Struct mnemos_bitslab::index::IndexAlloc16

pub struct IndexAlloc16 {
    bitmap: AtomicU16,
    max_mask: u16,
}

An allocator for up to $cap unique indices.

Fields

bitmap: AtomicU16

max_mask: u16

Implementations

impl IndexAlloc16

pub const fn new() -> Self

Returns a new allocator for up to $cap unique indices.

pub const fn with_capacity(capacity: u8) -> Self

Returns a new allocator for up to capacity unique indices. If capacity indices are allocated, subsequent calls to allocate() will return None until an index is deallocated by a call to free() on this allocator.

A IndexAlloc16 can only ever allocate up to Self::MAX_CAPACITY indices. Therefore, if the provided capacity exceeds Self::MAX_CAPACITY, it will be clamped to the maximum capacity.

An allocator’s actual capacity can be returned

pub fn allocate(&self) -> Option<u8>

Allocate an index from the pool.

If this method returns Some, the returned u8 index will not be returned again until after it has been freed.

pub const MAX_CAPACITY: u8 = 16u8

The maximum number of indices that can be allocated by an allocator of this type.

pub fn free(&self, index: u8)

Release an index back to the pool.

The freed index may now be returned by a subsequent call to allocate.

pub fn all_allocated(&self) -> bool

Returns true if all indices in the allocator have been allocated.

This is the inverse of any_free.

Examples

 use mnemos_bitslab::index::IndexAlloc16;

 let alloc = IndexAlloc16::new();
assert!(!alloc.all_allocated());

// allocate all but one index
 for _ in 1..16 {
    alloc.allocate().expect("should have free indices");
    assert!(!alloc.all_allocated());
}

// allocate the last index.
let last = alloc.allocate().expect("should have one more index remaining");
assert!(alloc.all_allocated());

// freeing the index should make it available again
alloc.free(last);
assert!(!alloc.all_allocated());

pub fn all_free(&self) -> bool

Returns true if none of this allocator’s indices have been allocated.

This is the inverse of any_allocated.

Examples

 use mnemos_bitslab::index::IndexAlloc16;

 let alloc = IndexAlloc16::new();
assert!(alloc.all_free());

let idx = alloc.allocate().expect("a fresh allocator should have indices!");
assert!(!alloc.all_free());

// free the last index. now, `all_free` will return `true` again.
alloc.free(idx);
assert!(alloc.all_free());

pub fn any_allocated(&self) -> bool

Returns true if any index in the allocator has been allocated.

This is the inverse of all_free.

Examples

 use mnemos_bitslab::index::IndexAlloc16;

 let alloc = IndexAlloc16::new();
assert!(!alloc.any_allocated());

// allocate all indices
 for _ in 0..16 {
    alloc.allocate().expect("should have free indices");
    assert!(alloc.any_allocated());
}

// free all but one index.
 for i in 1..IndexAlloc16::MAX_CAPACITY {
    alloc.free(i);
    assert!(alloc.any_allocated());
}

// free the last index. now, `any_allocated` will return `false`.
alloc.free(0);
assert!(!alloc.any_allocated());

pub fn any_free(&self) -> bool

Returns true if any index in the allocator is available.

This is the inverse of all_allocated.

Examples

 use mnemos_bitslab::index::IndexAlloc16;

 let alloc = IndexAlloc16::new();
assert!(alloc.any_free());

// allocate all but one index
 for _ in 1..16 {
    alloc.allocate().expect("should have free indices");
    assert!(alloc.any_free());
}

// allocate the last index.
let last = alloc.allocate().expect("should have one more index remaining");
assert!(!alloc.any_free());

// freeing the index should make it available again
alloc.free(last);
assert!(alloc.any_free());

pub fn free_count(&self) -> u8

Returns the current number of free indices in the allocator.

This will always be [self.capacity()] or less.

 use mnemos_bitslab::index::IndexAlloc16;

 let alloc = IndexAlloc16::new();
assert_eq!(alloc.free_count(), alloc.capacity());

let idx1 = alloc.allocate().expect("all indices should be free");
assert_eq!(alloc.free_count(), alloc.capacity() - 1);

let idx2 = alloc.allocate().expect("most indices should be free");
assert_eq!(alloc.free_count(), alloc.capacity() - 2);

alloc.free(idx1);
assert_eq!(alloc.free_count(), alloc.capacity() - 1);

pub fn allocated_count(&self) -> u8

Returns the current number of allocated indices in the allocator.

This will always be [self.capacity()] or less.

Examples

 use mnemos_bitslab::index::IndexAlloc16;

 let alloc = IndexAlloc16::new();
assert_eq!(alloc.allocated_count(), 0);

let idx1 = alloc.allocate().expect("all indices should be free");
assert_eq!(alloc.allocated_count(), 1);

let idx2 = alloc.allocate().expect("most indices should be free");
assert_eq!(alloc.allocated_count(), 2);

alloc.free(idx1);
assert_eq!(alloc.allocated_count(), 1);

pub const fn capacity(&self) -> u8

Returns the total capacity of this allocator, including any allocated indices.

pub fn iter_allocated(&self) -> AllocatedIndices

Returns an iterator over the indices that have been allocated at the current point in time.

const fn capacity_subtractor(&self) -> u8

fn find_zero(u: u16) -> Option<u8>

Trait Implementations

impl Debug for IndexAlloc16

fn fmt(&self, f: &mut Formatter<'_>) -> Result

Formats the value using the given formatter.

impl Default for IndexAlloc16

fn default() -> Self

Returns the “default value” for a type.