously returned by
+    /// `find_or_find_insert_slot`, and no mutation of the table must have
+    /// occurred since that call.
+    #[inline]
+    pub unsafe fn insert_in_slot(&mut self, hash: u64, slot: InsertSlot, value: T) -> Bucket<T> {
+        let old_ctrl = *self.table.ctrl(slot.index);
+        self.table.record_item_insert_at(slot.index, old_ctrl, hash);
+
+        let bucket = self.bucket(slot.index);
+        bucket.write(value);
+        bucket
+    }
+
+    /// Searches for an element in the table.
+    #[inline]
+    pub fn find(&self, hash: u64, mut eq: impl FnMut(&T) -> bool) -> Option<Bucket<T>> {
+        unsafe {
+            // SAFETY:
+            // 1. The [`RawTableInner`] must already have properly initialized control bytes since we
+            //    will never expose `RawTable::new_uninitialized` in a public API.
+            // 1. The `find_inner` function returns the `index` of only the full bucket, which is in
+            //    the range `0..self.buckets()`, so calling `self.bucket(index)` and `Bucket::as_ref`
+            //    is safe.
+            let result = self
+                .table
+                .find_inner(hash, &mut |index| eq(self.bucket(index).as_ref()));
+
+            // Avoid `Option::map` because it bloats LLVM IR.
+            match result {
+                // SAFETY: See explanation above.
+                Some(index) => Some(self.bucket(index)),
+                None => None,
+            }
+        }
+    }
+
+    /// Gets a reference to an element in the table.
+    #[inline]
+    pub fn get(&self, hash: u64, eq: impl FnMut(&T) -> bool) -> Option<&T> {
+        // Avoid `Option::map` because it bloats LLVM IR.
+        match self.find(hash, eq) {
+            Some(bucket) => Some(unsafe { bucket.as_ref() }),
+            None => None,
+        }
+    }
+
+    /// Gets a mutable reference to an element in the table.
+    #[inline]
+    pub fn get_mut(&mut self, hash: u64, eq: impl FnMut(&T) -> bool) -> Option<&mut T> {
+        // Avoid `Option::map` because it bloats LLVM IR.
+        match self.find(hash, eq) {
+            Some(bucket) => Some(unsafe { bucket.as_mut() }),
+            None => None,
+        }
+    }
+
+    /// Attempts to get mutable references to `N` entries in the table at once.
+    ///
+    /// Returns an array of length `N` with the results of each query.
+    ///
+    /// At most one mutable reference will be returned to any entry. `None` will be returned if any
+    /// of the hashes are duplicates. `None` will be returned if the hash is not found.
+    ///
+    /// The `eq` argument should be a closure such that `eq(i, k)` returns true if `k` is equal to
+    /// the `i`th key to be looked up.
+    pub fn get_many_mut<const N: usize>(
+        &mut self,
+        hashes: [u64; N],
+        eq: impl FnMut(usize, &T) -> bool,
+    ) -> Option<[&'_ mut T; N]> {
+        unsafe {
+            let ptrs = self.get_many_mut_pointers(hashes, eq)?;
+
+            for (i, &cur) in ptrs.iter().enumerate() {
+                if ptrs[..i].iter().any(|&prev| ptr::eq::<T>(prev, cur)) {
+                    return None;
+                }
+            }
+            // All bucket are distinct from all previous buckets so we're clear to return the result
+            // of the lookup.
+
+            // TODO use `MaybeUninit::array_assume_init` here instead once that's stable.
+            Some(mem::transmute_copy(&ptrs))
+        }
+    }
+
+    pub unsafe fn get_many_unchecked_mut<const N: usize>(
+        &mut self,
+        hashes: [u64; N],
+        eq: impl FnMut(usize, &T) -> bool,
+    ) -> Option<[&'_ mut T; N]> {
+        let ptrs = self.get_many_mut_pointers(hashes, eq)?;
+        Some(mem::transmute_copy(&ptrs))
+    }
+
+    unsafe fn get_many_mut_pointers<const N: usize>(
+        &mut self,
+        hashes: [u64; N],
+        mut eq: impl FnMut(usize, &T) -> bool,
+    ) -> Option<[*mut T; N]> {
+        // TODO use `MaybeUninit::uninit_array` here instead once that's stable.
+        let mut outs: MaybeUninit<[*mut T; N]> = MaybeUninit::uninit();
+        let outs_ptr = outs.as_mut_ptr();
+
+        for (i, &hash) in hashes.iter().enumerate() {
+            let cur = self.find(hash, |k| eq(i, k))?;
+            *(*outs_ptr).get_unchecked_mut(i) = cur.as_mut();
+        }
+
+        // TODO use `MaybeUninit::array_assume_init` here instead once that's stable.
+        Some(outs.assume_init())
+    }
+
+    /// Returns the number of elements the map can hold without reallocating.
+    ///
+    /// This number is a lower bound; the table might be able to hold
+    /// more, but is guaranteed to be able to hold at least this many.
+    #[inline]
+    pub fn capacity(&self) -> usize {
+        self.table.items + self.table.growth_left
+    }
+
+    /// Returns the number of elements in the table.
+    #[inline]
+    pub fn len(&self) -> usize {
+        self.table.items
+    }
+
+    /// Returns `true` if the table contains no elements.
+    #[inline]
+    pub fn is_empty(&self) -> bool {
+        self.len() == 0
+    }
+
+    /// Returns the number of buckets in the table.
+    #[inline]
+    pub fn buckets(&self) -> usize {
+        self.table.bucket_mask + 1
+    }
+
+    /// Checks whether the bucket at `index` is full.
+    ///
+    /// # Safety
+    ///
+    /// The caller must ensure `index` is less than the number of buckets.
+    #[inline]
+    pub unsafe fn is_bucket_full(&self, index: usize) -> bool {
+        self.table.is_bucket_full(index)
+    }
+
+    /// Returns an iterator over every element in the table. It is up to
+    /// the caller to ensure that the `RawTable` outlives the `RawIter`.
+    /// Because we cannot make the `next` method unsafe on the `RawIter`
+    /// struct, we have to make the `iter` method unsafe.
+    #[inline]
+    pub unsafe fn iter(&self) -> RawIter<T> {
+        // SAFETY:
+        // 1. The caller must uphold the safety contract for `iter` method.
+        // 2. The [`RawTableInner`] must already have properly initialized control bytes since
+        //    we will never expose RawTable::new_uninitialized in a public API.
+        self.table.iter()
+    }
+
+    /// Returns an iterator over occupied buckets that could match a given hash.
+    ///
+    /// `RawTable` only stores 7 bits of the hash value, so this iterator may
+    /// return items that have a hash value different than the one provided. You
+    /// should always validate the returned values before using them.
+    ///
+    /// It is up to the caller to ensure that the `RawTable` outlives the
+    /// `RawIterHash`. Because we cannot make the `next` method unsafe on the
+    /// `RawIterHash` struct, we have to make the `iter_hash` method unsafe.
+    #[cfg_attr(feature = "inline-more", inline)]
+    #[cfg(feature = "raw")]
+    pub unsafe fn iter_hash(&self, hash: u64) -> RawIterHash<T> {
+        RawIterHash::new(self, hash)
+    }
+
+    /// Returns an iterator which removes all elements from the table without
+    /// freeing the memory.
+    #[cfg_attr(feature = "inline-more", inline)]
+    pub fn drain(&mut self) -> RawDrain<'_, T, A> {
+        unsafe {
+            let iter = self.iter();
+            self.drain_iter_from(iter)
+        }
+    }
+
+    /// Returns an iterator which removes all elements from the table without
+    /// freeing the memory.
+    ///
+    /// Iteration starts at the provided iterator's current location.
+    ///
+    /// It is up to the caller to ensure that the iterator is valid for this
+    /// `RawTable` and covers all items that remain in the table.
+    #[cfg_attr(feature = "inline-more", inline)]
+    pub unsafe fn drain_iter_from(&mut self, iter: RawIter<T>) -> RawDrain<'_, T, A> {
+        debug_assert_eq!(iter.len(), self.len());
+        RawDrain {
+            iter,
+            table: mem::replace(&mut self.table, RawTableInner::NEW),
+            orig_table: NonNull::from(&mut self.table),
+            marker: PhantomData,
+        }
+    }
+
+    /// Returns an iterator which consumes all elements from the table.
+    ///
+    /// Iteration starts at the provided iterator's current location.
+    ///
+    /// It is up to the caller to ensure that the iterator is valid for this
+    /// `RawTable` and covers all items that remain in the table.
+    pub unsafe fn into_iter_from(self, iter: RawIter<T>) -> RawIntoIter<T, A> {
+        debug_assert_eq!(iter.len(), self.len());
+
+        let allocation = self.into_allocation();
+        RawIntoIter {
+            iter,
+            allocation,
+            marker: PhantomData,
+        }
+    }
+
+    /// Converts the table into a raw allocation. The contents of the table
+    /// should be dropped using a `RawIter` before freeing the allocation.
+    #[cfg_attr(feature = "inline-more", inline)]
+    pub(crate) fn into_allocation(self) -> Option<(NonNull<u8>, Layout, A)> {
+        let alloc = if self.table.is_empty_singleton() {
+            None
+        } else {
+            // Avoid `Option::unwrap_or_else` because it bloats LLVM IR.
+            let (layout, ctrl_offset) =
+                match Self::TABLE_LAYOUT.calculate_layout_for(self.table.buckets()) {
+                    Some(lco) => lco,
+                    None => unsafe { hint::unreachable_unchecked() },
+                };
+            Some((
+                unsafe { NonNull::new_unchecked(self.table.ctrl.as_ptr().sub(ctrl_offset)) },
+                layout,
+                unsafe { ptr::read(&self.alloc) },
+            ))
+        };
+        mem::forget(self);
+        alloc
+    }
+}
+
+unsafe impl<T, A: Allocator> Send for RawTable<T, A>
+where
+    T: Send,
+    A: Send,
+{
+}
+unsafe impl<T, A: Allocator> Sync for RawTable<T, A>
+where
+    T: Sync,
+    A: Sync,
+{
+}
+
+impl RawTableInner {
+    const NEW: Self = RawTableInner::new();
+
+    /// Creates a new empty hash table without allocating any memory.
+    ///
+    /// In effect this returns a table with exactly 1 bucket. However we can
+    /// leave the data pointer dangling since that bucket is never accessed
+    /// due to our load factor forcing us to always have at least 1 free bucket.
+    #[inline]
+    const fn new() -> Self {
+        Self {
+            // Be careful to cast the entire slice to a raw pointer.
+            ctrl: unsafe { NonNull::new_unchecked(Group::static_empty() as *const _ as *mut u8) },
+            bucket_mask: 0,
+            items: 0,
+            growth_left: 0,
+        }
+    }
+}
+
+impl RawTableInner {
+    /// Allocates a new [`RawTableInner`] with the given number of buckets.
+    /// The control bytes and buckets are left uninitialized.
+    ///
+    /// # Safety
+    ///
+    /// The caller of this function must ensure that the `buckets` is power of two
+    /// and also initialize all control bytes of the length `self.bucket_mask + 1 +
+    /// Group::WIDTH` with the [`EMPTY`] bytes.
+    ///
+    /// See also [`Allocator`] API for other safety concerns.
+    ///
+    /// [`Allocator`]: https://doc.rust-lang.org/alloc/alloc/trait.Allocator.html
+    #[cfg_attr(feature = "inline-more", inline)]
+    unsafe fn new_uninitialized<A>(
+        alloc: &A,
+        table_layout: TableLayout,
+        buckets: usize,
+        fallibility: Fallibility,
+    ) -> Result<Self, TryReserveError>
+    where
+        A: Allocator,
+    {
+        debug_assert!(buckets.is_power_of_two());
+
+        // Avoid `Option::ok_or_else` because it bloats LLVM IR.
+        let (layout, ctrl_offset) = match table_layout.calculate_layout_for(buckets) {
+            Some(lco) => lco,
+            None => return Err(fallibility.capacity_overflow()),
+        };
+
+        let ptr: NonNull<u8> = match do_alloc(alloc, layout) {
+            Ok(block) => block.cast(),
+            Err(_) => return Err(fallibility.alloc_err(layout)),
+        };
+
+        // SAFETY: null pointer will be caught in above check
+        let ctrl = NonNull::new_unchecked(ptr.as_ptr().add(ctrl_offset));
+        Ok(Self {
+            ctrl,
+            bucket_mask: buckets - 1,
+            items: 0,
+            growth_left: bucket_mask_to_capacity(buckets - 1),
+        })
+    }
+
+    /// Attempts to allocate a new [`RawTableInner`] with at least enough
+    /// capacity for inserting the given number of elements without reallocating.
+    ///
+    /// All the control bytes are initialized with the [`EMPTY`] bytes.
+    #[inline]
+    fn fallible_with_capacity<A>(
+        alloc: &A,
+        table_layout: TableLayout,
+        capacity: usize,
+        fallibility: Fallibility,
+    ) -> Result<Self, TryReserveError>
+    where
+        A: Allocator,
+    {
+        if capacity == 0 {
+            Ok(Self::NEW)
+        } else {
+            // SAFETY: We checked that we could successfully allocate the new table, and then
+            // initialized all control bytes with the constant `EMPTY` byte.
+            unsafe {
+                let buckets =
+                    capacity_to_buckets(capacity).ok_or_else(|| fallibility.capacity_overflow())?;
+
+                let result = Self::new_uninitialized(alloc, table_layout, buckets, fallibility)?;
+                // SAFETY: We checked that the table is allocated and therefore the table already has
+                // `self.bucket_mask + 1 + Group::WIDTH` number of control bytes (see TableLayout::calculate_layout_for)
+                // so writing `self.num_ctrl_bytes() == bucket_mask + 1 + Group::WIDTH` bytes is safe.
+                result.ctrl(0).write_bytes(EMPTY, result.num_ctrl_bytes());
+
+                Ok(result)
+            }
+        }
+    }
+
+    /// Allocates a new [`RawTableInner`] with at least enough capacity for inserting
+    /// the given number of elements without reallocating.
+    ///
+    /// Panics if the new capacity exceeds [`isize::MAX`] bytes and [`abort`] the program
+    /// in case of allocation error. Use [`fallible_with_capacity`] instead if you want to
+    /// handle memory allocation failure.
+    ///
+    /// All the control bytes are initialized with the [`EMPTY`] bytes.
+    ///
+    /// [`fallible_with_capacity`]: RawTableInner::fallible_with_capacity
+    /// [`abort`]: https://doc.rust-lang.org/alloc/alloc/fn.handle_alloc_error.html
+    fn with_capacity<A>(alloc: &A, table_layout: TableLayout, capacity: usize) -> Self
+    where
+        A: Allocator,
+    {
+        // Avoid `Result::unwrap_or_else` because it bloats LLVM IR.
+        match Self::fallible_with_capacity(alloc, table_layout, capacity, Fallibility::Infallible) {
+            Ok(table_inner) => table_inner,
+            // SAFETY: All allocation errors will be caught inside `RawTableInner::new_uninitialized`.
+            Err(_) => unsafe { hint::unreachable_unchecked() },
+        }
+    }
+
+    /// Fixes up an insertion slot returned by the [`RawTableInner::find_insert_slot_in_group`] method.
+    ///
+    /// In tables smaller than the group width (`self.buckets() < Group::WIDTH`), trailing control
+    /// bytes outside the range of the table are filled with [`EMPTY`] entries. These will unfortunately
+    /// trigger a match of [`RawTableInner::find_insert_slot_in_group`] function. This is because
+    /// the `Some(bit)` returned by `group.match_empty_or_deleted().lowest_set_bit()` after masking
+    /// (`(probe_seq.pos + bit) & self.bucket_mask`) may point to a full bucket that is already occupied.
+    /// We detect this situation here and perform a second scan starting at the beginning of the table.
+    /// This second scan is guaranteed to find an empty slot (due to the load factor) before hitting the
+    /// trailing control bytes (containing [`EMPTY`] bytes).
+    ///
+    /// If this function is called correctly, it is guaranteed to return [`InsertSlot`] with an
+    /// index of an empty or deleted bucket in the range `0..self.buckets()` (see `Warning` and
+    /// `Safety`).
+    ///
+    /// # Warning
+    ///
+    /// The table must have at least 1 empty or deleted `bucket`, otherwise if the table is less than
+    /// the group width (`self.buckets() < Group::WIDTH`) this function returns an index outside of the
+    /// table indices range `0..self.buckets()` (`0..=self.bucket_mask`). Attempt to write data at that
+    /// index will cause immediate [`undefined behavior`].
+    ///
+    /// # Safety
+    ///
+    /// The safety rules are directly derived from the safety rules for [`RawTableInner::ctrl`] method.
+    /// Thus, in order to uphold those safety contracts, as well as for the correct logic of the work
+    /// of this crate, the following rules are necessary and sufficient:
+    ///
+    /// * The [`RawTableInner`] must have properly initialized control bytes otherwise calling this
+    ///   function results in [`undefined behavior`].
+    ///
+    /// * This function must only be used on insertion slots found by [`RawTableInner::find_insert_slot_in_group`]
+    ///   (after the `find_insert_slot_in_group` function, but before insertion into the table).
+    ///
+    /// * The `index` must not be greater than the `self.bucket_mask`, i.e. `(index + 1) <= self.buckets()`
+    ///   (this one is provided by the [`RawTableInner::find_insert_slot_in_group`] function).
+    ///
+    /// Calling this function with an index not provided by [`RawTableInner::find_insert_slot_in_group`]
+    /// may result in [`undefined behavior`] even if the index satisfies the safety rules of the
+    /// [`RawTableInner::ctrl`] function (`index < self.bucket_mask + 1 + Group::WIDTH`).
