pub struct Bucket<T> { /* private fields */ }
Expand description
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.
Implementations§
Source§impl<T> Bucket<T>
impl<T> Bucket<T>
Sourcepub fn as_ptr(&self) -> *mut T
pub fn as_ptr(&self) -> *mut T
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.
§Examples
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));
Sourcepub unsafe fn as_ref<'a>(&self) -> &'a T
pub unsafe fn as_ref<'a>(&self) -> &'a T
Returns a shared immutable reference to the value
.
§Safety
See NonNull::as_ref
for safety concerns.
§Examples
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())
);
Sourcepub unsafe fn as_mut<'a>(&self) -> &'a mut T
pub unsafe fn as_mut<'a>(&self) -> &'a mut T
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.
§Examples
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()
)
);
Sourcepub unsafe fn copy_from_nonoverlapping(&self, other: &Self)
pub unsafe fn copy_from_nonoverlapping(&self, other: &Self)
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.