Google Git
Sign in
android / toolchain / rustc / 5139364148b53d79de1b5e778004d41a6a33a4a2 / . / vendor / hashbrown-0.14.0 / src / raw / mod.rs
blob: 1a6dced4b097046e390ab049dae0c487d9e166d8 [file] [log] [blame]
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::ManuallyDrop;
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),
}
}
}
/// 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> {
const IS_ZERO_SIZED_TYPE: bool = mem::size_of::<T>() == 0;
/// 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 Self::IS_ZERO_SIZED_TYPE {
// 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 Self::IS_ZERO_SIZED_TYPE {
// 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 Self::IS_ZERO_SIZED_TYPE {
// 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 Self::IS_ZERO_SIZED_TYPE {
// 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 + Clone = Global> {
table: RawTableInner<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<A> {
// 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,
alloc: A,
}
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_in(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 + Clone> RawTable<T, A> {
const TABLE_LAYOUT: TableLayout = TableLayout::new::<T>();
const DATA_NEEDS_DROP: bool = mem::needs_drop::<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_in(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,
)?,
marker: PhantomData,
})
}
/// Attempts to allocate a new hash table with at least enough capacity
/// for inserting the given number of elements without reallocating.
fn fallible_with_capacity(
alloc: A,
capacity: usize,
fallibility: Fallibility,
) -> Result<Self, TryReserveError> {
Ok(Self {
table: RawTableInner::fallible_with_capacity(
alloc,
Self::TABLE_LAYOUT,
capacity,
fallibility,
)?,
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> {
Self::fallible_with_capacity(alloc, capacity, Fallibility::Fallible)
}
/// 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 {
// Avoid `Result::unwrap_or_else` because it bloats LLVM IR.
match Self::fallible_with_capacity(alloc, capacity, Fallibility::Infallible) {
Ok(capacity) => capacity,
Err(_) => unsafe { hint::unreachable_unchecked() },
}
}
/// Returns a reference to the underlying allocator.
#[inline]
pub fn allocator(&self) -> &A {
&self.table.alloc
}
/// Deallocates the table without dropping any entries.
#[cfg_attr(feature = "inline-more", inline)]
unsafe fn free_buckets(&mut self) {
self.table.free_buckets(Self::TABLE_LAYOUT);
}
/// 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) {
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 {
self_.drop_elements();
}
}
unsafe fn drop_elements(&mut self) {
if Self::DATA_NEEDS_DROP && !self.is_empty() {
for item in self.iter() {
item.drop();
}
}
}
/// 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 {
*self = Self::new_in(self.table.alloc.clone());
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 {
*self = Self::with_capacity_in(min_size, self.table.alloc.clone());
} else {
// Avoid `Result::unwrap_or_else` because it bloats LLVM IR.
if self
.resize(min_size, hasher, Fallibility::Infallible)
.is_err()
{
unsafe { 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.
if self
.reserve_rehash(additional, hasher, Fallibility::Infallible)
.is_err()
{
unsafe { 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 {
self.reserve_rehash(additional, hasher, Fallibility::Fallible)
} else {
Ok(())
}
}
/// Out-of-line slow path for `reserve` and `try_reserve`.
#[cold]
#[inline(never)]
fn reserve_rehash(
&mut self,
additional: usize,
hasher: impl Fn(&T) -> u64,
fallibility: Fallibility,
) -> Result<(), TryReserveError> {
unsafe {
self.table.reserve_rehash_inner(
additional,
&|table, index| hasher(table.bucket::<T>(index).as_ref()),
fallibility,
Self::TABLE_LAYOUT,
if Self::DATA_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.
fn resize(
&mut self,
capacity: usize,
hasher: impl Fn(&T) -> u64,
fallibility: Fallibility,
) -> Result<(), TryReserveError> {
unsafe {
self.table.resize_inner(
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 {
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.
let old_ctrl = *self.table.ctrl(slot.index);
if unlikely(self.table.growth_left == 0 && special_is_empty(old_ctrl)) {
self.reserve(1, hasher);
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);
match self
.table
.find_or_find_insert_slot_inner(hash, &mut |index| unsafe {
eq(self.bucket(index).as_ref())
}) {
Ok(index) => Ok(unsafe { 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>> {
let result = self.table.find_inner(hash, &mut |index| unsafe {
eq(self.bucket(index).as_ref())
});
// Avoid `Option::map` because it bloats LLVM IR.