+    ///
+    /// [`RawTableInner::ctrl`]: RawTableInner::ctrl
+    /// [`RawTableInner::find_insert_slot_in_group`]: RawTableInner::find_insert_slot_in_group
+    /// [`undefined behavior`]: https://doc.rust-lang.org/reference/behavior-considered-undefined.html
+    #[inline]
+    unsafe fn fix_insert_slot(&self, mut index: usize) -> InsertSlot {
+        // SAFETY: The caller of this function ensures that `index` is in the range `0..=self.bucket_mask`.
+        if unlikely(self.is_bucket_full(index)) {
+            debug_assert!(self.bucket_mask < Group::WIDTH);
+            // SAFETY:
+            //
+            // * Since the caller of this function ensures that the control bytes are properly
+            //   initialized and `ptr = self.ctrl(0)` points to the start of the array of control
+            //   bytes, therefore: `ctrl` is valid for reads, properly aligned to `Group::WIDTH`
+            //   and points to the properly initialized control bytes (see also
+            //   `TableLayout::calculate_layout_for` and `ptr::read`);
+            //
+            // * Because the caller of this function ensures that the index was provided by the
+            //   `self.find_insert_slot_in_group()` function, so for for tables larger than the
+            //   group width (self.buckets() >= Group::WIDTH), we will never end up in the given
+            //   branch, since `(probe_seq.pos + bit) & self.bucket_mask` in `find_insert_slot_in_group`
+            //   cannot return a full bucket index. For tables smaller than the group width, calling
+            //   the `unwrap_unchecked` function is also safe, as the trailing control bytes outside
+            //   the range of the table are filled with EMPTY bytes (and we know for sure that there
+            //   is at least one FULL bucket), so this second scan either finds an empty slot (due to
+            //   the load factor) or hits the trailing control bytes (containing EMPTY).
+            index = Group::load_aligned(self.ctrl(0))
+                .match_empty_or_deleted()
+                .lowest_set_bit()
+                .unwrap_unchecked();
+        }
+        InsertSlot { index }
+    }
+
+    /// Finds the position to insert something in a group.
+    ///
+    /// **This may have false positives and must be fixed up with `fix_insert_slot`
+    /// before it's used.**
+    ///
+    /// The function is guaranteed to return the index of an empty or deleted [`Bucket`]
+    /// in the range `0..self.buckets()` (`0..=self.bucket_mask`).
+    #[inline]
+    fn find_insert_slot_in_group(&self, group: &Group, probe_seq: &ProbeSeq) -> Option<usize> {
+        let bit = group.match_empty_or_deleted().lowest_set_bit();
+
+        if likely(bit.is_some()) {
+            // This is the same as `(probe_seq.pos + bit) % self.buckets()` because the number
+            // of buckets is a power of two, and `self.bucket_mask = self.buckets() - 1`.
+            Some((probe_seq.pos + bit.unwrap()) & self.bucket_mask)
+        } else {
+            None
+        }
+    }
+
+    /// Searches for an element in the table, or a potential slot where that element could
+    /// be inserted (an empty or deleted [`Bucket`] index).
+    ///
+    /// This uses dynamic dispatch to reduce the amount of code generated, but that is
+    /// eliminated by LLVM optimizations.
+    ///
+    /// This function does not make any changes to the `data` part of the table, or any
+    /// changes to the `items` or `growth_left` field of the table.
+    ///
+    /// The table must have at least 1 empty or deleted `bucket`, otherwise, if the
+    /// `eq: &mut dyn FnMut(usize) -> bool` function does not return `true`, this function
+    /// will never return (will go into an infinite loop) for tables larger than the group
+    /// width, or return an index outside of the table indices range if the table is less
+    /// than the group width.
+    ///
+    /// This function is guaranteed to provide the `eq: &mut dyn FnMut(usize) -> bool`
+    /// function with only `FULL` buckets' indices and return the `index` of the found
+    /// element (as `Ok(index)`). If the element is not found and there is at least 1
+    /// empty or deleted [`Bucket`] in the table, the function is guaranteed to return
+    /// [InsertSlot] with an index in the range `0..self.buckets()`, but in any case,
+    /// if this function returns [`InsertSlot`], it will contain an index in the range
+    /// `0..=self.buckets()`.
+    ///
+    /// # Safety
+    ///
+    /// The [`RawTableInner`] must have properly initialized control bytes otherwise calling
+    /// this function results in [`undefined behavior`].
+    ///
+    /// Attempt to write data at the [`InsertSlot`] returned by this function when the table is
+    /// less than the group width and if there was not at least one empty or deleted bucket in
+    /// the table will cause immediate [`undefined behavior`]. This is because in this case the
+    /// function will return `self.bucket_mask + 1` as an index due to the trailing [`EMPTY]
+    /// control bytes outside the table range.
+    ///
+    /// [`undefined behavior`]: https://doc.rust-lang.org/reference/behavior-considered-undefined.html
+    #[inline]
+    unsafe fn find_or_find_insert_slot_inner(
+        &self,
+        hash: u64,
+        eq: &mut dyn FnMut(usize) -> bool,
+    ) -> Result<usize, InsertSlot> {
+        let mut insert_slot = None;
+
+        let h2_hash = h2(hash);
+        let mut probe_seq = self.probe_seq(hash);
+
+        loop {
+            // SAFETY:
+            // * Caller of this function ensures that the control bytes are properly initialized.
+            //
+            // * `ProbeSeq.pos` cannot be greater than `self.bucket_mask = self.buckets() - 1`
+            //   of the table due to masking with `self.bucket_mask` and also because mumber of
+            //   buckets is a power of two (see `self.probe_seq` function).
+            //
+            // * Even if `ProbeSeq.pos` returns `position == self.bucket_mask`, it is safe to
+            //   call `Group::load` due to the extended control bytes range, which is
+            //  `self.bucket_mask + 1 + Group::WIDTH` (in fact, this means that the last control
+            //   byte will never be read for the allocated table);
+            //
+            // * Also, even if `RawTableInner` is not already allocated, `ProbeSeq.pos` will
+            //   always return "0" (zero), so Group::load will read unaligned `Group::static_empty()`
+            //   bytes, which is safe (see RawTableInner::new).
+            let group = unsafe { Group::load(self.ctrl(probe_seq.pos)) };
+
+            for bit in group.match_byte(h2_hash) {
+                let index = (probe_seq.pos + bit) & self.bucket_mask;
+
+                if likely(eq(index)) {
+                    return Ok(index);
+                }
+            }
+
+            // We didn't find the element we were looking for in the group, try to get an
+            // insertion slot from the group if we don't have one yet.
+            if likely(insert_slot.is_none()) {
+                insert_slot = self.find_insert_slot_in_group(&group, &probe_seq);
+            }
+
+            // Only stop the search if the group contains at least one empty element.
+            // Otherwise, the element that we are looking for might be in a following group.
+            if likely(group.match_empty().any_bit_set()) {
+                // We must have found a insert slot by now, since the current group contains at
+                // least one. For tables smaller than the group width, there will still be an
+                // empty element in the current (and only) group due to the load factor.
+                unsafe {
+                    // SAFETY:
+                    // * Caller of this function ensures that the control bytes are properly initialized.
+                    //
+                    // * We use this function with the slot / index found by `self.find_insert_slot_in_group`
+                    return Err(self.fix_insert_slot(insert_slot.unwrap_unchecked()));
+                }
+            }
+
+            probe_seq.move_next(self.bucket_mask);
+        }
+    }
+
+    /// Searches for an empty or deleted bucket which is suitable for inserting a new
+    /// element and sets the hash for that slot. Returns an index of that slot and the
+    /// old control byte stored in the found index.
+    ///
+    /// This function does not check if the given element exists in the table. Also,
+    /// this function does not check if there is enough space in the table to insert
+    /// a new element. Caller of the funtion must make ensure that the table has at
+    /// least 1 empty or deleted `bucket`, otherwise this function will never return
+    /// (will go into an infinite loop) for tables larger than the group width, or
+    /// return an index outside of the table indices range if the table is less than
+    /// the group width.
+    ///
+    /// If there is at least 1 empty or deleted `bucket` in the table, the function is
+    /// guaranteed to return an `index` in the range `0..self.buckets()`, but in any case,
+    /// if this function returns an `index` it will be in the range `0..=self.buckets()`.
+    ///
+    /// This function does not make any changes to the `data` parts of the table,
+    /// or any changes to the the `items` or `growth_left` field of the table.
+    ///
+    /// # Safety
+    ///
+    /// The safety rules are directly derived from the safety rules for the
+    /// [`RawTableInner::set_ctrl_h2`] and [`RawTableInner::find_insert_slot`] methods.
+    /// Thus, in order to uphold the safety contracts for that methods, as well as for
+    /// the correct logic of the work of this crate, you must observe the following rules
+    /// when calling this function:
+    ///
+    /// * The [`RawTableInner`] has already been allocated and has properly initialized
+    ///   control bytes otherwise calling this function results in [`undefined behavior`].
+    ///
+    /// * The caller of this function must ensure that the "data" parts of the table
+    ///   will have an entry in the returned index (matching the given hash) right
+    ///   after calling this function.
+    ///
+    /// Attempt to write data at the `index` returned by this function when the table is
+    /// less than the group width and if there was not at least one empty or deleted bucket in
+    /// the table will cause immediate [`undefined behavior`]. This is because in this case the
+    /// function will return `self.bucket_mask + 1` as an index due to the trailing [`EMPTY]
+    /// control bytes outside the table range.
+    ///
+    /// The caller must independently increase the `items` field of the table, and also,
+    /// if the old control byte was [`EMPTY`], then decrease the table's `growth_left`
+    /// field, and do not change it if the old control byte was [`DELETED`].
+    ///
+    /// See also [`Bucket::as_ptr`] method, for more information about of properly removing
+    /// or saving `element` from / into the [`RawTable`] / [`RawTableInner`].
+    ///
+    /// [`Bucket::as_ptr`]: Bucket::as_ptr
+    /// [`undefined behavior`]: https://doc.rust-lang.org/reference/behavior-considered-undefined.html
+    /// [`RawTableInner::ctrl`]: RawTableInner::ctrl
+    /// [`RawTableInner::set_ctrl_h2`]: RawTableInner::set_ctrl_h2
+    /// [`RawTableInner::find_insert_slot`]: RawTableInner::find_insert_slot
+    #[inline]
+    unsafe fn prepare_insert_slot(&mut self, hash: u64) -> (usize, u8) {
+        // SAFETY: Caller of this function ensures that the control bytes are properly initialized.
+        let index: usize = self.find_insert_slot(hash).index;
+        // SAFETY:
+        // 1. The `find_insert_slot` function either returns an `index` less than or
+        //    equal to `self.buckets() = self.bucket_mask + 1` of the table, or never
+        //    returns if it cannot find an empty or deleted slot.
+        // 2. The caller of this function guarantees that the table has already been
+        //    allocated
+        let old_ctrl = *self.ctrl(index);
+        self.set_ctrl_h2(index, hash);
+        (index, old_ctrl)
+    }
+
+    /// Searches for an empty or deleted bucket which is suitable for inserting
+    /// a new element, returning the `index` for the new [`Bucket`].
+    ///
+    /// This function does not make any changes to the `data` part of the table, or any
+    /// changes to the `items` or `growth_left` field of the table.
+    ///
+    /// The table must have at least 1 empty or deleted `bucket`, otherwise this function
+    /// will never return (will go into an infinite loop) for tables larger than the group
+    /// width, or return an index outside of the table indices range if the table is less
+    /// than the group width.
+    ///
+    /// If there is at least 1 empty or deleted `bucket` in the table, the function is
+    /// guaranteed to return [`InsertSlot`] with an index in the range `0..self.buckets()`,
+    /// but in any case, if this function returns [`InsertSlot`], it will contain an index
+    /// in the range `0..=self.buckets()`.
+    ///
+    /// # Safety
+    ///
+    /// The [`RawTableInner`] must have properly initialized control bytes otherwise calling
+    /// this function results in [`undefined behavior`].
+    ///
+    /// Attempt to write data at the [`InsertSlot`] returned by this function when the table is
+    /// less than the group width and if there was not at least one empty or deleted bucket in
+    /// the table will cause immediate [`undefined behavior`]. This is because in this case the
+    /// function will return `self.bucket_mask + 1` as an index due to the trailing [`EMPTY]
+    /// control bytes outside the table range.
+    ///
+    /// [`undefined behavior`]: https://doc.rust-lang.org/reference/behavior-considered-undefined.html
+    #[inline]
+    unsafe fn find_insert_slot(&self, hash: u64) -> InsertSlot {
+        let mut probe_seq = self.probe_seq(hash);
+        loop {
+            // SAFETY:
+            // * Caller of this function ensures that the control bytes are properly initialized.
+            //
+            // * `ProbeSeq.pos` cannot be greater than `self.bucket_mask = self.buckets() - 1`
+            //   of the table due to masking with `self.bucket_mask` and also because mumber of
+            //   buckets is a power of two (see `self.probe_seq` function).
+            //
+            // * Even if `ProbeSeq.pos` returns `position == self.bucket_mask`, it is safe to
+            //   call `Group::load` due to the extended control bytes range, which is
+            //  `self.bucket_mask + 1 + Group::WIDTH` (in fact, this means that the last control
+            //   byte will never be read for the allocated table);
+            //
+            // * Also, even if `RawTableInner` is not already allocated, `ProbeSeq.pos` will
+            //   always return "0" (zero), so Group::load will read unaligned `Group::static_empty()`
+            //   bytes, which is safe (see RawTableInner::new).
+            let group = unsafe { Group::load(self.ctrl(probe_seq.pos)) };
+
+            let index = self.find_insert_slot_in_group(&group, &probe_seq);
+            if likely(index.is_some()) {
+                // SAFETY:
+                // * Caller of this function ensures that the control bytes are properly initialized.
+                //
+                // * We use this function with the slot / index found by `self.find_insert_slot_in_group`
+                unsafe {
+                    return self.fix_insert_slot(index.unwrap_unchecked());
+                }
+            }
+            probe_seq.move_next(self.bucket_mask);
+        }
+    }
+
+    /// Searches for an element in a table, returning the `index` of the found element.
+    /// This uses dynamic dispatch to reduce the amount of code generated, but it is
+    /// eliminated by LLVM optimizations.
+    ///
+    /// This function does not make any changes to the `data` part of the table, or any
+    /// changes to the `items` or `growth_left` field of the table.
+    ///
+    /// The table must have at least 1 empty `bucket`, otherwise, if the
+    /// `eq: &mut dyn FnMut(usize) -> bool` function does not return `true`,
+    /// this function will also never return (will go into an infinite loop).
+    ///
+    /// This function is guaranteed to provide the `eq: &mut dyn FnMut(usize) -> bool`
+    /// function with only `FULL` buckets' indices and return the `index` of the found
+    /// element as `Some(index)`, so the index will always be in the range
+    /// `0..self.buckets()`.
+    ///
+    /// # Safety
+    ///
+    /// The [`RawTableInner`] must have properly initialized control bytes otherwise calling
+    /// this function results in [`undefined behavior`].
+    ///
+    /// [`undefined behavior`]: https://doc.rust-lang.org/reference/behavior-considered-undefined.html
+    #[inline(always)]
+    unsafe fn find_inner(&self, hash: u64, eq: &mut dyn FnMut(usize) -> bool) -> Option<usize> {
+        let h2_hash = h2(hash);
+        let mut probe_seq = self.probe_seq(hash);
+
+        loop {
+            // SAFETY:
+            // * Caller of this function ensures that the control bytes are properly initialized.
+            //
+            // * `ProbeSeq.pos` cannot be greater than `self.bucket_mask = self.buckets() - 1`
+            //   of the table due to masking with `self.bucket_mask`.
+            //
+            // * Even if `ProbeSeq.pos` returns `position == self.bucket_mask`, it is safe to
+            //   call `Group::load` due to the extended control bytes range, which is
+            //  `self.bucket_mask + 1 + Group::WIDTH` (in fact, this means that the last control
+            //   byte will never be read for the allocated table);
+            //
+            // * Also, even if `RawTableInner` is not already allocated, `ProbeSeq.pos` will
+            //   always return "0" (zero), so Group::load will read unaligned `Group::static_empty()`
+            //   bytes, which is safe (see RawTableInner::new_in).
+            let group = unsafe { Group::load(self.ctrl(probe_seq.pos)) };
+
+            for bit in group.match_byte(h2_hash) {
+                // This is the same as `(probe_seq.pos + bit) % self.buckets()` because the number
+                // of buckets is a power of two, and `self.bucket_mask = self.buckets() - 1`.
+                let index = (probe_seq.pos + bit) & self.bucket_mask;
+
+                if likely(eq(index)) {
+                    return Some(index);
+                }
+            }
+
+            if likely(group.match_empty().any_bit_set()) {
+                return None;
+            }
+
+            probe_seq.move_next(self.bucket_mask);
+        }
+    }
+
+    /// Prepares for rehashing data in place (that is, without allocating new memory).
+    /// Converts all full index `control bytes` to `DELETED` and all `DELETED` control
+    /// bytes to `EMPTY`, i.e. performs the following conversion:
+    ///
+    /// - `EMPTY` control bytes   -> `EMPTY`;
+    /// - `DELETED` control bytes -> `EMPTY`;
+    /// - `FULL` control bytes    -> `DELETED`.
+    ///
+    /// This function does not make any changes to the `data` parts of the table,
+    /// or any changes to the the `items` or `growth_left` field of the table.
+    ///
+    /// # Safety
+    ///
+    /// You must observe the following safety rules when calling this function:
+    ///
+    /// * The [`RawTableInner`] has already been allocated;
+    ///
+    /// * The caller of this function must convert the `DELETED` bytes back to `FULL`
+    ///   bytes when re-inserting them into their ideal position (which was impossible
+    ///   to do during the first insert due to tombstones). If the caller does not do
+    ///   this, then calling this function may result in a memory leak.
