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Copy pathtable_empty.rs
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149 lines (129 loc) · 3.72 KB
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// Copyright 2021 Datafuse Labs
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
// http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.
use std::alloc::Allocator;
use databend_common_base::runtime::drop_guard;
use super::table0::Entry;
type Ent<V> = Entry<[u8; 0], V>;
pub struct TableEmpty<V, A: Allocator + Clone> {
pub(crate) has_zero: bool,
pub(crate) slice: Box<[Entry<[u8; 0], V>; 1], A>,
pub(crate) allocator: A,
}
impl<V, A: Allocator + Clone + Default> Default for TableEmpty<V, A> {
fn default() -> Self {
Self::new_in(A::default())
}
}
impl<V, A: Allocator + Clone> TableEmpty<V, A> {
pub fn new_in(allocator: A) -> Self {
Self {
has_zero: false,
allocator: allocator.clone(),
slice: unsafe { Box::<[Ent<V>; 1], A>::new_zeroed_in(allocator).assume_init() },
}
}
pub fn capacity(&self) -> usize {
1
}
pub fn len(&self) -> usize {
usize::from(self.has_zero)
}
pub fn heap_bytes(&self) -> usize {
std::mem::size_of::<Ent<V>>()
}
pub fn get(&self) -> Option<&Ent<V>> {
if self.has_zero {
Some(&self.slice[0])
} else {
None
}
}
pub fn get_mut(&mut self) -> Option<&mut Ent<V>> {
if self.has_zero {
Some(&mut self.slice[0])
} else {
None
}
}
/// # Safety
///
/// The resulted `MaybeUninit` should be initialized immediately.
pub fn insert(&mut self) -> Result<&mut Ent<V>, &mut Ent<V>> {
if !self.has_zero {
self.has_zero = true;
Ok(&mut self.slice[0])
} else {
Err(&mut self.slice[0])
}
}
pub fn iter(&self) -> TableEmptyIter<'_, V> {
TableEmptyIter {
slice: self.slice.as_ref(),
i: usize::from(!self.has_zero),
}
}
pub fn clear(&mut self) {
unsafe {
self.has_zero = false;
let allocator = self.allocator.clone();
self.slice = Box::<[Ent<V>; 1], A>::new_zeroed_in(allocator).assume_init();
}
}
}
impl<V, A: Allocator + Clone> Drop for TableEmpty<V, A> {
fn drop(&mut self) {
drop_guard(move || {
if std::mem::needs_drop::<V>() && self.has_zero {
unsafe {
self.slice[0].val.assume_init_drop();
}
}
})
}
}
pub struct TableEmptyIter<'a, V> {
slice: &'a [Ent<V>; 1],
i: usize,
}
impl<'a, V> Iterator for TableEmptyIter<'a, V> {
type Item = &'a Ent<V>;
fn next(&mut self) -> Option<Self::Item> {
if self.i > 0 {
None
} else {
self.i += 1;
Some(&self.slice[0])
}
}
fn size_hint(&self) -> (usize, Option<usize>) {
let len = if self.i > 0 { 0 } else { 1 };
(len, Some(len))
}
}
pub struct TableEmptyIterMut<'a, V> {
slice: &'a mut [Ent<V>; 1],
i: usize,
}
impl<'a, V> Iterator for TableEmptyIterMut<'a, V> {
type Item = &'a mut Ent<V>;
fn next(&mut self) -> Option<Self::Item> {
if self.i > 0 {
None
} else {
let res = unsafe { &mut *(self.slice.as_ptr().add(self.i) as *mut _) };
self.i += 1;
Some(res)
}
}
}