match result {
Some(index) => Some(unsafe { 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> {
let data = Bucket::from_base_index(self.data_end(), 0);
RawIter {
iter: RawIterRange::new(self.table.ctrl.as_ptr(), data, self.table.buckets()),
items: self.table.items,
}
}
/// 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: ManuallyDrop::new(mem::replace(self, Self::new_in(self.table.alloc.clone()))),
orig_table: NonNull::from(self),
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 alloc = self.table.alloc.clone();
let allocation = self.into_allocation();
RawIntoIter {
iter,
allocation,
marker: PhantomData,
alloc,
}
}
/// 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)> {
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,
))
};
mem::forget(self);
alloc
}
}
unsafe impl<T, A: Allocator + Clone> Send for RawTable<T, A>
where
T: Send,
A: Send,
{
}
unsafe impl<T, A: Allocator + Clone> Sync for RawTable<T, A>
where
T: Sync,
A: Sync,
{
}
impl<A> RawTableInner<A> {
/// 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_in(alloc: A) -> 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,
alloc,
}
}
}
impl<A: Allocator + Clone> RawTableInner<A> {
/// 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(
alloc: A,
table_layout: TableLayout,
buckets: usize,
fallibility: Fallibility,
) -> Result<Self, TryReserveError> {
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),
alloc,
})
}
/// 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(
alloc: A,
table_layout: TableLayout,
capacity: usize,
fallibility: Fallibility,
) -> Result<Self, TryReserveError> {
if capacity == 0 {
Ok(Self::new_in(alloc))
} 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)
}
}
}
/// Fixes up an insertion slot due to false positives for groups smaller than the group width.
/// This must only be used on insertion slots found by `find_insert_slot_in_group`.
#[inline]
unsafe fn fix_insert_slot(&self, mut index: usize) -> InsertSlot {
// 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, but once masked 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).
if unlikely(self.is_bucket_full(index)) {
debug_assert!(self.bucket_mask < Group::WIDTH);
// SAFETY:
//
// * We are in range and `ptr = self.ctrl(0)` are valid for reads
// and properly aligned, because the table is already allocated
// (see `TableLayout::calculate_layout_for` and `ptr::read`);
//
// * 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, 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.
#[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()) {
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.
///
/// This uses dynamic dispatch to reduce the amount of code generated, but that is
/// eliminated by LLVM optimizations.
#[inline]
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 {
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 {
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.
///
/// There must be at least 1 empty bucket in the table.
#[inline]
unsafe fn prepare_insert_slot(&self, hash: u64) -> (usize, u8) {
let index = self.find_insert_slot(hash).index;
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.
///
/// # Note
///
/// Calling this function is always safe, but attempting 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 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]
fn find_insert_slot(&self, hash: u64) -> InsertSlot {
let mut probe_seq = self.probe_seq(hash);
loop {
// SAFETY:
// * `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 comment for masking below).
//
// * 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).
unsafe {
let group = Group::load(self.ctrl(probe_seq.pos));
let index = self.find_insert_slot_in_group(&group, &probe_seq);
if likely(index.is_some()) {
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).
#[inline(always)]
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:
// * `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.
///
/// 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);
}
}
#[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 {
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(&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(&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(&self, index: usize, ctrl: u8) {
// Replicate the first Group::WIDTH control bytes at the end of
// the array without using a branch:
// - 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
}
#[allow(clippy::mut_mut)]
#[inline]
unsafe fn prepare_resize(
&self,
table_layout: TableLayout,
capacity: usize,
fallibility: Fallibility,
) -> Result<crate::scopeguard::ScopeGuard<Self, impl FnMut(&mut Self)>, TryReserveError> {
debug_assert!(self.items <= capacity);
// Allocate and initialize the new table.
let mut new_table = RawTableInner::fallible_with_capacity(
self.alloc.clone(),
table_layout,
capacity,
fallibility,
)?;
new_table.growth_left -= self.items;
new_table.items = self.items;
// 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() {
self_.free_buckets(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.
#[allow(clippy::inline_always)]
#[inline(always)]
unsafe fn reserve_rehash_inner(
&mut self,
additional: usize,
hasher: &dyn Fn(&mut Self, usize) -> u64,
fallibility: Fallibility,
layout: TableLayout,
drop: Option<fn(*mut u8)>,
) -> Result<(), TryReserveError> {
// 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.
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.
self.resize_inner(
usize::max(new_items, full_capacity + 1),
hasher,
fallibility,
layout,
)
}
}
/// 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.
#[allow(clippy::inline_always)]
#[inline(always)]
unsafe fn resize_inner(
&mut self,
capacity: usize,
hasher: &dyn Fn(&mut Self, usize) -> u64,
fallibility: Fallibility,
layout: TableLayout,
) -> Result<(), TryReserveError> {
let mut new_table = self.prepare_resize(layout, capacity, fallibility)?;
// Copy all elements to the new table.
for i in 0..self.buckets() {
if !self.is_bucket_full(i) {
continue;
}
// This may panic.
let hash = hasher(self, i);
// 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, _) = new_table.prepare_insert_slot(hash);
ptr::copy_nonoverlapping(
self.bucket_ptr(i, layout.size),
new_table.bucket_ptr(index, layout.size),
layout.size,
);
}
// 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).
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.