+    ///
+    /// * The [`RawTableInner`] must have properly initialized control bytes otherwise
+    ///   calling this function results in [`undefined behavior`].
+    ///
+    /// Calling this function on a table that has not been allocated results in
+    /// [`undefined behavior`].
+    ///
+    /// See also [`Bucket::as_ptr`] method, for more information about of properly removing
+    /// or saving `data element` from / into the [`RawTable`] / [`RawTableInner`].
+    ///
+    /// [`Bucket::as_ptr`]: Bucket::as_ptr
+    /// [`undefined behavior`]: https://doc.rust-lang.org/reference/behavior-considered-undefined.html
+    #[allow(clippy::mut_mut)]
+    #[inline]
+    unsafe fn prepare_rehash_in_place(&mut self) {
+        // Bulk convert all full control bytes to DELETED, and all DELETED control bytes to EMPTY.
+        // This effectively frees up all buckets containing a DELETED entry.
+        //
+        // SAFETY:
+        // 1. `i` is guaranteed to be within bounds since we are iterating from zero to `buckets - 1`;
+        // 2. Even if `i` will be `i == self.bucket_mask`, it is safe to call `Group::load_aligned`
+        //    due to the extended control bytes range, which is `self.bucket_mask + 1 + Group::WIDTH`;
+        // 3. The caller of this function guarantees that [`RawTableInner`] has already been allocated;
+        // 4. We can use `Group::load_aligned` and `Group::store_aligned` here since we start from 0
+        //    and go to the end with a step equal to `Group::WIDTH` (see TableLayout::calculate_layout_for).
+        for i in (0..self.buckets()).step_by(Group::WIDTH) {
+            let group = Group::load_aligned(self.ctrl(i));
+            let group = group.convert_special_to_empty_and_full_to_deleted();
+            group.store_aligned(self.ctrl(i));
+        }
+
+        // Fix up the trailing control bytes. See the comments in set_ctrl
+        // for the handling of tables smaller than the group width.
+        //
+        // SAFETY: The caller of this function guarantees that [`RawTableInner`]
+        // has already been allocated
+        if unlikely(self.buckets() < Group::WIDTH) {
+            // SAFETY: We have `self.bucket_mask + 1 + Group::WIDTH` number of control bytes,
+            // so copying `self.buckets() == self.bucket_mask + 1` bytes with offset equal to
+            // `Group::WIDTH` is safe
+            self.ctrl(0)
+                .copy_to(self.ctrl(Group::WIDTH), self.buckets());
+        } else {
+            // SAFETY: We have `self.bucket_mask + 1 + Group::WIDTH` number of
+            // control bytes,so copying `Group::WIDTH` bytes with offset equal
+            // to `self.buckets() == self.bucket_mask + 1` is safe
+            self.ctrl(0)
+                .copy_to(self.ctrl(self.buckets()), Group::WIDTH);
+        }
+    }
+
+    /// Returns an iterator over every element in the table.
+    ///
+    /// # Safety
+    ///
+    /// If any of the following conditions are violated, the result
+    /// is [`undefined behavior`]:
+    ///
+    /// * The caller has to ensure that the `RawTableInner` outlives the
+    ///   `RawIter`. Because we cannot make the `next` method unsafe on
+    ///   the `RawIter` struct, we have to make the `iter` method unsafe.
+    ///
+    /// * The [`RawTableInner`] must have properly initialized control bytes.
+    ///
+    /// [`undefined behavior`]: https://doc.rust-lang.org/reference/behavior-considered-undefined.html
+    #[inline]
+    unsafe fn iter<T>(&self) -> RawIter<T> {
+        // SAFETY:
+        // 1. Since the caller of this function ensures that the control bytes
+        //    are properly initialized and `self.data_end()` points to the start
+        //    of the array of control bytes, therefore: `ctrl` is valid for reads,
+        //    properly aligned to `Group::WIDTH` and points to the properly initialized
+        //    control bytes.
+        // 2. `data` bucket index in the table is equal to the `ctrl` index (i.e.
+        //    equal to zero).
+        // 3. We pass the exact value of buckets of the table to the function.
+        //
+        //                         `ctrl` points here (to the start
+        //                         of the first control byte `CT0`)
+        //                          ∨
+        // [Pad], T_n, ..., T1, T0, |CT0, CT1, ..., CT_n|, Group::WIDTH
+        //                           \________  ________/
+        //                                    \/
+        //       `n = buckets - 1`, i.e. `RawIndexTableInner::buckets() - 1`
+        //
+        // where: T0...T_n  - our stored data;
+        //        CT0...CT_n - control bytes or metadata for `data`.
+        let data = Bucket::from_base_index(self.data_end(), 0);
+        RawIter {
+            // SAFETY: See explanation above
+            iter: RawIterRange::new(self.ctrl.as_ptr(), data, self.buckets()),
+            items: self.items,
+        }
+    }
+
+    /// Executes the destructors (if any) of the values stored in the table.
+    ///
+    /// # Note
+    ///
+    /// This function does not erase the control bytes of the table and does
+    /// not make any changes to the `items` or `growth_left` fields of the
+    /// table. If necessary, the caller of this function must manually set
+    /// up these table fields, for example using the [`clear_no_drop`] function.
+    ///
+    /// Be careful during calling this function, because drop function of
+    /// the elements can panic, and this can leave table in an inconsistent
+    /// state.
+    ///
+    /// # Safety
+    ///
+    /// If `T` is a type that should be dropped and **the table is not empty**,
+    /// calling this function more than once results in [`undefined behavior`].
+    ///
+    /// If `T` is not [`Copy`], attempting to use values stored in the table after
+    /// calling this function may result in [`undefined behavior`].
+    ///
+    /// It is safe to call this function on a table that has not been allocated,
+    /// on a table with uninitialized control bytes, and on a table with no actual
+    /// data but with `Full` control bytes if `self.items == 0`.
+    ///
+    /// See also [`Bucket::drop`] / [`Bucket::as_ptr`] methods, for more information
+    /// about of properly removing or saving `element` from / into the [`RawTable`] /
+    /// [`RawTableInner`].
+    ///
+    /// [`Bucket::drop`]: Bucket::drop
+    /// [`Bucket::as_ptr`]: Bucket::as_ptr
+    /// [`clear_no_drop`]: RawTableInner::clear_no_drop
+    /// [`undefined behavior`]: https://doc.rust-lang.org/reference/behavior-considered-undefined.html
+    unsafe fn drop_elements<T>(&mut self) {
+        // Check that `self.items != 0`. Protects against the possibility
+        // of creating an iterator on an table with uninitialized control bytes.
+        if T::NEEDS_DROP && self.items != 0 {
+            // SAFETY: We know for sure that RawTableInner will outlive the
+            // returned `RawIter` iterator, and the caller of this function
+            // must uphold the safety contract for `drop_elements` method.
+            for item in self.iter::<T>() {
+                // SAFETY: The caller must uphold the safety contract for
+                // `drop_elements` method.
+                item.drop();
+            }
+        }
+    }
+
+    /// Executes the destructors (if any) of the values stored in the table and than
+    /// deallocates the table.
+    ///
+    /// # Note
+    ///
+    /// Calling this function automatically makes invalid (dangling) all instances of
+    /// buckets ([`Bucket`]) and makes invalid (dangling) the `ctrl` field of the table.
+    ///
+    /// This function does not make any changes to the `bucket_mask`, `items` or `growth_left`
+    /// fields of the table. If necessary, the caller of this function must manually set
+    /// up these table fields.
+    ///
+    /// # Safety
+    ///
+    /// If any of the following conditions are violated, the result is [`undefined behavior`]:
+    ///
+    /// * Calling this function more than once;
+    ///
+    /// * The `alloc` must be the same [`Allocator`] as the `Allocator` that was used
+    ///   to allocate this table.
+    ///
+    /// * The `table_layout` must be the same [`TableLayout`] as the `TableLayout` that
+    ///   was used to allocate this table.
+    ///
+    /// The caller of this function should pay attention to the possibility of the
+    /// elements' drop function panicking, because this:
+    ///
+    ///    * May leave the table in an inconsistent state;
+    ///
+    ///    * Memory is never deallocated, so a memory leak may occur.
+    ///
+    /// Attempt to use the `ctrl` field of the table (dereference) after calling this
+    /// function results in [`undefined behavior`].
+    ///
+    /// It is safe to call this function on a table that has not been allocated,
+    /// on a table with uninitialized control bytes, and on a table with no actual
+    /// data but with `Full` control bytes if `self.items == 0`.
+    ///
+    /// See also [`RawTableInner::drop_elements`] or [`RawTableInner::free_buckets`]
+    /// for more  information.
+    ///
+    /// [`RawTableInner::drop_elements`]: RawTableInner::drop_elements
+    /// [`RawTableInner::free_buckets`]: RawTableInner::free_buckets
+    /// [`undefined behavior`]: https://doc.rust-lang.org/reference/behavior-considered-undefined.html
+    unsafe fn drop_inner_table<T, A: Allocator>(&mut self, alloc: &A, table_layout: TableLayout) {
+        if !self.is_empty_singleton() {
+            unsafe {
+                // SAFETY: The caller must uphold the safety contract for `drop_inner_table` method.
+                self.drop_elements::<T>();
+                // SAFETY:
+                // 1. We have checked that our table is allocated.
+                // 2. The caller must uphold the safety contract for `drop_inner_table` method.
+                self.free_buckets(alloc, table_layout);
+            }
+        }
+    }
+
+    #[inline]
+    unsafe fn bucket<T>(&self, index: usize) -> Bucket<T> {
+        debug_assert_ne!(self.bucket_mask, 0);
+        debug_assert!(index < self.buckets());
+        Bucket::from_base_index(self.data_end(), index)
+    }
+
+    #[inline]
+    unsafe fn bucket_ptr(&self, index: usize, size_of: usize) -> *mut u8 {
+        debug_assert_ne!(self.bucket_mask, 0);
+        debug_assert!(index < self.buckets());
+        let base: *mut u8 = self.data_end().as_ptr();
+        base.sub((index + 1) * size_of)
+    }
+
+    #[inline]
+    unsafe fn data_end<T>(&self) -> NonNull<T> {
+        NonNull::new_unchecked(self.ctrl.as_ptr().cast())
+    }
+
+    /// Returns an iterator-like object for a probe sequence on the table.
+    ///
+    /// This iterator never terminates, but is guaranteed to visit each bucket
+    /// group exactly once. The loop using `probe_seq` must terminate upon
+    /// reaching a group containing an empty bucket.
+    #[inline]
+    fn probe_seq(&self, hash: u64) -> ProbeSeq {
+        ProbeSeq {
+            // This is the same as `hash as usize % self.buckets()` because the number
+            // of buckets is a power of two, and `self.bucket_mask = self.buckets() - 1`.
+            pos: h1(hash) & self.bucket_mask,
+            stride: 0,
+        }
+    }
+
+    /// Returns the index of a bucket for which a value must be inserted if there is enough rooom
+    /// in the table, otherwise returns error
+    #[cfg(feature = "raw")]
+    #[inline]
+    unsafe fn prepare_insert_no_grow(&mut self, hash: u64) -> Result<usize, ()> {
+        let index = self.find_insert_slot(hash).index;
+        let old_ctrl = *self.ctrl(index);
+        if unlikely(self.growth_left == 0 && special_is_empty(old_ctrl)) {
+            Err(())
+        } else {
+            self.record_item_insert_at(index, old_ctrl, hash);
+            Ok(index)
+        }
+    }
+
+    #[inline]
+    unsafe fn record_item_insert_at(&mut self, index: usize, old_ctrl: u8, hash: u64) {
+        self.growth_left -= usize::from(special_is_empty(old_ctrl));
+        self.set_ctrl_h2(index, hash);
+        self.items += 1;
+    }
+
+    #[inline]
+    fn is_in_same_group(&self, i: usize, new_i: usize, hash: u64) -> bool {
+        let probe_seq_pos = self.probe_seq(hash).pos;
+        let probe_index =
+            |pos: usize| (pos.wrapping_sub(probe_seq_pos) & self.bucket_mask) / Group::WIDTH;
+        probe_index(i) == probe_index(new_i)
+    }
+
+    /// Sets a control byte to the hash, and possibly also the replicated control byte at
+    /// the end of the array.
+    ///
+    /// This function does not make any changes to the `data` parts of the table,
+    /// or any changes to the the `items` or `growth_left` field of the table.
+    ///
+    /// # Safety
+    ///
+    /// The safety rules are directly derived from the safety rules for [`RawTableInner::set_ctrl`]
+    /// method. Thus, in order to uphold the safety contracts for the method, you must observe the
+    /// following rules when calling this function:
+    ///
+    /// * The [`RawTableInner`] has already been allocated;
+    ///
+    /// * The `index` must not be greater than the `RawTableInner.bucket_mask`, i.e.
+    ///   `index <= RawTableInner.bucket_mask` or, in other words, `(index + 1)` must
+    ///   be no greater than the number returned by the function [`RawTableInner::buckets`].
+    ///
+    /// Calling this function on a table that has not been allocated results in [`undefined behavior`].
+    ///
+    /// See also [`Bucket::as_ptr`] method, for more information about of properly removing
+    /// or saving `data element` from / into the [`RawTable`] / [`RawTableInner`].
+    ///
+    /// [`RawTableInner::set_ctrl`]: RawTableInner::set_ctrl
+    /// [`RawTableInner::buckets`]: RawTableInner::buckets
+    /// [`Bucket::as_ptr`]: Bucket::as_ptr
+    /// [`undefined behavior`]: https://doc.rust-lang.org/reference/behavior-considered-undefined.html
+    #[inline]
+    unsafe fn set_ctrl_h2(&mut self, index: usize, hash: u64) {
+        // SAFETY: The caller must uphold the safety rules for the [`RawTableInner::set_ctrl_h2`]
+        self.set_ctrl(index, h2(hash));
+    }
+
+    /// Replaces the hash in the control byte at the given index with the provided one,
+    /// and possibly also replicates the new control byte at the end of the array of control
+    /// bytes, returning the old control byte.
+    ///
+    /// This function does not make any changes to the `data` parts of the table,
+    /// or any changes to the the `items` or `growth_left` field of the table.
+    ///
+    /// # Safety
+    ///
+    /// The safety rules are directly derived from the safety rules for [`RawTableInner::set_ctrl_h2`]
+    /// and [`RawTableInner::ctrl`] methods. Thus, in order to uphold the safety contracts for both
+    /// methods, you must observe the following rules when calling this function:
+    ///
+    /// * The [`RawTableInner`] has already been allocated;
+    ///
+    /// * The `index` must not be greater than the `RawTableInner.bucket_mask`, i.e.
+    ///   `index <= RawTableInner.bucket_mask` or, in other words, `(index + 1)` must
+    ///   be no greater than the number returned by the function [`RawTableInner::buckets`].
+    ///
+    /// Calling this function on a table that has not been allocated results in [`undefined behavior`].
+    ///
+    /// See also [`Bucket::as_ptr`] method, for more information about of properly removing
+    /// or saving `data element` from / into the [`RawTable`] / [`RawTableInner`].
+    ///
+    /// [`RawTableInner::set_ctrl_h2`]: RawTableInner::set_ctrl_h2
+    /// [`RawTableInner::buckets`]: RawTableInner::buckets
+    /// [`Bucket::as_ptr`]: Bucket::as_ptr
+    /// [`undefined behavior`]: https://doc.rust-lang.org/reference/behavior-considered-undefined.html
+    #[inline]
+    unsafe fn replace_ctrl_h2(&mut self, index: usize, hash: u64) -> u8 {
+        // SAFETY: The caller must uphold the safety rules for the [`RawTableInner::replace_ctrl_h2`]
+        let prev_ctrl = *self.ctrl(index);
+        self.set_ctrl_h2(index, hash);
+        prev_ctrl
+    }
+
+    /// Sets a control byte, and possibly also the replicated control byte at
+    /// the end of the array.
+    ///
+    /// This function does not make any changes to the `data` parts of the table,
+    /// or any changes to the the `items` or `growth_left` field of the table.
+    ///
+    /// # Safety
+    ///
+    /// You must observe the following safety rules when calling this function:
+    ///
+    /// * The [`RawTableInner`] has already been allocated;
+    ///
+    /// * The `index` must not be greater than the `RawTableInner.bucket_mask`, i.e.
+    ///   `index <= RawTableInner.bucket_mask` or, in other words, `(index + 1)` must
+    ///   be no greater than the number returned by the function [`RawTableInner::buckets`].
+    ///
+    /// Calling this function on a table that has not been allocated results in [`undefined behavior`].
+    ///
+    /// See also [`Bucket::as_ptr`] method, for more information about of properly removing
+    /// or saving `data element` from / into the [`RawTable`] / [`RawTableInner`].
+    ///
+    /// [`RawTableInner::buckets`]: RawTableInner::buckets
+    /// [`Bucket::as_ptr`]: Bucket::as_ptr
+    /// [`undefined behavior`]: https://doc.rust-lang.org/reference/behavior-considered-undefined.html
+    #[inline]
+    unsafe fn set_ctrl(&mut self, index: usize, ctrl: u8) {
+        // Replicate the first Group::WIDTH control bytes at the end of
+        // the array without using a branch. If the tables smaller than
+        // the group width (self.buckets() < Group::WIDTH),
+        // `index2 = Group::WIDTH + index`, otherwise `index2` is:
+        //
+        // - If index >= Group::WIDTH then index == index2.
+        // - Otherwise index2 == self.bucket_mask + 1 + index.
