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Add little notes for BitAllocator

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This commit is contained in:
dzy 2018-09-07 20:53:37 +08:00
parent 30a569d889
commit 906019f7c6
2 changed files with 17 additions and 1 deletions
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15
crate/bit-allocator/src/lib.rs
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@ -6,6 +6,18 @@ extern crate bit_field;
use bit_field::BitField;
use core::ops::Range;
/// Allocator of a bitmap, able to allocate / free bits.
///
/// CAP: the bitmap has a total of CAP bits, numbered from 0 to CAP-1 inclusively.
///
/// alloc: allocate a free bit.
/// dealloc: free an allocated bit.
///
/// insert: mark bits in the range as allocated
/// remove: reverse of insert
///
/// any: whether there are free bits remaining
/// test: whether a specific bit is free
pub trait BitAlloc: Default {
const CAP: usize;
fn alloc(&mut self) -> Option<usize>;
@ -23,6 +35,7 @@ pub type BitAlloc1M = BitAllocCascade16<BitAlloc64K>;
pub type BitAlloc16M = BitAllocCascade16<BitAlloc1M>;
pub type BitAlloc256M = BitAllocCascade16<BitAlloc16M>;
/// Implement the bit allocator by segment tree algorithm.
#[derive(Default)]
pub struct BitAllocCascade16<T: BitAlloc> {
bitset: u16,
@ -77,6 +90,8 @@ impl<T: BitAlloc> BitAllocCascade16<T> {
#[derive(Default)]
pub struct BitAlloc16(u16);
/// BitAlloc16 acts as the leaf (except the leaf bits of course) nodes
/// in the segment trees.
impl BitAlloc for BitAlloc16 {
const CAP: usize = 16;

3
crate/process/src/scheduler.rs
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@ -211,4 +211,5 @@ mod stride {
fn expand<T: Default + Clone>(vec: &mut Vec<T>, id: usize) {
let len = vec.len();
vec.resize(len.max(id + 1), T::default());
}
}