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use crate::{BitSet, BitSetMut};
#[derive(Debug)]
pub struct Layered<T, B, const N: usize> {
top: T,
bottom: [B; N],
}
impl<T, B, const N: usize> Default for Layered<T, B, N>
where
T: Default + BitSet,
B: Default + BitSet,
{
fn default() -> Self {
Self::new()
}
}
impl<T, B, const N: usize> Layered<T, B, N>
where
T: BitSet,
B: BitSet,
{
fn new() -> Self
where
T: Default,
B: Default,
{
assert_eq!(T::UPPER_BOUND, N as u32);
assert_eq!(T::UPPER_BOUND as usize, N);
use core::mem::MaybeUninit;
let bottom = unsafe {
let mut array: [MaybeUninit<B>; N] = MaybeUninit::uninit().assume_init();
for item in &mut array {
core::ptr::write(item, MaybeUninit::new(B::default()));
}
(&array as *const _ as *const [B; N]).read()
};
Layered {
top: T::default(),
bottom,
}
}
}
impl<T, B, const N: usize> BitSet for Layered<T, B, N>
where
T: BitSet,
B: BitSet,
{
const UPPER_BOUND: u32 = B::UPPER_BOUND * N as u32;
fn get(&self, index: u32) -> bool {
assert!(index < Self::UPPER_BOUND);
let t = index / B::UPPER_BOUND;
let b = index % B::UPPER_BOUND;
self.bottom[t as usize].get(b)
}
fn find_set(&self, lower_bound: u32) -> Option<u32> {
assert!(lower_bound < Self::UPPER_BOUND);
let t = lower_bound / B::UPPER_BOUND;
let b = lower_bound % B::UPPER_BOUND;
if b == 0 {
let t = self.top.find_set(t)?;
let b = self.bottom[t as usize].find_set(0)?;
Some(t * B::UPPER_BOUND + b)
} else {
if self.top.get(t) {
if let Some(b) = self.bottom[t as usize].find_set(b) {
return Some(t * B::UPPER_BOUND + b);
}
}
let t = self.top.find_set(t + 1)?;
let b = self.bottom[t as usize].find_set(0)?;
Some(t * B::UPPER_BOUND + b)
}
}
}
impl<T, B, const N: usize> BitSetMut for Layered<T, B, N>
where
T: BitSetMut,
B: BitSetMut,
{
fn set(&mut self, index: u32, bit: bool) {
assert!(index < Self::UPPER_BOUND);
let t = index / B::UPPER_BOUND;
let u = index % B::UPPER_BOUND;
if bit {
if !self.top.get(t) {
self.top.set(t, true);
}
self.bottom[t as usize].set(u, true)
} else {
if self.top.get(t) {
self.bottom[t as usize].set(u, false);
if self.bottom[t as usize].is_empty() {
self.top.set(t, false);
}
}
}
}
}