+        //
+        // The very last replicated control byte is never actually read because
+        // we mask the initial index for unaligned loads, but we write it
+        // anyways because it makes the set_ctrl implementation simpler.
+        //
+        // If there are fewer buckets than Group::WIDTH then this code will
+        // replicate the buckets at the end of the trailing group. For example
+        // with 2 buckets and a group size of 4, the control bytes will look
+        // like this:
+        //
+        //     Real    |             Replicated
+        // ---------------------------------------------
+        // | [A] | [B] | [EMPTY] | [EMPTY] | [A] | [B] |
+        // ---------------------------------------------
+
+        // This is the same as `(index.wrapping_sub(Group::WIDTH)) % self.buckets() + Group::WIDTH`
+        // because the number of buckets is a power of two, and `self.bucket_mask = self.buckets() - 1`.
+        let index2 = ((index.wrapping_sub(Group::WIDTH)) & self.bucket_mask) + Group::WIDTH;
+
+        // SAFETY: The caller must uphold the safety rules for the [`RawTableInner::set_ctrl`]
+        *self.ctrl(index) = ctrl;
+        *self.ctrl(index2) = ctrl;
+    }
+
+    /// Returns a pointer to a control byte.
+    ///
+    /// # Safety
+    ///
+    /// For the allocated [`RawTableInner`], the result is [`Undefined Behavior`],
+    /// if the `index` is greater than the `self.bucket_mask + 1 + Group::WIDTH`.
+    /// In that case, calling this function with `index == self.bucket_mask + 1 + Group::WIDTH`
+    /// will return a pointer to the end of the allocated table and it is useless on its own.
+    ///
+    /// Calling this function with `index >= self.bucket_mask + 1 + Group::WIDTH` on a
+    /// table that has not been allocated results in [`Undefined Behavior`].
+    ///
+    /// So to satisfy both requirements you should always follow the rule that
+    /// `index < self.bucket_mask + 1 + Group::WIDTH`
+    ///
+    /// Calling this function on [`RawTableInner`] that are not already allocated is safe
+    /// for read-only purpose.
+    ///
+    /// See also [`Bucket::as_ptr()`] method, for more information about of properly removing
+    /// or saving `data element` from / into the [`RawTable`] / [`RawTableInner`].
+    ///
+    /// [`Bucket::as_ptr()`]: Bucket::as_ptr()
+    /// [`Undefined Behavior`]: https://doc.rust-lang.org/reference/behavior-considered-undefined.html
+    #[inline]
+    unsafe fn ctrl(&self, index: usize) -> *mut u8 {
+        debug_assert!(index < self.num_ctrl_bytes());
+        // SAFETY: The caller must uphold the safety rules for the [`RawTableInner::ctrl`]
+        self.ctrl.as_ptr().add(index)
+    }
+
+    #[inline]
+    fn buckets(&self) -> usize {
+        self.bucket_mask + 1
+    }
+
+    /// Checks whether the bucket at `index` is full.
+    ///
+    /// # Safety
+    ///
+    /// The caller must ensure `index` is less than the number of buckets.
+    #[inline]
+    unsafe fn is_bucket_full(&self, index: usize) -> bool {
+        debug_assert!(index < self.buckets());
+        is_full(*self.ctrl(index))
+    }
+
+    #[inline]
+    fn num_ctrl_bytes(&self) -> usize {
+        self.bucket_mask + 1 + Group::WIDTH
+    }
+
+    #[inline]
+    fn is_empty_singleton(&self) -> bool {
+        self.bucket_mask == 0
+    }
+
+    /// Attempts to allocate a new hash table with at least enough capacity
+    /// for inserting the given number of elements without reallocating,
+    /// and return it inside ScopeGuard to protect against panic in the hash
+    /// function.
+    ///
+    /// # Note
+    ///
+    /// It is recommended (but not required):
+    ///
+    /// * That the new table's `capacity` be greater than or equal to `self.items`.
+    ///
+    /// * The `alloc` is the same [`Allocator`] as the `Allocator` used
+    ///   to allocate this table.
+    ///
+    /// * The `table_layout` is the same [`TableLayout`] as the `TableLayout` used
+    ///   to allocate this table.
+    ///
+    /// If `table_layout` does not match the `TableLayout` that was used to allocate
+    /// this table, then using `mem::swap` with the `self` and the new table returned
+    /// by this function results in [`undefined behavior`].
+    ///
+    /// [`undefined behavior`]: https://doc.rust-lang.org/reference/behavior-considered-undefined.html
+    #[allow(clippy::mut_mut)]
+    #[inline]
+    fn prepare_resize<'a, A>(
+        &self,
+        alloc: &'a A,
+        table_layout: TableLayout,
+        capacity: usize,
+        fallibility: Fallibility,
+    ) -> Result<crate::scopeguard::ScopeGuard<Self, impl FnMut(&mut Self) + 'a>, TryReserveError>
+    where
+        A: Allocator,
+    {
+        debug_assert!(self.items <= capacity);
+
+        // Allocate and initialize the new table.
+        let new_table =
+            RawTableInner::fallible_with_capacity(alloc, table_layout, capacity, fallibility)?;
+
+        // The hash function may panic, in which case we simply free the new
+        // table without dropping any elements that may have been copied into
+        // it.
+        //
+        // This guard is also used to free the old table on success, see
+        // the comment at the bottom of this function.
+        Ok(guard(new_table, move |self_| {
+            if !self_.is_empty_singleton() {
+                // SAFETY:
+                // 1. We have checked that our table is allocated.
+                // 2. We know for sure that the `alloc` and `table_layout` matches the
+                //    [`Allocator`] and [`TableLayout`] used to allocate this table.
+                unsafe { self_.free_buckets(alloc, table_layout) };
+            }
+        }))
+    }
+
+    /// Reserves or rehashes to make room for `additional` more elements.
+    ///
+    /// This uses dynamic dispatch to reduce the amount of
+    /// code generated, but it is eliminated by LLVM optimizations when inlined.
+    ///
+    /// # Safety
+    ///
+    /// If any of the following conditions are violated, the result is
+    /// [`undefined behavior`]:
+    ///
+    /// * The `alloc` must be the same [`Allocator`] as the `Allocator` used
+    ///   to allocate this table.
+    ///
+    /// * The `layout` must be the same [`TableLayout`] as the `TableLayout`
+    ///   used to allocate this table.
+    ///
+    /// * The `drop` function (`fn(*mut u8)`) must be the actual drop function of
+    ///   the elements stored in the table.
+    ///
+    /// * The [`RawTableInner`] must have properly initialized control bytes.
+    ///
+    /// [`undefined behavior`]: https://doc.rust-lang.org/reference/behavior-considered-undefined.html
+    #[allow(clippy::inline_always)]
+    #[inline(always)]
+    unsafe fn reserve_rehash_inner<A>(
+        &mut self,
+        alloc: &A,
+        additional: usize,
+        hasher: &dyn Fn(&mut Self, usize) -> u64,
+        fallibility: Fallibility,
+        layout: TableLayout,
+        drop: Option<fn(*mut u8)>,
+    ) -> Result<(), TryReserveError>
+    where
+        A: Allocator,
+    {
+        // Avoid `Option::ok_or_else` because it bloats LLVM IR.
+        let new_items = match self.items.checked_add(additional) {
+            Some(new_items) => new_items,
+            None => return Err(fallibility.capacity_overflow()),
+        };
+        let full_capacity = bucket_mask_to_capacity(self.bucket_mask);
+        if new_items <= full_capacity / 2 {
+            // Rehash in-place without re-allocating if we have plenty of spare
+            // capacity that is locked up due to DELETED entries.
+
+            // SAFETY:
+            // 1. We know for sure that `[`RawTableInner`]` has already been allocated
+            //    (since new_items <= full_capacity / 2);
+            // 2. The caller ensures that `drop` function is the actual drop function of
+            //    the elements stored in the table.
+            // 3. The caller ensures that `layout` matches the [`TableLayout`] that was
+            //    used to allocate this table.
+            // 4. The caller ensures that the control bytes of the `RawTableInner`
+            //    are already initialized.
+            self.rehash_in_place(hasher, layout.size, drop);
+            Ok(())
+        } else {
+            // Otherwise, conservatively resize to at least the next size up
+            // to avoid churning deletes into frequent rehashes.
+            //
+            // SAFETY:
+            // 1. We know for sure that `capacity >= self.items`.
+            // 2. The caller ensures that `alloc` and `layout` matches the [`Allocator`] and
+            //    [`TableLayout`] that were used to allocate this table.
+            // 3. The caller ensures that the control bytes of the `RawTableInner`
+            //    are already initialized.
+            self.resize_inner(
+                alloc,
+                usize::max(new_items, full_capacity + 1),
+                hasher,
+                fallibility,
+                layout,
+            )
+        }
+    }
+
+    /// Returns an iterator over full buckets indices in the table.
+    ///
+    /// # Safety
+    ///
+    /// Behavior is undefined if any of the following conditions are violated:
+    ///
+    /// * The caller has to ensure that the `RawTableInner` outlives the
+    ///   `FullBucketsIndices`. Because we cannot make the `next` method
+    ///   unsafe on the `FullBucketsIndices` struct, we have to make the
+    ///   `full_buckets_indices` method unsafe.
+    ///
+    /// * The [`RawTableInner`] must have properly initialized control bytes.
+    #[inline(always)]
+    unsafe fn full_buckets_indices(&self) -> FullBucketsIndices {
+        // SAFETY:
+        // 1. Since the caller of this function ensures that the control bytes
+        //    are properly initialized and `self.ctrl(0)` points to the start
+        //    of the array of control bytes, therefore: `ctrl` is valid for reads,
+        //    properly aligned to `Group::WIDTH` and points to the properly initialized
+        //    control bytes.
+        // 2. The value of `items` is equal to the amount of data (values) added
+        //    to the table.
+        //
+        //                         `ctrl` points here (to the start
+        //                         of the first control byte `CT0`)
+        //                          ∨
+        // [Pad], T_n, ..., T1, T0, |CT0, CT1, ..., CT_n|, Group::WIDTH
+        //                           \________  ________/
+        //                                    \/
+        //       `n = buckets - 1`, i.e. `RawIndexTableInner::buckets() - 1`
+        //
+        // where: T0...T_n  - our stored data;
+        //        CT0...CT_n - control bytes or metadata for `data`.
+        let ctrl = NonNull::new_unchecked(self.ctrl(0));
+
+        FullBucketsIndices {
+            // Load the first group
+            // SAFETY: See explanation above.
+            current_group: Group::load_aligned(ctrl.as_ptr()).match_full().into_iter(),
+            group_first_index: 0,
+            ctrl,
+            items: self.items,
+        }
+    }
+
+    /// Allocates a new table of a different size and moves the contents of the
+    /// current table into it.
+    ///
+    /// This uses dynamic dispatch to reduce the amount of
+    /// code generated, but it is eliminated by LLVM optimizations when inlined.
+    ///
+    /// # Safety
+    ///
+    /// If any of the following conditions are violated, the result is
+    /// [`undefined behavior`]:
+    ///
+    /// * The `alloc` must be the same [`Allocator`] as the `Allocator` used
+    ///   to allocate this table;
+    ///
+    /// * The `layout` must be the same [`TableLayout`] as the `TableLayout`
+    ///   used to allocate this table;
+    ///
+    /// * The [`RawTableInner`] must have properly initialized control bytes.
+    ///
+    /// The caller of this function must ensure that `capacity >= self.items`
+    /// otherwise:
+    ///
+    /// * If `self.items != 0`, calling of this function with `capacity == 0`
+    ///   results in [`undefined behavior`].
+    ///
+    /// * If `capacity_to_buckets(capacity) < Group::WIDTH` and
+    ///   `self.items > capacity_to_buckets(capacity)` calling this function
+    ///   results in [`undefined behavior`].
+    ///
+    /// * If `capacity_to_buckets(capacity) >= Group::WIDTH` and
+    ///   `self.items > capacity_to_buckets(capacity)` calling this function
+    ///   are never return (will go into an infinite loop).
+    ///
+    /// Note: It is recommended (but not required) that the new table's `capacity`
+    /// be greater than or equal to `self.items`. In case if `capacity <= self.items`
+    /// this function can never return. See [`RawTableInner::find_insert_slot`] for
+    /// more information.
+    ///
+    /// [`RawTableInner::find_insert_slot`]: RawTableInner::find_insert_slot
+    /// [`undefined behavior`]: https://doc.rust-lang.org/reference/behavior-considered-undefined.html
+    #[allow(clippy::inline_always)]
+    #[inline(always)]
+    unsafe fn resize_inner<A>(
+        &mut self,
+        alloc: &A,
+        capacity: usize,
+        hasher: &dyn Fn(&mut Self, usize) -> u64,
+        fallibility: Fallibility,
+        layout: TableLayout,
+    ) -> Result<(), TryReserveError>
+    where
+        A: Allocator,
+    {
+        // SAFETY: We know for sure that `alloc` and `layout` matches the [`Allocator`] and [`TableLayout`]
+        // that were used to allocate this table.
+        let mut new_table = self.prepare_resize(alloc, layout, capacity, fallibility)?;
+
+        // SAFETY: We know for sure that RawTableInner will outlive the
+        // returned `FullBucketsIndices` iterator, and the caller of this
+        // function ensures that the control bytes are properly initialized.
+        for full_byte_index in self.full_buckets_indices() {
+            // This may panic.
+            let hash = hasher(self, full_byte_index);
+
+            // SAFETY:
+            // We can use a simpler version of insert() here since:
+            // 1. There are no DELETED entries.
+            // 2. We know there is enough space in the table.
+            // 3. All elements are unique.
+            // 4. The caller of this function guarantees that `capacity > 0`
+            //    so `new_table` must already have some allocated memory.
+            // 5. We set `growth_left` and `items` fields of the new table
+            //    after the loop.
+            // 6. We insert into the table, at the returned index, the data
+            //    matching the given hash immediately after calling this function.
+            let (new_index, _) = new_table.prepare_insert_slot(hash);
+
+            // SAFETY:
+            //
+            // * `src` is valid for reads of `layout.size` bytes, since the
+            //   table is alive and the `full_byte_index` is guaranteed to be
+            //   within bounds (see `FullBucketsIndices::next_impl`);
+            //
+            // * `dst` is valid for writes of `layout.size` bytes, since the
+            //   caller ensures that `table_layout` matches the [`TableLayout`]
+            //   that was used to allocate old table and we have the `new_index`
+            //   returned by `prepare_insert_slot`.
+            //
+            // * Both `src` and `dst` are properly aligned.
+            //
+            // * Both `src` and `dst` point to different region of memory.
+            ptr::copy_nonoverlapping(
+                self.bucket_ptr(full_byte_index, layout.size),
+                new_table.bucket_ptr(new_index, layout.size),
+                layout.size,
+            );
+        }
+
+        // The hash function didn't panic, so we can safely set the
+        // `growth_left` and `items` fields of the new table.
+        new_table.growth_left -= self.items;
+        new_table.items = self.items;
+
+        // We successfully copied all elements without panicking. Now replace
+        // self with the new table. The old table will have its memory freed but
+        // the items will not be dropped (since they have been moved into the
+        // new table).
+        // SAFETY: The caller ensures that `table_layout` matches the [`TableLayout`]
+        // that was used to allocate this table.
+        mem::swap(self, &mut new_table);
+
+        Ok(())
+    }
+
+    /// Rehashes the contents of the table in place (i.e. without changing the
+    /// allocation).
+    ///
+    /// If `hasher` panics then some the table's contents may be lost.
+    ///
+    /// This uses dynamic dispatch to reduce the amount of
+    /// code generated, but it is eliminated by LLVM optimizations when inlined.
+    ///
+    /// # Safety
+    ///
+    /// If any of the following conditions are violated, the result is [`undefined behavior`]:
+    ///
+    /// * The `size_of` must be equal to the size of the elements stored in the table;
+    ///
+    /// * The `drop` function (`fn(*mut u8)`) must be the actual drop function of
+    ///   the elements stored in the table.
+    ///
+    /// * The [`RawTableInner`] has already been allocated;
+    ///
+    /// * The [`RawTableInner`] must have properly initialized control bytes.
+    ///
+    /// [`undefined behavior`]: https://doc.rust-lang.org/reference/behavior-considered-undefined.html
+    #[allow(clippy::inline_always)]
+    #[cfg_attr(feature = "inline-more", inline(always))]
+    #[cfg_attr(not(feature = "inline-more"), inline)]
+    unsafe fn rehash_in_place(
+        &mut self,
+        hasher: &dyn Fn(&mut Self, usize) -> u64,
+        size_of: usize,
+        drop: Option<fn(*mut u8)>,
+    ) {
+        // If the hash function panics then properly clean up any elements
+        // that we haven't rehashed yet. We unfortunately can't preserve the
+        // element since we lost their hash and have no way of recovering it
+        // without risking another panic.
+        self.prepare_rehash_in_place();
+
+        let mut guard = guard(self, move |self_| {
+            if let Some(drop) = drop {
+                for i in 0..self_.buckets() {
+                    if *self_.ctrl(i) == DELETED {
+                        self_.set_ctrl(i, EMPTY);
+                        drop(self_.bucket_ptr(i, size_of));
+                        self_.items -= 1;
+                    }
+                }
+            }
+            self_.growth_left = bucket_mask_to_capacity(self_.bucket_mask) - self_.items;
+        });
+
+        // At this point, DELETED elements are elements that we haven't
+        // rehashed yet. Find them and re-insert them at their ideal
+        // position.
