93 lines
2.3 KiB
Rust
93 lines
2.3 KiB
Rust
#[cfg(test)]
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mod tests;
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use {
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crate::ptr_ext::MutPtrExt,
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std::{
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array,
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cell::UnsafeCell,
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fmt::{Debug, Formatter},
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marker::PhantomData,
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},
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};
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type Seg = usize;
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const SEG_SIZE: usize = size_of::<Seg>() * 8;
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pub struct FreeList<T, const N: usize> {
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levels: UnsafeCell<[Vec<Seg>; N]>,
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_phantom: PhantomData<T>,
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}
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impl<T, const N: usize> Default for FreeList<T, N> {
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fn default() -> Self {
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Self {
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levels: UnsafeCell::new(array::from_fn(|_| Vec::new())),
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_phantom: Default::default(),
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}
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}
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}
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impl<T, const N: usize> Debug for FreeList<T, N> {
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fn fmt(&self, f: &mut Formatter<'_>) -> std::fmt::Result {
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f.debug_struct("FreeList")
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.field("levels", self.get())
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.finish()
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}
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}
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impl<T, const N: usize> FreeList<T, N> {
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fn get(&self) -> &mut [Vec<Seg>; N] {
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unsafe { self.levels.get().deref_mut() }
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}
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pub fn release(&self, n: T)
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where
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T: Into<u32>,
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{
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let mut ext = n.into() as usize;
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let mut int;
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let levels = self.get();
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assert!(ext / SEG_SIZE < levels[0].len());
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for level in self.get() {
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int = ext % SEG_SIZE;
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ext /= SEG_SIZE;
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unsafe {
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*level.get_unchecked_mut(ext) |= 1 << int;
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}
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}
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}
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pub fn acquire(&self) -> T
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where
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u32: Into<T>,
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{
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let mut ext = 'last: {
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let level = &mut self.get()[N - 1];
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for (idx, &seg) in level.iter().enumerate() {
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if seg != 0 {
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break 'last idx;
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}
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}
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level.len()
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};
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for level in self.get().iter_mut().rev() {
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if ext == level.len() {
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level.push(!0);
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}
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let seg = unsafe { level.get_unchecked(ext) };
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ext = SEG_SIZE * ext + seg.trailing_zeros() as usize;
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}
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let id = ext as u32;
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for level in self.get().iter_mut() {
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let int = ext % SEG_SIZE;
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ext /= SEG_SIZE;
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let seg = unsafe { level.get_unchecked_mut(ext) };
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*seg &= !(1 << int);
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if *seg != 0 {
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break;
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}
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}
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id.into()
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}
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}
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