#[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
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);
}
#[inline]
unsafe fn free_buckets(&mut self, table_layout: TableLayout) {
let (ptr, layout) = self.allocation_info(table_layout);
self.alloc.deallocate(ptr, layout);
}
#[inline]
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() },
};
(
unsafe { NonNull::new_unchecked(self.ctrl.as_ptr().sub(ctrl_offset)) },
layout,
)
}
#[cfg(feature = "raw")]
fn allocation_info_or_zero(&self, table_layout: TableLayout) -> (NonNull<u8>, Layout) {
if self.is_empty_singleton() {
(NonNull::dangling(), Layout::new::<()>())
} else {
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.table.alloc.clone())
} else {
unsafe {
// Avoid `Result::ok_or_else` because it bloats LLVM IR.
let new_table = match Self::new_uninitialized(
self.table.alloc.clone(),
self.table.buckets(),
Fallibility::Infallible,
) {
Ok(table) => table,
Err(_) => hint::unreachable_unchecked(),
};
// If cloning fails then we need to free the allocation for the
// new table. However we don't run its drop since its control
// bytes are not initialized yet.
let mut guard = guard(ManuallyDrop::new(new_table), |new_table| {
new_table.free_buckets();
});
guard.clone_from_spec(self);
// Disarm the scope guard and return the newly created table.
ManuallyDrop::into_inner(ScopeGuard::into_inner(guard))
}
}
}
fn clone_from(&mut self, source: &Self) {
if source.table.is_empty_singleton() {
*self = Self::new_in(self.table.alloc.clone());
} 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.
self_.drop_elements();
// If necessary, resize our table to match the source.
if self_.buckets() != source.buckets() {
// Skip our drop by using ptr::write.
if !self_.table.is_empty_singleton() {
self_.free_buckets();
}
(&mut **self_ as *mut Self).write(
// Avoid `Result::unwrap_or_else` because it bloats LLVM IR.
match Self::new_uninitialized(
self_.table.alloc.clone(),
source.buckets(),
Fallibility::Infallible,
) {
Ok(table) => table,
Err(_) => hint::unreachable_unchecked(),
},
);
}
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 Self::DATA_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 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 + Clone + 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 + Clone> Drop for RawTable<T, A> {
#[cfg_attr(feature = "inline-more", inline)]
fn drop(&mut self) {
if !self.table.is_empty_singleton() {
unsafe {
self.drop_elements();
self.free_buckets();
}
}
}
}
#[cfg(not(feature = "nightly"))]
impl<T, A: Allocator + Clone> Drop for RawTable<T, A> {
#[cfg_attr(feature = "inline-more", inline)]
fn drop(&mut self) {
if !self.table.is_empty_singleton() {
unsafe {
self.drop_elements();
self.free_buckets();
}
}
}
}
impl<T, A: Allocator + Clone> 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.
///
/// The control byte address must be aligned to the group size.
#[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);
let end = ctrl.add(len);
// Load the first group and advance ctrl to point to the next group
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> {
const DATA_NEEDS_DROP: bool = mem::needs_drop::<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 Self::DATA_NEEDS_DROP && self.len() != 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 consumes a table and returns elements.
pub struct RawIntoIter<T, A: Allocator + Clone = Global> {
iter: RawIter<T>,
allocation: Option<(NonNull<u8>, Layout)>,
marker: PhantomData<T>,
alloc: A,
}
impl<T, A: Allocator + Clone> RawIntoIter<T, A> {
#[cfg_attr(feature = "inline-more", inline)]
pub fn iter(&self) -> RawIter<T> {
self.iter.clone()
}
}
unsafe impl<T, A: Allocator + Clone> Send for RawIntoIter<T, A>
where
T: Send,
A: Send,
{
}
unsafe impl<T, A: Allocator + Clone> Sync for RawIntoIter<T, A>
where
T: Sync,
A: Sync,
{
}
#[cfg(feature = "nightly")]
unsafe impl<#[may_dangle] T, A: Allocator + Clone> 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)) = self.allocation {
self.alloc.deallocate(ptr, layout);
}
}
}
}
#[cfg(not(feature = "nightly"))]
impl<T, A: Allocator + Clone> 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)) = self.allocation {
self.alloc.deallocate(ptr, layout);
}
}
}
}
impl<T, A: Allocator + Clone> 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 + Clone> ExactSizeIterator for RawIntoIter<T, A> {}
impl<T, A: Allocator + Clone> FusedIterator for RawIntoIter<T, A> {}
/// Iterator which consumes elements without freeing the table storage.
pub struct RawDrain<'a, T, A: Allocator + Clone = 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: ManuallyDrop<RawTable<T, A>>,
orig_table: NonNull<RawTable<T, A>>,
// 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 + Clone> RawDrain<'_, T, A> {
#[cfg_attr(feature = "inline-more", inline)]
pub fn iter(&self) -> RawIter<T> {
self.iter.clone()
}
}
unsafe impl<T, A: Allocator + Copy> Send for RawDrain<'_, T, A>
where
T: Send,
A: Send,
{
}
unsafe impl<T, A: Allocator + Copy> Sync for RawDrain<'_, T, A>
where
T: Sync,
A: Sync,
{
}
impl<T, A: Allocator + Clone> 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 + Clone> 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 + Clone> ExactSizeIterator for RawDrain<'_, T, A> {}
impl<T, A: Allocator + Clone> 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 + Clone>(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<A: Allocator + Clone>(table: &RawTableInner<A>, 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());
}
}
}