+        'outer: for i in 0..guard.buckets() {
+            if *guard.ctrl(i) != DELETED {
+                continue;
+            }
+
+            let i_p = guard.bucket_ptr(i, size_of);
+
+            'inner: loop {
+                // Hash the current item
+                let hash = hasher(*guard, i);
+
+                // Search for a suitable place to put it
+                //
+                // SAFETY: Caller of this function ensures that the control bytes
+                // are properly initialized.
+                let new_i = guard.find_insert_slot(hash).index;
+
+                // Probing works by scanning through all of the control
+                // bytes in groups, which may not be aligned to the group
+                // size. If both the new and old position fall within the
+                // same unaligned group, then there is no benefit in moving
+                // it and we can just continue to the next item.
+                if likely(guard.is_in_same_group(i, new_i, hash)) {
+                    guard.set_ctrl_h2(i, hash);
+                    continue 'outer;
+                }
+
+                let new_i_p = guard.bucket_ptr(new_i, size_of);
+
+                // We are moving the current item to a new position. Write
+                // our H2 to the control byte of the new position.
+                let prev_ctrl = guard.replace_ctrl_h2(new_i, hash);
+                if prev_ctrl == EMPTY {
+                    guard.set_ctrl(i, EMPTY);
+                    // If the target slot is empty, simply move the current
+                    // element into the new slot and clear the old control
+                    // byte.
+                    ptr::copy_nonoverlapping(i_p, new_i_p, size_of);
+                    continue 'outer;
+                } else {
+                    // If the target slot is occupied, swap the two elements
+                    // and then continue processing the element that we just
+                    // swapped into the old slot.
+                    debug_assert_eq!(prev_ctrl, DELETED);
+                    ptr::swap_nonoverlapping(i_p, new_i_p, size_of);
+                    continue 'inner;
+                }
+            }
+        }
+
+        guard.growth_left = bucket_mask_to_capacity(guard.bucket_mask) - guard.items;
+
+        mem::forget(guard);
+    }
+
+    /// Deallocates the table without dropping any entries.
+    ///
+    /// # Note
+    ///
+    /// This function must be called only after [`drop_elements`](RawTable::drop_elements),
+    /// else it can lead to leaking of memory. Also calling this function automatically
+    /// makes invalid (dangling) all instances of buckets ([`Bucket`]) and makes invalid
+    /// (dangling) the `ctrl` field of the table.
+    ///
+    /// # Safety
+    ///
+    /// If any of the following conditions are violated, the result is [`Undefined Behavior`]:
+    ///
+    /// * The [`RawTableInner`] has already been allocated;
+    ///
+    /// * The `alloc` must be the same [`Allocator`] as the `Allocator` that was used
+    ///   to allocate this table.
+    ///
+    /// * The `table_layout` must be the same [`TableLayout`] as the `TableLayout` that was used
+    ///   to allocate this table.
+    ///
+    /// See also [`GlobalAlloc::dealloc`] or [`Allocator::deallocate`] for more  information.
+    ///
+    /// [`Undefined Behavior`]: https://doc.rust-lang.org/reference/behavior-considered-undefined.html
+    /// [`GlobalAlloc::dealloc`]: https://doc.rust-lang.org/alloc/alloc/trait.GlobalAlloc.html#tymethod.dealloc
+    /// [`Allocator::deallocate`]: https://doc.rust-lang.org/alloc/alloc/trait.Allocator.html#tymethod.deallocate
+    #[inline]
+    unsafe fn free_buckets<A>(&mut self, alloc: &A, table_layout: TableLayout)
+    where
+        A: Allocator,
+    {
+        // SAFETY: The caller must uphold the safety contract for `free_buckets`
+        // method.
+        let (ptr, layout) = self.allocation_info(table_layout);
+        alloc.deallocate(ptr, layout);
+    }
+
+    /// Returns a pointer to the allocated memory and the layout that was used to
+    /// allocate the table.
+    ///
+    /// # Safety
+    ///
+    /// Caller of this function must observe the following safety rules:
+    ///
+    /// * The [`RawTableInner`] has already been allocated, otherwise
+    ///   calling this function results in [`undefined behavior`]
+    ///
+    /// * The `table_layout` must be the same [`TableLayout`] as the `TableLayout`
+    ///   that was used to allocate this table. Failure to comply with this condition
+    ///   may result in [`undefined behavior`].
+    ///
+    /// See also [`GlobalAlloc::dealloc`] or [`Allocator::deallocate`] for more  information.
+    ///
+    /// [`undefined behavior`]: https://doc.rust-lang.org/reference/behavior-considered-undefined.html
+    /// [`GlobalAlloc::dealloc`]: https://doc.rust-lang.org/alloc/alloc/trait.GlobalAlloc.html#tymethod.dealloc
+    /// [`Allocator::deallocate`]: https://doc.rust-lang.org/alloc/alloc/trait.Allocator.html#tymethod.deallocate
+    #[inline]
+    unsafe fn allocation_info(&self, table_layout: TableLayout) -> (NonNull<u8>, Layout) {
+        debug_assert!(
+            !self.is_empty_singleton(),
+            "this function can only be called on non-empty tables"
+        );
+
+        // Avoid `Option::unwrap_or_else` because it bloats LLVM IR.
+        let (layout, ctrl_offset) = match table_layout.calculate_layout_for(self.buckets()) {
+            Some(lco) => lco,
+            None => unsafe { hint::unreachable_unchecked() },
+        };
+        (
+            // SAFETY: The caller must uphold the safety contract for `allocation_info` method.
+            unsafe { NonNull::new_unchecked(self.ctrl.as_ptr().sub(ctrl_offset)) },
+            layout,
+        )
+    }
+
+    /// Returns a pointer to the allocated memory and the layout that was used to
+    /// allocate the table. If [`RawTableInner`] has not been allocated, this
+    /// function return `dangling` pointer and `()` (unit) layout.
+    ///
+    /// # Safety
+    ///
+    /// The `table_layout` must be the same [`TableLayout`] as the `TableLayout`
+    /// that was used to allocate this table. Failure to comply with this condition
+    /// may result in [`undefined behavior`].
+    ///
+    /// See also [`GlobalAlloc::dealloc`] or [`Allocator::deallocate`] for more  information.
+    ///
+    /// [`undefined behavior`]: https://doc.rust-lang.org/reference/behavior-considered-undefined.html
+    /// [`GlobalAlloc::dealloc`]: https://doc.rust-lang.org/alloc/alloc/trait.GlobalAlloc.html#tymethod.dealloc
+    /// [`Allocator::deallocate`]: https://doc.rust-lang.org/alloc/alloc/trait.Allocator.html#tymethod.deallocate
+    #[cfg(feature = "raw")]
+    unsafe fn allocation_info_or_zero(&self, table_layout: TableLayout) -> (NonNull<u8>, Layout) {
+        if self.is_empty_singleton() {
+            (NonNull::dangling(), Layout::new::<()>())
+        } else {
+            // SAFETY:
+            // 1. We have checked that our table is allocated.
+            // 2. The caller ensures that `table_layout` matches the [`TableLayout`]
+            // that was used to allocate this table.
+            unsafe { self.allocation_info(table_layout) }
+        }
+    }
+
+    /// Marks all table buckets as empty without dropping their contents.
+    #[inline]
+    fn clear_no_drop(&mut self) {
+        if !self.is_empty_singleton() {
+            unsafe {
+                self.ctrl(0).write_bytes(EMPTY, self.num_ctrl_bytes());
+            }
+        }
+        self.items = 0;
+        self.growth_left = bucket_mask_to_capacity(self.bucket_mask);
+    }
+
+    /// Erases the [`Bucket`]'s control byte at the given index so that it does not
+    /// triggered as full, decreases the `items` of the table and, if it can be done,
+    /// increases `self.growth_left`.
+    ///
+    /// This function does not actually erase / drop the [`Bucket`] itself, i.e. it
+    /// does not make any changes to the `data` parts of the table. The caller of this
+    /// function must take care to properly drop the `data`, otherwise calling this
+    /// function may result in a memory leak.
+    ///
+    /// # Safety
+    ///
+    /// You must observe the following safety rules when calling this function:
+    ///
+    /// * The [`RawTableInner`] has already been allocated;
+    ///
+    /// * It must be the full control byte at the given position;
+    ///
+    /// * The `index` must not be greater than the `RawTableInner.bucket_mask`, i.e.
+    ///   `index <= RawTableInner.bucket_mask` or, in other words, `(index + 1)` must
+    ///   be no greater than the number returned by the function [`RawTableInner::buckets`].
+    ///
+    /// Calling this function on a table that has not been allocated results in [`undefined behavior`].
+    ///
+    /// Calling this function on a table with no elements is unspecified, but calling subsequent
+    /// functions is likely to result in [`undefined behavior`] due to overflow subtraction
+    /// (`self.items -= 1 cause overflow when self.items == 0`).
+    ///
+    /// See also [`Bucket::as_ptr`] method, for more information about of properly removing
+    /// or saving `data element` from / into the [`RawTable`] / [`RawTableInner`].
+    ///
+    /// [`RawTableInner::buckets`]: RawTableInner::buckets
+    /// [`Bucket::as_ptr`]: Bucket::as_ptr
+    /// [`undefined behavior`]: https://doc.rust-lang.org/reference/behavior-considered-undefined.html
+    #[inline]
+    unsafe fn erase(&mut self, index: usize) {
+        debug_assert!(self.is_bucket_full(index));
+
+        // This is the same as `index.wrapping_sub(Group::WIDTH) % self.buckets()` because
+        // the number of buckets is a power of two, and `self.bucket_mask = self.buckets() - 1`.
+        let index_before = index.wrapping_sub(Group::WIDTH) & self.bucket_mask;
+        // SAFETY:
+        // - The caller must uphold the safety contract for `erase` method;
+        // - `index_before` is guaranteed to be in range due to masking with `self.bucket_mask`
+        let empty_before = Group::load(self.ctrl(index_before)).match_empty();
+        let empty_after = Group::load(self.ctrl(index)).match_empty();
+
+        // Inserting and searching in the map is performed by two key functions:
+        //
+        // - The `find_insert_slot` function that looks up the index of any `EMPTY` or `DELETED`
+        //   slot in a group to be able to insert. If it doesn't find an `EMPTY` or `DELETED`
+        //   slot immediately in the first group, it jumps to the next `Group` looking for it,
+        //   and so on until it has gone through all the groups in the control bytes.
+        //
+        // - The `find_inner` function that looks for the index of the desired element by looking
+        //   at all the `FULL` bytes in the group. If it did not find the element right away, and
+        //   there is no `EMPTY` byte in the group, then this means that the `find_insert_slot`
+        //   function may have found a suitable slot in the next group. Therefore, `find_inner`
+        //   jumps further, and if it does not find the desired element and again there is no `EMPTY`
+        //   byte, then it jumps further, and so on. The search stops only if `find_inner` function
+        //   finds the desired element or hits an `EMPTY` slot/byte.
+        //
+        // Accordingly, this leads to two consequences:
+        //
+        // - The map must have `EMPTY` slots (bytes);
+        //
+        // - You can't just mark the byte to be erased as `EMPTY`, because otherwise the `find_inner`
+        //   function may stumble upon an `EMPTY` byte before finding the desired element and stop
+        //   searching.
+        //
+        // Thus it is necessary to check all bytes after and before the erased element. If we are in
+        // a contiguous `Group` of `FULL` or `DELETED` bytes (the number of `FULL` or `DELETED` bytes
+        // before and after is greater than or equal to `Group::WIDTH`), then we must mark our byte as
+        // `DELETED` in order for the `find_inner` function to go further. On the other hand, if there
+        // is at least one `EMPTY` slot in the `Group`, then the `find_inner` function will still stumble
+        // upon an `EMPTY` byte, so we can safely mark our erased byte as `EMPTY` as well.
+        //
+        // Finally, since `index_before == (index.wrapping_sub(Group::WIDTH) & self.bucket_mask) == index`
+        // and given all of the above, tables smaller than the group width (self.buckets() < Group::WIDTH)
+        // cannot have `DELETED` bytes.
+        //
+        // Note that in this context `leading_zeros` refers to the bytes at the end of a group, while
+        // `trailing_zeros` refers to the bytes at the beginning of a group.
+        let ctrl = if empty_before.leading_zeros() + empty_after.trailing_zeros() >= Group::WIDTH {
+            DELETED
+        } else {
+            self.growth_left += 1;
+            EMPTY
+        };
+        // SAFETY: the caller must uphold the safety contract for `erase` method.
+        self.set_ctrl(index, ctrl);
+        self.items -= 1;
+    }
+}
+
+impl<T: Clone, A: Allocator + Clone> Clone for RawTable<T, A> {
+    fn clone(&self) -> Self {
+        if self.table.is_empty_singleton() {
+            Self::new_in(self.alloc.clone())
+        } else {
+            unsafe {
+                // Avoid `Result::ok_or_else` because it bloats LLVM IR.
+                //
+                // SAFETY: This is safe as we are taking the size of an already allocated table
+                // and therefore сapacity overflow cannot occur, `self.table.buckets()` is power
+                // of two and all allocator errors will be caught inside `RawTableInner::new_uninitialized`.
+                let mut new_table = match Self::new_uninitialized(
+                    self.alloc.clone(),
+                    self.table.buckets(),
+                    Fallibility::Infallible,
+                ) {
+                    Ok(table) => table,
+                    Err(_) => hint::unreachable_unchecked(),
+                };
+
+                // Cloning elements may fail (the clone function may panic). But we don't
+                // need to worry about uninitialized control bits, since:
+                // 1. The number of items (elements) in the table is zero, which means that
+                //    the control bits will not be readed by Drop function.
+                // 2. The `clone_from_spec` method will first copy all control bits from
+                //    `self` (thus initializing them). But this will not affect the `Drop`
+                //    function, since the `clone_from_spec` function sets `items` only after
+                //    successfully clonning all elements.
+                new_table.clone_from_spec(self);
+                new_table
+            }
+        }
+    }
+
+    fn clone_from(&mut self, source: &Self) {
+        if source.table.is_empty_singleton() {
+            let mut old_inner = mem::replace(&mut self.table, RawTableInner::NEW);
+            unsafe {
+                // SAFETY:
+                // 1. We call the function only once;
+                // 2. We know for sure that `alloc` and `table_layout` matches the [`Allocator`]
+                //    and [`TableLayout`] that were used to allocate this table.
+                // 3. If any elements' drop function panics, then there will only be a memory leak,
+                //    because we have replaced the inner table with a new one.
+                old_inner.drop_inner_table::<T, _>(&self.alloc, Self::TABLE_LAYOUT);
+            }
+        } else {
+            unsafe {
+                // Make sure that if any panics occurs, we clear the table and
+                // leave it in an empty state.
+                let mut self_ = guard(self, |self_| {
+                    self_.clear_no_drop();
+                });
+
+                // First, drop all our elements without clearing the control
+                // bytes. If this panics then the scope guard will clear the
+                // table, leaking any elements that were not dropped yet.
+                //
+                // This leak is unavoidable: we can't try dropping more elements
+                // since this could lead to another panic and abort the process.
+                //
+                // SAFETY: If something gets wrong we clear our table right after
+                // dropping the elements, so there is no double drop, since `items`
+                // will be equal to zero.
+                self_.table.drop_elements::<T>();
+
+                // If necessary, resize our table to match the source.
+                if self_.buckets() != source.buckets() {
+                    let new_inner = match RawTableInner::new_uninitialized(
+                        &self_.alloc,
+                        Self::TABLE_LAYOUT,
+                        source.buckets(),
+                        Fallibility::Infallible,
+                    ) {
+                        Ok(table) => table,
+                        Err(_) => hint::unreachable_unchecked(),
+                    };
+                    // Replace the old inner with new uninitialized one. It's ok, since if something gets
+                    // wrong `ScopeGuard` will initialize all control bytes and leave empty table.
+                    let mut old_inner = mem::replace(&mut self_.table, new_inner);
+                    if !old_inner.is_empty_singleton() {
+                        // SAFETY:
+                        // 1. We have checked that our table is allocated.
+                        // 2. We know for sure that `alloc` and `table_layout` matches
+                        // the [`Allocator`] and [`TableLayout`] that were used to allocate this table.
+                        old_inner.free_buckets(&self_.alloc, Self::TABLE_LAYOUT);
+                    }
+                }
+
+                // Cloning elements may fail (the clone function may panic), but the `ScopeGuard`
+                // inside the `clone_from_impl` function will take care of that, dropping all
+                // cloned elements if necessary. Our `ScopeGuard` will clear the table.
+                self_.clone_from_spec(source);
+
+                // Disarm the scope guard if cloning was successful.
+                ScopeGuard::into_inner(self_);
+            }
+        }
+    }
+}
+
+/// Specialization of `clone_from` for `Copy` types
+trait RawTableClone {
+    unsafe fn clone_from_spec(&mut self, source: &Self);
+}
+impl<T: Clone, A: Allocator + Clone> RawTableClone for RawTable<T, A> {
+    default_fn! {
+        #[cfg_attr(feature = "inline-more", inline)]
+        unsafe fn clone_from_spec(&mut self, source: &Self) {
+            self.clone_from_impl(source);
+        }
+    }
+}
+#[cfg(feature = "nightly")]
+impl<T: Copy, A: Allocator + Clone> RawTableClone for RawTable<T, A> {
+    #[cfg_attr(feature = "inline-more", inline)]
+    unsafe fn clone_from_spec(&mut self, source: &Self) {
+        source
+            .table
+            .ctrl(0)
+            .copy_to_nonoverlapping(self.table.ctrl(0), self.table.num_ctrl_bytes());
+        source
+            .data_start()
+            .as_ptr()
+            .copy_to_nonoverlapping(self.data_start().as_ptr(), self.table.buckets());
+
+        self.table.items = source.table.items;
+        self.table.growth_left = source.table.growth_left;
+    }
+}
+
+impl<T: Clone, A: Allocator + Clone> RawTable<T, A> {
+    /// Common code for clone and clone_from. Assumes:
+    /// - `self.buckets() == source.buckets()`.
+    /// - Any existing elements have been dropped.
+    /// - The control bytes are not initialized yet.
+    #[cfg_attr(feature = "inline-more", inline)]
+    unsafe fn clone_from_impl(&mut self, source: &Self) {
+        // Copy the control bytes unchanged. We do this in a single pass
+        source
+            .table
+            .ctrl(0)
+            .copy_to_nonoverlapping(self.table.ctrl(0), self.table.num_ctrl_bytes());
+
+        // The cloning of elements may panic, in which case we need
+        // to make sure we drop only the elements that have been
+        // cloned so far.
+        let mut guard = guard((0, &mut *self), |(index, self_)| {
+            if T::NEEDS_DROP {
+                for i in 0..=*index {
+                    if self_.is_bucket_full(i) {
+                        self_.bucket(i).drop();
+                    }
+                }
+            }
+        });
+
+        for from in source.iter() {
+            let index = source.bucket_index(&from);
+            let to = guard.1.bucket(index);
+            to.write(from.as_ref().clone());
+
+            // Update the index in case we need to unwind.
+            guard.0 = index;
+        }
+
+        // Successfully cloned all items, no need to clean up.
+        mem::forget(guard);
+
+        self.table.items = source.table.items;
+        self.table.growth_left = source.table.growth_left;
+    }
+
+    /// Variant of `clone_from` to use when a hasher is available.
+    #[cfg(feature = "raw")]
+    pub fn clone_from_with_hasher(&mut self, source: &Self, hasher: impl Fn(&T) -> u64) {
+        // If we have enough capacity in the table, just clear it and insert
+        // elements one by one. We don't do this if we have the same number of
+        // buckets as the source since we can just copy the contents directly
+        // in that case.
+        if self.table.buckets() != source.table.buckets()
+            && bucket_mask_to_capacity(self.table.bucket_mask) >= source.len()
+        {
+            self.clear();
+
+            let mut guard_self = guard(&mut *self, |self_| {
+                // Clear the partially copied table if a panic occurs, otherwise
+                // items and growth_left will be out of sync with the contents
+                // of the table.
+                self_.clear();
+            });
+
+            unsafe {
+                for item in source.iter() {
+                    // This may panic.
+                    let item = item.as_ref().clone();
+                    let hash = hasher(&item);
+
+                    // We can use a simpler version of insert() here since:
+                    // - there are no DELETED entries.
+                    // - we know there is enough space in the table.
+                    // - all elements are unique.
+                    let (index, _) = guard_self.table.prepare_insert_slot(hash);
+                    guard_self.bucket(index).write(item);
+                }
+            }
+
+            // Successfully cloned all items, no need to clean up.
+            mem::forget(guard_self);
+
+            self.table.items = source.table.items;
+            self.table.growth_left -= source.table.items;
+        } else {
+            self.clone_from(source);
+        }
+    }
+}
+
+impl<T, A: Allocator + Default> Default for RawTable<T, A> {
+    #[inline]
+    fn default() -> Self {
+        Self::new_in(Default::default())
+    }
+}
+
+#[cfg(feature = "nightly")]
+unsafe impl<#[may_dangle] T, A: Allocator> Drop for RawTable<T, A> {
+    #[cfg_attr(feature = "inline-more", inline)]
+    fn drop(&mut self) {
+        unsafe {
+            // SAFETY:
+            // 1. We call the function only once;
+            // 2. We know for sure that `alloc` and `table_layout` matches the [`Allocator`]
+            //    and [`TableLayout`] that were used to allocate this table.
+            // 3. If the drop function of any elements fails, then only a memory leak will occur,
+            //    and we don't care because we are inside the `Drop` function of the `RawTable`,
+            //    so there won't be any table left in an inconsistent state.
+            self.table
+                .drop_inner_table::<T, _>(&self.alloc, Self::TABLE_LAYOUT);
+        }
+    }
+}
+#[cfg(not(feature = "nightly"))]
+impl<T, A: Allocator> Drop for RawTable<T, A> {
+    #[cfg_attr(feature = "inline-more", inline)]
+    fn drop(&mut self) {
+        unsafe {
+            // SAFETY:
+            // 1. We call the function only once;
+            // 2. We know for sure that `alloc` and `table_layout` matches the [`Allocator`]
+            //    and [`TableLayout`] that were used to allocate this table.
+            // 3. If the drop function of any elements fails, then only a memory leak will occur,
+            //    and we don't care because we are inside the `Drop` function of the `RawTable`,
+            //    so there won't be any table left in an inconsistent state.
+            self.table
+                .drop_inner_table::<T, _>(&self.alloc, Self::TABLE_LAYOUT);
+        }
+    }
+}
+
+impl<T, A: Allocator> IntoIterator for RawTable<T, A> {
+    type Item = T;
+    type IntoIter = RawIntoIter<T, A>;
+
+    #[cfg_attr(feature = "inline-more", inline)]
+    fn into_iter(self) -> RawIntoIter<T, A> {
+        unsafe {
+            let iter = self.iter();
+            self.into_iter_from(iter)
+        }
+    }
+}
+
+/// Iterator over a sub-range of a table. Unlike `RawIter` this iterator does
+/// not track an item count.
+pub(crate) struct RawIterRange<T> {
+    // Mask of full buckets in the current group. Bits are cleared from this
+    // mask as each element is processed.
+    current_group: BitMaskIter,
+
+    // Pointer to the buckets for the current group.
+    data: Bucket<T>,
+
+    // Pointer to the next group of control bytes,
+    // Must be aligned to the group size.
+    next_ctrl: *const u8,
+
+    // Pointer one past the last control byte of this range.
+    end: *const u8,
+}
+
+impl<T> RawIterRange<T> {
+    /// Returns a `RawIterRange` covering a subset of a table.
+    ///
+    /// # Safety
+    ///
+    /// If any of the following conditions are violated, the result is
+    /// [`undefined behavior`]:
+    ///
+    /// * `ctrl` must be [valid] for reads, i.e. table outlives the `RawIterRange`;
+    ///
+    /// * `ctrl` must be properly aligned to the group size (Group::WIDTH);
+    ///
+    /// * `ctrl` must point to the array of properly initialized control bytes;
+    ///
+    /// * `data` must be the [`Bucket`] at the `ctrl` index in the table;
+    ///
+    /// * the value of `len` must be less than or equal to the number of table buckets,
+    ///   and the returned value of `ctrl.as_ptr().add(len).offset_from(ctrl.as_ptr())`
+    ///   must be positive.
+    ///
+    /// * The `ctrl.add(len)` pointer must be either in bounds or one
+    ///   byte past the end of the same [allocated table].
+    ///
+    /// * The `len` must be a power of two.
+    ///
+    /// [`undefined behavior`]: https://doc.rust-lang.org/reference/behavior-considered-undefined.html
+    #[cfg_attr(feature = "inline-more", inline)]
+    unsafe fn new(ctrl: *const u8, data: Bucket<T>, len: usize) -> Self {
+        debug_assert_ne!(len, 0);
+        debug_assert_eq!(ctrl as usize % Group::WIDTH, 0);
+        // SAFETY: The caller must uphold the safety rules for the [`RawIterRange::new`]
+        let end = ctrl.add(len);
+
+        // Load the first group and advance ctrl to point to the next group
+        // SAFETY: The caller must uphold the safety rules for the [`RawIterRange::new`]
+        let current_group = Group::load_aligned(ctrl).match_full();
+        let next_ctrl = ctrl.add(Group::WIDTH);
+
+        Self {
+            current_group: current_group.into_iter(),
+            data,
+            next_ctrl,
+            end,
+        }
+    }
+
+    /// Splits a `RawIterRange` into two halves.
+    ///
+    /// Returns `None` if the remaining range is smaller than or equal to the
+    /// group width.
+    #[cfg_attr(feature = "inline-more", inline)]
+    #[cfg(feature = "rayon")]
+    pub(crate) fn split(mut self) -> (Self, Option<RawIterRange<T>>) {
+        unsafe {
+            if self.end <= self.next_ctrl {
+                // Nothing to split if the group that we are current processing
+                // is the last one.
+                (self, None)
+            } else {
+                // len is the remaining number of elements after the group that
+                // we are currently processing. It must be a multiple of the
+                // group size (small tables are caught by the check above).
+                let len = offset_from(self.end, self.next_ctrl);
+                debug_assert_eq!(len % Group::WIDTH, 0);
+
+                // Split the remaining elements into two halves, but round the
+                // midpoint down in case there is an odd number of groups
+                // remaining. This ensures that:
+                // - The tail is at least 1 group long.
+                // - The split is roughly even considering we still have the
+                //   current group to process.
+                let mid = (len / 2) & !(Group::WIDTH - 1);
+
+                let tail = Self::new(
+                    self.next_ctrl.add(mid),
+                    self.data.next_n(Group::WIDTH).next_n(mid),
+                    len - mid,
+                );
+                debug_assert_eq!(
+                    self.data.next_n(Group::WIDTH).next_n(mid).ptr,
+                    tail.data.ptr
+                );
+                debug_assert_eq!(self.end, tail.end);
+                self.end = self.next_ctrl.add(mid);
+                debug_assert_eq!(self.end.add(Group::WIDTH), tail.next_ctrl);
+                (self, Some(tail))
+            }
+        }
+    }
+
+    /// # Safety
+    /// If DO_CHECK_PTR_RANGE is false, caller must ensure that we never try to iterate
+    /// after yielding all elements.
+    #[cfg_attr(feature = "inline-more", inline)]
+    unsafe fn next_impl<const DO_CHECK_PTR_RANGE: bool>(&mut self) -> Option<Bucket<T>> {
+        loop {
+            if let Some(index) = self.current_group.next() {
+                return Some(self.data.next_n(index));
+            }
+
+            if DO_CHECK_PTR_RANGE && self.next_ctrl >= self.end {
+                return None;
+            }
+
+            // We might read past self.end up to the next group boundary,
+            // but this is fine because it only occurs on tables smaller
+            // than the group size where the trailing control bytes are all
+            // EMPTY. On larger tables self.end is guaranteed to be aligned
+            // to the group size (since tables are power-of-two sized).
+            self.current_group = Group::load_aligned(self.next_ctrl).match_full().into_iter();
+            self.data = self.data.next_n(Group::WIDTH);
+            self.next_ctrl = self.next_ctrl.add(Group::WIDTH);
+        }
+    }
+}
+
+// We make raw iterators unconditionally Send and Sync, and let the PhantomData
+// in the actual iterator implementations determine the real Send/Sync bounds.
+unsafe impl<T> Send for RawIterRange<T> {}
+unsafe impl<T> Sync for RawIterRange<T> {}
+
+impl<T> Clone for RawIterRange<T> {
+    #[cfg_attr(feature = "inline-more", inline)]
+    fn clone(&self) -> Self {
+        Self {
+            data: self.data.clone(),
+            next_ctrl: self.next_ctrl,
+            current_group: self.current_group,
+            end: self.end,
+        }
+    }
+}
+
+impl<T> Iterator for RawIterRange<T> {
+    type Item = Bucket<T>;
+
+    #[cfg_attr(feature = "inline-more", inline)]
+    fn next(&mut self) -> Option<Bucket<T>> {
+        unsafe {
+            // SAFETY: We set checker flag to true.
+            self.next_impl::<true>()
+        }
+    }
+
+    #[inline]
+    fn size_hint(&self) -> (usize, Option<usize>) {
+        // We don't have an item count, so just guess based on the range size.
+        let remaining_buckets = if self.end > self.next_ctrl {
+            unsafe { offset_from(self.end, self.next_ctrl) }
+        } else {
+            0
+        };
+
+        // Add a group width to include the group we are currently processing.
+        (0, Some(Group::WIDTH + remaining_buckets))
+    }
+}
+
+impl<T> FusedIterator for RawIterRange<T> {}
+
+/// Iterator which returns a raw pointer to every full bucket in the table.
+///
+/// For maximum flexibility this iterator is not bound by a lifetime, but you
+/// must observe several rules when using it:
+/// - You must not free the hash table while iterating (including via growing/shrinking).
+/// - It is fine to erase a bucket that has been yielded by the iterator.
+/// - Erasing a bucket that has not yet been yielded by the iterator may still
+///   result in the iterator yielding that bucket (unless `reflect_remove` is called).
+/// - It is unspecified whether an element inserted after the iterator was
+///   created will be yielded by that iterator (unless `reflect_insert` is called).
+/// - The order in which the iterator yields bucket is unspecified and may
+///   change in the future.
+pub struct RawIter<T> {
+    pub(crate) iter: RawIterRange<T>,
+    items: usize,
+}
+
+impl<T> RawIter<T> {
+    /// Refresh the iterator so that it reflects a removal from the given bucket.
+    ///
+    /// For the iterator to remain valid, this method must be called once
+    /// for each removed bucket before `next` is called again.
+    ///
+    /// This method should be called _before_ the removal is made. It is not necessary to call this
+    /// method if you are removing an item that this iterator yielded in the past.
+    #[cfg(feature = "raw")]
+    pub unsafe fn reflect_remove(&mut self, b: &Bucket<T>) {
+        self.reflect_toggle_full(b, false);
+    }
+
+    /// Refresh the iterator so that it reflects an insertion into the given bucket.
+    ///
+    /// For the iterator to remain valid, this method must be called once
+    /// for each insert before `next` is called again.
+    ///
+    /// This method does not guarantee that an insertion of a bucket with a greater
+    /// index than the last one yielded will be reflected in the iterator.
+    ///
+    /// This method should be called _after_ the given insert is made.
+    #[cfg(feature = "raw")]
+    pub unsafe fn reflect_insert(&mut self, b: &Bucket<T>) {
+        self.reflect_toggle_full(b, true);
+    }
+
+    /// Refresh the iterator so that it reflects a change to the state of the given bucket.
+    #[cfg(feature = "raw")]
+    unsafe fn reflect_toggle_full(&mut self, b: &Bucket<T>, is_insert: bool) {
+        if b.as_ptr() > self.iter.data.as_ptr() {
+            // The iterator has already passed the bucket's group.
+            // So the toggle isn't relevant to this iterator.
+            return;
+        }
+
+        if self.iter.next_ctrl < self.iter.end
+            && b.as_ptr() <= self.iter.data.next_n(Group::WIDTH).as_ptr()
+        {
+            // The iterator has not yet reached the bucket's group.
+            // We don't need to reload anything, but we do need to adjust the item count.
+
+            if cfg!(debug_assertions) {
+                // Double-check that the user isn't lying to us by checking the bucket state.
+                // To do that, we need to find its control byte. We know that self.iter.data is
+                // at self.iter.next_ctrl - Group::WIDTH, so we work from there:
+                let offset = offset_from(self.iter.data.as_ptr(), b.as_ptr());
+                let ctrl = self.iter.next_ctrl.sub(Group::WIDTH).add(offset);
+                // This method should be called _before_ a removal, or _after_ an insert,
+                // so in both cases the ctrl byte should indicate that the bucket is full.
+                assert!(is_full(*ctrl));
+            }
+
+            if is_insert {
+                self.items += 1;
+            } else {
+                self.items -= 1;
+            }
+
+            return;
+        }
+
+        // The iterator is at the bucket group that the toggled bucket is in.
+        // We need to do two things:
+        //
+        //  - Determine if the iterator already yielded the toggled bucket.
+        //    If it did, we're done.
+        //  - Otherwise, update the iterator cached group so that it won't
+        //    yield a to-be-removed bucket, or _will_ yield a to-be-added bucket.
+        //    We'll also need to update the item count accordingly.
+        if let Some(index) = self.iter.current_group.0.lowest_set_bit() {
+            let next_bucket = self.iter.data.next_n(index);
+            if b.as_ptr() > next_bucket.as_ptr() {
+                // The toggled bucket is "before" the bucket the iterator would yield next. We
+                // therefore don't need to do anything --- the iterator has already passed the
+                // bucket in question.
+                //
+                // The item count must already be correct, since a removal or insert "prior" to
+                // the iterator's position wouldn't affect the item count.
+            } else {
+                // The removed bucket is an upcoming bucket. We need to make sure it does _not_
+                // get yielded, and also that it's no longer included in the item count.
+                //
+                // NOTE: We can't just reload the group here, both since that might reflect
+                // inserts we've already passed, and because that might inadvertently unset the
+                // bits for _other_ removals. If we do that, we'd have to also decrement the
+                // item count for those other bits that we unset. But the presumably subsequent
+                // call to reflect for those buckets might _also_ decrement the item count.
+                // Instead, we _just_ flip the bit for the particular bucket the caller asked
+                // us to reflect.
+                let our_bit = offset_from(self.iter.data.as_ptr(), b.as_ptr());
+                let was_full = self.iter.current_group.flip(our_bit);
+                debug_assert_ne!(was_full, is_insert);
+
+                if is_insert {
+                    self.items += 1;
+                } else {
+                    self.items -= 1;
+                }
+
+                if cfg!(debug_assertions) {
+                    if b.as_ptr() == next_bucket.as_ptr() {
+                        // The removed bucket should no longer be next
+                        debug_assert_ne!(self.iter.current_group.0.lowest_set_bit(), Some(index));
+                    } else {
+                        // We should not have changed what bucket comes next.
+                        debug_assert_eq!(self.iter.current_group.0.lowest_set_bit(), Some(index));
+                    }
+                }
+            }
+        } else {
+            // We must have already iterated past the removed item.
+        }
+    }
+
+    unsafe fn drop_elements(&mut self) {
+        if T::NEEDS_DROP && self.items != 0 {
+            for item in self {
+                item.drop();
+            }
+        }
+    }
+}
+
+impl<T> Clone for RawIter<T> {
+    #[cfg_attr(feature = "inline-more", inline)]
+    fn clone(&self) -> Self {
+        Self {
+            iter: self.iter.clone(),
+            items: self.items,
+        }
+    }
+}
+
+impl<T> Iterator for RawIter<T> {
+    type Item = Bucket<T>;
+
+    #[cfg_attr(feature = "inline-more", inline)]
+    fn next(&mut self) -> Option<Bucket<T>> {
+        // Inner iterator iterates over buckets
+        // so it can do unnecessary work if we already yielded all items.
+        if self.items == 0 {
+            return None;
+        }
+
+        let nxt = unsafe {
+            // SAFETY: We check number of items to yield using `items` field.
+            self.iter.next_impl::<false>()
+        };
+
+        debug_assert!(nxt.is_some());
+        self.items -= 1;
+
+        nxt
+    }
+
+    #[inline]
+    fn size_hint(&self) -> (usize, Option<usize>) {
+        (self.items, Some(self.items))
+    }
+}
+
+impl<T> ExactSizeIterator for RawIter<T> {}
+impl<T> FusedIterator for RawIter<T> {}
+
+/// Iterator which returns an index of every full bucket in the table.
+///
+/// For maximum flexibility this iterator is not bound by a lifetime, but you
+/// must observe several rules when using it:
+/// - You must not free the hash table while iterating (including via growing/shrinking).
+/// - It is fine to erase a bucket that has been yielded by the iterator.
+/// - Erasing a bucket that has not yet been yielded by the iterator may still
+///   result in the iterator yielding index of that bucket.
+/// - It is unspecified whether an element inserted after the iterator was
+///   created will be yielded by that iterator.
+/// - The order in which the iterator yields indices of the buckets is unspecified
+///   and may change in the future.
+pub(crate) struct FullBucketsIndices {
+    // Mask of full buckets in the current group. Bits are cleared from this
+    // mask as each element is processed.
+    current_group: BitMaskIter,
+
+    // Initial value of the bytes' indices of the current group (relative
+    // to the start of the control bytes).
+    group_first_index: usize,
+
+    // Pointer to the current group of control bytes,
+    // Must be aligned to the group size (Group::WIDTH).
+    ctrl: NonNull<u8>,
+
+    // Number of elements in the table.
+    items: usize,
+}
+
+impl FullBucketsIndices {
+    /// Advances the iterator and returns the next value.
+    ///
+    /// # Safety
+    ///
+    /// If any of the following conditions are violated, the result is
+    /// [`Undefined Behavior`]:
+    ///
+    /// * The [`RawTableInner`] / [`RawTable`] must be alive and not moved,
+    ///   i.e. table outlives the `FullBucketsIndices`;
+    ///
+    /// * It never tries to iterate after getting all elements.
+    ///
+    /// [`Undefined Behavior`]: https://doc.rust-lang.org/reference/behavior-considered-undefined.html
+    #[inline(always)]
+    unsafe fn next_impl(&mut self) -> Option<usize> {
+        loop {
+            if let Some(index) = self.current_group.next() {
+                // The returned `self.group_first_index + index` will always
+                // be in the range `0..self.buckets()`. See explanation below.
+                return Some(self.group_first_index + index);
+            }
+
+            // SAFETY: The caller of this function ensures that:
+            //
+            // 1. It never tries to iterate after getting all the elements;
+            // 2. The table is alive and did not moved;
+            // 3. The first `self.ctrl` pointed to the start of the array of control bytes.
+            //
+            // Taking the above into account, we always stay within the bounds, because:
+            //
+            // 1. For tables smaller than the group width (self.buckets() <= Group::WIDTH),
+            //    we will never end up in the given branch, since we should have already
+            //    yielded all the elements of the table.
+            //
+            // 2. For tables larger than the group width. The the number of buckets is a
+            //    power of two (2 ^ n), Group::WIDTH is also power of two (2 ^ k). Sinse
+            //    `(2 ^ n) > (2 ^ k)`, than `(2 ^ n) % (2 ^ k) = 0`. As we start from the
+            //    the start of the array of control bytes, and never try to iterate after
+            //    getting all the elements, the last `self.ctrl` will be equal to
+            //    the `self.buckets() - Group::WIDTH`, so `self.current_group.next()`
+            //    will always contains indices within the range `0..Group::WIDTH`,
+            //    and subsequent `self.group_first_index + index` will always return a
+            //    number less than `self.buckets()`.
+            self.ctrl = NonNull::new_unchecked(self.ctrl.as_ptr().add(Group::WIDTH));
+
+            // SAFETY: See explanation above.
+            self.current_group = Group::load_aligned(self.ctrl.as_ptr())
+                .match_full()
+                .into_iter();
+            self.group_first_index += Group::WIDTH;
+        }
+    }
+}
+
+impl Iterator for FullBucketsIndices {
+    type Item = usize;
+
+    /// Advances the iterator and returns the next value. It is up to
+    /// the caller to ensure that the `RawTable` outlives the `FullBucketsIndices`,
+    /// because we cannot make the `next` method unsafe.
+    #[inline(always)]
+    fn next(&mut self) -> Option<usize> {
+        // Return if we already yielded all items.
+        if self.items == 0 {
+            return None;
+        }
+
+        let nxt = unsafe {
+            // SAFETY:
+            // 1. We check number of items to yield using `items` field.
+            // 2. The caller ensures that the table is alive and has not moved.
+            self.next_impl()
+        };
+
+        debug_assert!(nxt.is_some());
+        self.items -= 1;
+
+        nxt
+    }
+
+    #[inline(always)]
+    fn size_hint(&self) -> (usize, Option<usize>) {
+        (self.items, Some(self.items))
+    }
+}
+
+impl ExactSizeIterator for FullBucketsIndices {}
+impl FusedIterator for FullBucketsIndices {}
+
+/// Iterator which consumes a table and returns elements.
+pub struct RawIntoIter<T, A: Allocator = Global> {
+    iter: RawIter<T>,
+    allocation: Option<(NonNull<u8>, Layout, A)>,
+    marker: PhantomData<T>,
+}
+
+impl<T, A: Allocator> RawIntoIter<T, A> {
+    #[cfg_attr(feature = "inline-more", inline)]
+    pub fn iter(&self) -> RawIter<T> {
+        self.iter.clone()
+    }
+}
+
+unsafe impl<T, A: Allocator> Send for RawIntoIter<T, A>
+where
+    T: Send,
+    A: Send,
+{
+}
+unsafe impl<T, A: Allocator> Sync for RawIntoIter<T, A>
+where
+    T: Sync,
+    A: Sync,
+{
+}
+
+#[cfg(feature = "nightly")]
+unsafe impl<#[may_dangle] T, A: Allocator> Drop for RawIntoIter<T, A> {
+    #[cfg_attr(feature = "inline-more", inline)]
+    fn drop(&mut self) {
+        unsafe {
+            // Drop all remaining elements
+            self.iter.drop_elements();
+
+            // Free the table
+            if let Some((ptr, layout, ref alloc)) = self.allocation {
+                alloc.deallocate(ptr, layout);
+            }
+        }
+    }
+}
+#[cfg(not(feature = "nightly"))]
+impl<T, A: Allocator> Drop for RawIntoIter<T, A> {
+    #[cfg_attr(feature = "inline-more", inline)]
+    fn drop(&mut self) {
+        unsafe {
+            // Drop all remaining elements
+            self.iter.drop_elements();
+
+            // Free the table
+            if let Some((ptr, layout, ref alloc)) = self.allocation {
+                alloc.deallocate(ptr, layout);
+            }
+        }
+    }
+}
+
+impl<T, A: Allocator> Iterator for RawIntoIter<T, A> {
+    type Item = T;
+
+    #[cfg_attr(feature = "inline-more", inline)]
+    fn next(&mut self) -> Option<T> {
+        unsafe { Some(self.iter.next()?.read()) }
+    }
+
+    #[inline]
+    fn size_hint(&self) -> (usize, Option<usize>) {
+        self.iter.size_hint()
+    }
+}
+
+impl<T, A: Allocator> ExactSizeIterator for RawIntoIter<T, A> {}
+impl<T, A: Allocator> FusedIterator for RawIntoIter<T, A> {}
+
+/// Iterator which consumes elements without freeing the table storage.
+pub struct RawDrain<'a, T, A: Allocator = Global> {
+    iter: RawIter<T>,
+
+    // The table is moved into the iterator for the duration of the drain. This
+    // ensures that an empty table is left if the drain iterator is leaked
+    // without dropping.
+    table: RawTableInner,
+    orig_table: NonNull<RawTableInner>,
+
+    // We don't use a &'a mut RawTable<T> because we want RawDrain to be
+    // covariant over T.
+    marker: PhantomData<&'a RawTable<T, A>>,
+}
+
+impl<T, A: Allocator> RawDrain<'_, T, A> {
+    #[cfg_attr(feature = "inline-more", inline)]
+    pub fn iter(&self) -> RawIter<T> {
+        self.iter.clone()
+    }
+}
+
+unsafe impl<T, A: Allocator> Send for RawDrain<'_, T, A>
+where
+    T: Send,
+    A: Send,
+{
+}
+unsafe impl<T, A: Allocator> Sync for RawDrain<'_, T, A>
+where
+    T: Sync,
+    A: Sync,
+{
+}
+
+impl<T, A: Allocator> Drop for RawDrain<'_, T, A> {
+    #[cfg_attr(feature = "inline-more", inline)]
+    fn drop(&mut self) {
+        unsafe {
+            // Drop all remaining elements. Note that this may panic.
+            self.iter.drop_elements();
+
+            // Reset the contents of the table now that all elements have been
+            // dropped.
+            self.table.clear_no_drop();
+
+            // Move the now empty table back to its original location.
+            self.orig_table
+                .as_ptr()
+                .copy_from_nonoverlapping(&self.table, 1);
+        }
+    }
+}
+
+impl<T, A: Allocator> Iterator for RawDrain<'_, T, A> {
+    type Item = T;
+
+    #[cfg_attr(feature = "inline-more", inline)]
+    fn next(&mut self) -> Option<T> {
+        unsafe {
+            let item = self.iter.next()?;
+            Some(item.read())
+        }
+    }
+
+    #[inline]
+    fn size_hint(&self) -> (usize, Option<usize>) {
+        self.iter.size_hint()
+    }
+}
+
+impl<T, A: Allocator> ExactSizeIterator for RawDrain<'_, T, A> {}
+impl<T, A: Allocator> FusedIterator for RawDrain<'_, T, A> {}
+
+/// Iterator over occupied buckets that could match a given hash.
+///
+/// `RawTable` only stores 7 bits of the hash value, so this iterator may return
+/// items that have a hash value different than the one provided. You should
+/// always validate the returned values before using them.
+///
+/// For maximum flexibility this iterator is not bound by a lifetime, but you
+/// must observe several rules when using it:
+/// - You must not free the hash table while iterating (including via growing/shrinking).
+/// - It is fine to erase a bucket that has been yielded by the iterator.
+/// - Erasing a bucket that has not yet been yielded by the iterator may still
+///   result in the iterator yielding that bucket.
+/// - It is unspecified whether an element inserted after the iterator was
+///   created will be yielded by that iterator.
+/// - The order in which the iterator yields buckets is unspecified and may
+///   change in the future.
+pub struct RawIterHash<T> {
+    inner: RawIterHashInner,
+    _marker: PhantomData<T>,
+}
+
+struct RawIterHashInner {
+    // See `RawTableInner`'s corresponding fields for details.
+    // We can't store a `*const RawTableInner` as it would get
+    // invalidated by the user calling `&mut` methods on `RawTable`.
+    bucket_mask: usize,
+    ctrl: NonNull<u8>,
+
+    // The top 7 bits of the hash.
+    h2_hash: u8,
+
+    // The sequence of groups to probe in the search.
+    probe_seq: ProbeSeq,
+
+    group: Group,
+
+    // The elements within the group with a matching h2-hash.
+    bitmask: BitMaskIter,
+}
+
+impl<T> RawIterHash<T> {
+    #[cfg_attr(feature = "inline-more", inline)]
+    #[cfg(feature = "raw")]
+    unsafe fn new<A: Allocator>(table: &RawTable<T, A>, hash: u64) -> Self {
+        RawIterHash {
+            inner: RawIterHashInner::new(&table.table, hash),
+            _marker: PhantomData,
+        }
+    }
+}
+impl RawIterHashInner {
+    #[cfg_attr(feature = "inline-more", inline)]
+    #[cfg(feature = "raw")]
+    unsafe fn new(table: &RawTableInner, hash: u64) -> Self {
+        let h2_hash = h2(hash);
+        let probe_seq = table.probe_seq(hash);
+        let group = Group::load(table.ctrl(probe_seq.pos));
+        let bitmask = group.match_byte(h2_hash).into_iter();
+
+        RawIterHashInner {
+            bucket_mask: table.bucket_mask,
+            ctrl: table.ctrl,
+            h2_hash,
+            probe_seq,
+            group,
+            bitmask,
+        }
+    }
+}
+
+impl<T> Iterator for RawIterHash<T> {
+    type Item = Bucket<T>;
+
+    fn next(&mut self) -> Option<Bucket<T>> {
+        unsafe {
+            match self.inner.next() {
+                Some(index) => {
+                    // Can't use `RawTable::bucket` here as we don't have
+                    // an actual `RawTable` reference to use.
+                    debug_assert!(index <= self.inner.bucket_mask);
+                    let bucket = Bucket::from_base_index(self.inner.ctrl.cast(), index);
+                    Some(bucket)
+                }
+                None => None,
+            }
+        }
+    }
+}
+
+impl Iterator for RawIterHashInner {
+    type Item = usize;
+
+    fn next(&mut self) -> Option<Self::Item> {
+        unsafe {
+            loop {
+                if let Some(bit) = self.bitmask.next() {
+                    let index = (self.probe_seq.pos + bit) & self.bucket_mask;
+                    return Some(index);
+                }
+                if likely(self.group.match_empty().any_bit_set()) {
+                    return None;
+                }
+                self.probe_seq.move_next(self.bucket_mask);
+
+                // Can't use `RawTableInner::ctrl` here as we don't have
+                // an actual `RawTableInner` reference to use.
+                let index = self.probe_seq.pos;
+                debug_assert!(index < self.bucket_mask + 1 + Group::WIDTH);
+                let group_ctrl = self.ctrl.as_ptr().add(index);
+
+                self.group = Group::load(group_ctrl);
+                self.bitmask = self.group.match_byte(self.h2_hash).into_iter();
+            }
+        }
+    }
+}
+
+#[cfg(test)]
+mod test_map {
+    use super::*;
+
+    fn rehash_in_place<T>(table: &mut RawTable<T>, hasher: impl Fn(&T) -> u64) {
+        unsafe {
+            table.table.rehash_in_place(
+                &|table, index| hasher(table.bucket::<T>(index).as_ref()),
+                mem::size_of::<T>(),
+                if mem::needs_drop::<T>() {
+                    Some(mem::transmute(ptr::drop_in_place::<T> as unsafe fn(*mut T)))
+                } else {
+                    None
+                },
+            );
+        }
+    }
+
+    #[test]
+    fn rehash() {
+        let mut table = RawTable::new();
+        let hasher = |i: &u64| *i;
+        for i in 0..100 {
+            table.insert(i, i, hasher);
+        }
+
+        for i in 0..100 {
+            unsafe {
+                assert_eq!(table.find(i, |x| *x == i).map(|b| b.read()), Some(i));
+            }
+            assert!(table.find(i + 100, |x| *x == i + 100).is_none());
+        }
+
+        rehash_in_place(&mut table, hasher);
+
+        for i in 0..100 {
+            unsafe {
+                assert_eq!(table.find(i, |x| *x == i).map(|b| b.read()), Some(i));
+            }
+            assert!(table.find(i + 100, |x| *x == i + 100).is_none());
+        }
+    }
+
+    /// CHECKING THAT WE ARE NOT TRYING TO READ THE MEMORY OF
+    /// AN UNINITIALIZED TABLE DURING THE DROP
+    #[test]
+    fn test_drop_uninitialized() {
+        use ::alloc::vec::Vec;
+
+        let table = unsafe {
+            // SAFETY: The `buckets` is power of two and we're not
+            // trying to actually use the returned RawTable.
+            RawTable::<(u64, Vec<i32>)>::new_uninitialized(Global, 8, Fallibility::Infallible)
+                .unwrap()
+        };
+        drop(table);
+    }
+
+    /// CHECKING THAT WE DON'T TRY TO DROP DATA IF THE `ITEMS`
+    /// ARE ZERO, EVEN IF WE HAVE `FULL` CONTROL BYTES.
+    #[test]
+    fn test_drop_zero_items() {
+        use ::alloc::vec::Vec;
+        unsafe {
+            // SAFETY: The `buckets` is power of two and we're not
+            // trying to actually use the returned RawTable.
+            let table =
+                RawTable::<(u64, Vec<i32>)>::new_uninitialized(Global, 8, Fallibility::Infallible)
+                    .unwrap();
+
+            // WE SIMULATE, AS IT WERE, A FULL TABLE.
+
+            // SAFETY: We checked that the table is allocated and therefore the table already has
+            // `self.bucket_mask + 1 + Group::WIDTH` number of control bytes (see TableLayout::calculate_layout_for)
+            // so writing `table.table.num_ctrl_bytes() == bucket_mask + 1 + Group::WIDTH` bytes is safe.
+            table
+                .table
+                .ctrl(0)
+                .write_bytes(EMPTY, table.table.num_ctrl_bytes());
+
+            // SAFETY: table.capacity() is guaranteed to be smaller than table.buckets()
+            table.table.ctrl(0).write_bytes(0, table.capacity());
+
+            // Fix up the trailing control bytes. See the comments in set_ctrl
+            // for the handling of tables smaller than the group width.
+            if table.buckets() < Group::WIDTH {
+                // SAFETY: We have `self.bucket_mask + 1 + Group::WIDTH` number of control bytes,
+                // so copying `self.buckets() == self.bucket_mask + 1` bytes with offset equal to
+                // `Group::WIDTH` is safe
+                table
+                    .table
+                    .ctrl(0)
+                    .copy_to(table.table.ctrl(Group::WIDTH), table.table.buckets());
+            } else {
+                // SAFETY: We have `self.bucket_mask + 1 + Group::WIDTH` number of
+                // control bytes,so copying `Group::WIDTH` bytes with offset equal
+                // to `self.buckets() == self.bucket_mask + 1` is safe
+                table
+                    .table
+                    .ctrl(0)
+                    .copy_to(table.table.ctrl(table.table.buckets()), Group::WIDTH);
+            }
+            drop(table);
+        }
+    }
+
+    /// CHECKING THAT WE DON'T TRY TO DROP DATA IF THE `ITEMS`
+    /// ARE ZERO, EVEN IF WE HAVE `FULL` CONTROL BYTES.
+    #[test]
+    fn test_catch_panic_clone_from() {
+        use ::alloc::sync::Arc;
+        use ::alloc::vec::Vec;
+        use allocator_api2::alloc::{AllocError, Allocator, Global};
+        use core::sync::atomic::{AtomicI8, Ordering};
+        use std::thread;
+
+        struct MyAllocInner {
+            drop_count: Arc<AtomicI8>,
+        }
+
+        #[derive(Clone)]
+        struct MyAlloc {
+            _inner: Arc<MyAllocInner>,
+        }
+
+        impl Drop for MyAllocInner {
+            fn drop(&mut self) {
+                println!("MyAlloc freed.");
+                self.drop_count.fetch_sub(1, Ordering::SeqCst);
+            }
+        }
+
+        unsafe impl Allocator for MyAlloc {
+            fn allocate(&self, layout: Layout) -> std::result::Result<NonNull<[u8]>, AllocError> {
+                let g = Global;
+                g.allocate(layout)
+            }
+
+            unsafe fn deallocate(&self, ptr: NonNull<u8>, layout: Layout) {
+                let g = Global;
+                g.deallocate(ptr, layout)
+            }
+        }
+
+        const DISARMED: bool = false;
+        const ARMED: bool = true;
+
+        struct CheckedCloneDrop {
+            panic_in_clone: bool,
+            dropped: bool,
+            need_drop: Vec<u64>,
+        }
+
+        impl Clone for CheckedCloneDrop {
+            fn clone(&self) -> Self {
+                if self.panic_in_clone {
+                    panic!("panic in clone")
+                }
+                Self {
+                    panic_in_clone: self.panic_in_clone,
+                    dropped: self.dropped,
+                    need_drop: self.need_drop.clone(),
+                }
+            }
+        }
+
+        impl Drop for CheckedCloneDrop {
+            fn drop(&mut self) {
+                if self.dropped {
+                    panic!("double drop");
+                }
+                self.dropped = true;
+            }
+        }
+
+        let dropped: Arc<AtomicI8> = Arc::new(AtomicI8::new(2));
+
+        let mut table = RawTable::new_in(MyAlloc {
+            _inner: Arc::new(MyAllocInner {
+                drop_count: dropped.clone(),
+            }),
+        });
+
+        for (idx, panic_in_clone) in core::iter::repeat(DISARMED).take(7).enumerate() {
+            let idx = idx as u64;
+            table.insert(
+                idx,
+                (
+                    idx,
+                    CheckedCloneDrop {
+                        panic_in_clone,
+                        dropped: false,
+                        need_drop: vec![idx],
+                    },
+                ),
+                |(k, _)| *k,
+            );
+        }
+
+        assert_eq!(table.len(), 7);
+
+        thread::scope(|s| {
+            let result = s.spawn(|| {
+                let armed_flags = [
+                    DISARMED, DISARMED, ARMED, DISARMED, DISARMED, DISARMED, DISARMED,
+                ];
+                let mut scope_table = RawTable::new_in(MyAlloc {
+                    _inner: Arc::new(MyAllocInner {
+                        drop_count: dropped.clone(),
+                    }),
+                });
+                for (idx, &panic_in_clone) in armed_flags.iter().enumerate() {
+                    let idx = idx as u64;
+                    scope_table.insert(
+                        idx,
+                        (
+                            idx,
+                            CheckedCloneDrop {
+                                panic_in_clone,
+                                dropped: false,
+                                need_drop: vec![idx + 100],
+                            },
+                        ),
+                        |(k, _)| *k,
+                    );
+                }
+                table.clone_from(&scope_table);
+            });
+            assert!(result.join().is_err());
+        });
+
+        // Let's check that all iterators work fine and do not return elements
+        // (especially `RawIterRange`, which does not depend on the number of
+        // elements in the table, but looks directly at the control bytes)
+        //
+        // SAFETY: We know for sure that `RawTable` will outlive
+        // the returned `RawIter / RawIterRange` iterator.
+        assert_eq!(table.len(), 0);
+        assert_eq!(unsafe { table.iter().count() }, 0);
+        assert_eq!(unsafe { table.iter().iter.count() }, 0);
+
+        for idx in 0..table.buckets() {
+            let idx = idx as u64;
+            assert!(
+                table.find(idx, |(k, _)| *k == idx).is_none(),
+                "Index: {idx}"
+            );
+        }
+
+        // All allocator clones should already be dropped.
+        assert_eq!(dropped.load(Ordering::SeqCst), 1);
+    }
+}
diff --git a/vendor/hashbrown/src/raw/neon.rs b/vendor/hashbrown/src/raw/neon.rs
new file mode 100644
index 0000000..44e82d5
--- /dev/null
+++ b/vendor/hashbrown/src/raw/neon.rs
@@ -0,0 +1,124 @@
+use super::bitmask::BitMask;
+use super::EMPTY;
+use core::arch::aarch64 as neon;
+use core::mem;
+use core::num::NonZeroU64;
+
+pub(crate) type BitMaskWord = u64;
+pub(crate) type NonZeroBitMaskWord = NonZeroU64;
+pub(crate) const BITMASK_STRIDE: usize = 8;
+pub(crate) const BITMASK_MASK: BitMaskWord = !0;
+pub(crate) const BITMASK_ITER_MASK: BitMaskWord = 0x8080_8080_8080_8080;
+
+/// Abstraction over a group of control bytes which can be scanned in
+/// parallel.
+///
+/// This implementation uses a 64-bit NEON value.
+#[derive(Copy, Clone)]
+pub(crate) struct Group(neon::uint8x8_t);
+
+#[allow(clippy::use_self)]
+impl Group {
+    /// Number of bytes in the group.
+    pub(crate) const WIDTH: usize = mem::size_of::<Self>();
+
+    /// Returns a full group of empty bytes, suitable for use as the initial
+    /// value for an empty hash table.
+    ///
+    /// This is guaranteed to be aligned to the group size.
+    #[inline]
+    pub(crate) const fn static_empty() -> &'static [u8; Group::WIDTH] {
+        #[repr(C)]
+        struct AlignedBytes {
+            _align: [Group; 0],
+            bytes: [u8; Group::WIDTH],
+        }
+        const ALIGNED_BYTES: AlignedBytes = AlignedBytes {
+            _align: [],
+            bytes: [EMPTY; Group::WIDTH],
+        };
+        &ALIGNED_BYTES.bytes
+    }
+
+    /// Loads a group of bytes starting at the given address.
+    #[inline]
+    #[allow(clippy::cast_ptr_alignment)] // unaligned load
+    pub(crate) unsafe fn load(ptr: *const u8) -> Self {
+        Group(neon::vld1_u8(ptr))
+    }
+
+    /// Loads a group of bytes starting at the given address, which must be
+    /// aligned to `mem::align_of::<Group>()`.
+    #[inline]
+    #[allow(clippy::cast_ptr_alignment)]
+    pub(crate) unsafe fn load_aligned(ptr: *const u8) -> Self {
+        // FIXME: use align_offset once it stabilizes
+        debug_assert_eq!(ptr as usize & (mem::align_of::<Self>() - 1), 0);
+        Group(neon::vld1_u8(ptr))
+    }
+
+    /// Stores the group of bytes to the given address, which must be
+    /// aligned to `mem::align_of::<Group>()`.
+    #[inline]
+    #[allow(clippy::cast_ptr_alignment)]
+    pub(crate) unsafe fn store_aligned(self, ptr: *mut u8) {
+        // FIXME: use align_offset once it stabilizes
+        debug_assert_eq!(ptr as usize & (mem::align_of::<Self>() - 1), 0);
+        neon::vst1_u8(ptr, self.0);
+    }
+
+    /// Returns a `BitMask` indicating all bytes in the group which *may*
+    /// have the given value.
+    #[inline]
+    pub(crate) fn match_byte(self, byte: u8) -> BitMask {
+        unsafe {
+            let cmp = neon::vceq_u8(self.0, neon::vdup_n_u8(byte));
+            BitMask(neon::vget_lane_u64(neon::vreinterpret_u64_u8(cmp), 0))
+        }
+    }
+
+    /// Returns a `BitMask` indicating all bytes in the group which are
+    /// `EMPTY`.
+    #[inline]
+    pub(crate) fn match_empty(self) -> BitMask {
+        self.match_byte(EMPTY)
+    }
+
+    /// Returns a `BitMask` indicating all bytes in the group which are
+    /// `EMPTY` or `DELETED`.
+    #[inline]
+    pub(crate) fn match_empty_or_deleted(self) -> BitMask {
+        unsafe {
+            let cmp = neon::vcltz_s8(neon::vreinterpret_s8_u8(self.0));
+            BitMask(neon::vget_lane_u64(neon::vreinterpret_u64_u8(cmp), 0))
+        }
+    }
+
+    /// Returns a `BitMask` indicating all bytes in the group which are full.
+    #[inline]
+    pub(crate) fn match_full(self) -> BitMask {
+        unsafe {
+            let cmp = neon::vcgez_s8(neon::vreinterpret_s8_u8(self.0));
+            BitMask(neon::vget_lane_u64(neon::vreinterpret_u64_u8(cmp), 0))
+        }
+    }
+
+    /// Performs the following transformation on all bytes in the group:
+    /// - `EMPTY => EMPTY`
+    /// - `DELETED => EMPTY`
+    /// - `FULL => DELETED`
+    #[inline]
+    pub(crate) fn convert_special_to_empty_and_full_to_deleted(self) -> Self {
+        // Map high_bit = 1 (EMPTY or DELETED) to 1111_1111
+        // and high_bit = 0 (FULL) to 1000_0000
+        //
+        // Here's this logic expanded to concrete values:
+        //   let special = 0 > byte = 1111_1111 (true) or 0000_0000 (false)
+        //   1111_1111 | 1000_0000 = 1111_1111
+        //   0000_0000 | 1000_0000 = 1000_0000
+        unsafe {
+            let special = neon::vcltz_s8(neon::vreinterpret_s8_u8(self.0));
+            Group(neon::vorr_u8(special, neon::vdup_n_u8(0x80)))
+        }
+    }
+}
diff --git a/vendor/hashbrown/src/raw/sse2.rs b/vendor/hashbrown/src/raw/sse2.rs
new file mode 100644
index 0000000..956ba5d
--- /dev/null
+++ b/vendor/hashbrown/src/raw/sse2.rs
@@ -0,0 +1,149 @@
+use super::bitmask::BitMask;
+use super::EMPTY;
+use core::mem;
+use core::num::NonZeroU16;
+
+#[cfg(target_arch = "x86")]
+use core::arch::x86;
+#[cfg(target_arch = "x86_64")]
+use core::arch::x86_64 as x86;
+
+pub(crate) type BitMaskWord = u16;
+pub(crate) type NonZeroBitMaskWord = NonZeroU16;
+pub(crate) const BITMASK_STRIDE: usize = 1;
+pub(crate) const BITMASK_MASK: BitMaskWord = 0xffff;
+pub(crate) const BITMASK_ITER_MASK: BitMaskWord = !0;
+
+/// Abstraction over a group of control bytes which can be scanned in
+/// parallel.
+///
+/// This implementation uses a 128-bit SSE value.
+#[derive(Copy, Clone)]
+pub(crate) struct Group(x86::__m128i);
+
+// FIXME: https://github.com/rust-lang/rust-clippy/issues/3859
+#[allow(clippy::use_self)]
+impl Group {
+    /// Number of bytes in the group.
+    pub(crate) const WIDTH: usize = mem::size_of::<Self>();
+
+    /// Returns a full group of empty bytes, suitable for use as the initial
+    /// value for an empty hash table.
+    ///
+    /// This is guaranteed to be aligned to the group size.
+    #[inline]
+    #[allow(clippy::items_after_statements)]
+    pub(crate) const fn static_empty() -> &'static [u8; Group::WIDTH] {
+        #[repr(C)]
+        struct AlignedBytes {
+            _align: [Group; 0],
+            bytes: [u8; Group::WIDTH],
+        }
+        const ALIGNED_BYTES: AlignedBytes = AlignedBytes {
+            _align: [],
+            bytes: [EMPTY; Group::WIDTH],
+        };
+        &ALIGNED_BYTES.bytes
+    }
+
+    /// Loads a group of bytes starting at the given address.
+    #[inline]
+    #[allow(clippy::cast_ptr_alignment)] // unaligned load
+    pub(crate) unsafe fn load(ptr: *const u8) -> Self {
+        Group(x86::_mm_loadu_si128(ptr.cast()))
+    }
+
+    /// Loads a group of bytes starting at the given address, which must be
+    /// aligned to `mem::align_of::<Group>()`.
+    #[inline]
+    #[allow(clippy::cast_ptr_alignment)]
+    pub(crate) unsafe fn load_aligned(ptr: *const u8) -> Self {
+        // FIXME: use align_offset once it stabilizes
+        debug_assert_eq!(ptr as usize & (mem::align_of::<Self>() - 1), 0);
+        Group(x86::_mm_load_si128(ptr.cast()))
+    }
+
+    /// Stores the group of bytes to the given address, which must be
+    /// aligned to `mem::align_of::<Group>()`.
+    #[inline]
+    #[allow(clippy::cast_ptr_alignment)]
+    pub(crate) unsafe fn store_aligned(self, ptr: *mut u8) {
+        // FIXME: use align_offset once it stabilizes
+        debug_assert_eq!(ptr as usize & (mem::align_of::<Self>() - 1), 0);
+        x86::_mm_store_si128(ptr.cast(), self.0);
+    }
+
+    /// Returns a `BitMask` indicating all bytes in the group which have
+    /// the given value.
+    #[inline]
+    pub(crate) fn match_byte(self, byte: u8) -> BitMask {
+        #[allow(
+            clippy::cast_possible_wrap, // byte: u8 as i8
+            // byte: i32 as u16
+            //   note: _mm_movemask_epi8 returns a 16-bit mask in a i32, the
+            //   upper 16-bits of the i32 are zeroed:
+            clippy::cast_sign_loss,
+            clippy::cast_possible_truncation
+        )]
+        unsafe {
+            let cmp = x86::_mm_cmpeq_epi8(self.0, x86::_mm_set1_epi8(byte as i8));
+            BitMask(x86::_mm_movemask_epi8(cmp) as u16)
+        }
+    }
+
+    /// Returns a `BitMask` indicating all bytes in the group which are
+    /// `EMPTY`.
+    #[inline]
+    pub(crate) fn match_empty(self) -> BitMask {
+        self.match_byte(EMPTY)
+    }
+
+    /// Returns a `BitMask` indicating all bytes in the group which are
+    /// `EMPTY` or `DELETED`.
+    #[inline]
+    pub(crate) fn match_empty_or_deleted(self) -> BitMask {
+        #[allow(
+            // byte: i32 as u16
+            //   note: _mm_movemask_epi8 returns a 16-bit mask in a i32, the
+            //   upper 16-bits of the i32 are zeroed:
+            clippy::cast_sign_loss,
+            clippy::cast_possible_truncation
+        )]
+        unsafe {
+            // A byte is EMPTY or DELETED iff the high bit is set
+            BitMask(x86::_mm_movemask_epi8(self.0) as u16)
+        }
+    }
+
+    /// Returns a `BitMask` indicating all bytes in the group which are full.
+    #[inline]
+    pub(crate) fn match_full(&self) -> BitMask {
+        self.match_empty_or_deleted().invert()
+    }
+
+    /// Performs the following transformation on all bytes in the group:
+    /// - `EMPTY => EMPTY`
+    /// - `DELETED => EMPTY`
+    /// - `FULL => DELETED`
+    #[inline]
+    pub(crate) fn convert_special_to_empty_and_full_to_deleted(self) -> Self {
+        // Map high_bit = 1 (EMPTY or DELETED) to 1111_1111
+        // and high_bit = 0 (FULL) to 1000_0000
+        //
+        // Here's this logic expanded to concrete values:
+        //   let special = 0 > byte = 1111_1111 (true) or 0000_0000 (false)
+        //   1111_1111 | 1000_0000 = 1111_1111
+        //   0000_0000 | 1000_0000 = 1000_0000
+        #[allow(
+            clippy::cast_possible_wrap, // byte: 0x80_u8 as i8
+        )]
+        unsafe {
+            let zero = x86::_mm_setzero_si128();
+            let special = x86::_mm_cmpgt_epi8(zero, self.0);
+            Group(x86::_mm_or_si128(
+                special,
+                x86::_mm_set1_epi8(0x80_u8 as i8),
+            ))
+        }
+    }
+}