[−][src]Crate heapless
static
friendly data structures that don't require dynamic memory allocation
HEADS UP this is a pre-release. There may be more breaking changes before the final release of version v0.5.0.
The core principle behind heapless
is that its data structures are backed by a static memory
allocation. For example, you can think of heapless::Vec
as an alternative version of
std::Vec
with fixed capacity and that can't be re-allocated on the fly (e.g. via push
).
All heapless
data structures store their memory allocation inline and specify their capacity
via their type parameter N
. This means that you can instantiate a heapless
data structure on
the stack, in a static
variable, or even in the heap.
use heapless::Vec; // fixed capacity `std::Vec` use heapless::consts::U8; // type level integer used to specify capacity // on the stack let mut xs: Vec<u8, U8> = Vec::new(); // can hold up to 8 elements xs.push(42).unwrap(); assert_eq!(xs.pop(), Some(42)); // in a `static` variable // (because `const-fn` has not been fully stabilized you need to use the helper structs in // the `i` module, which must be wrapped in a tuple struct) static mut XS: Vec<u8, U8> = Vec(heapless::i::Vec::new()); let xs = unsafe { &mut XS }; xs.push(42); assert_eq!(xs.pop(), Some(42)); // in the heap (though kind of pointless because no reallocation) let mut ys: Box<Vec<u8, U8>> = Box::new(Vec::new()); ys.push(42).unwrap(); assert_eq!(ys.pop(), Some(42));
Because they have fixed capacity heapless
data structures don't implicitly reallocate. This
means that operations like heapless::Vec.push
are truly constant time rather than amortized
constant time with potentially unbounded (depends on the allocator) worst case execution time
(which is bad / unacceptable for hard real time applications).
heapless
data structures don't use a memory allocator which means no risk of an uncatchable
Out Of Memory (OOM) condition while performing operations on them. It's certainly possible to
run out of capacity while growing heapless
data structures, but the API lets you handle this
possibility by returning a Result
on operations that may exhaust the capacity of the data
structure.
List of currently implemented data structures:
BinaryHeap
-- priority queueIndexMap
-- hash tableIndexSet
-- hash setLinearMap
spsc::Queue
-- single producer single consumer lock-free queueString
Vec
Minimum Supported Rust Version (MSRV)
This crate is guaranteed to compile on stable Rust 1.36 and up with its default set of features. It might compile on older versions but that may change in any new patch release.
Re-exports
pub use binary_heap::BinaryHeap; |
Modules
binary_heap | A priority queue implemented with a binary heap. |
consts | Type aliases for many constants. |
i | Unfortunate implementation detail required to construct |
pool | A heap-less, interrupt-safe, lock-free memory pool (*) |
spsc | Single producer single consumer queue |
Structs
IndexMap | Fixed capacity |
IndexSet | Fixed capacity |
LinearMap | A fixed capacity map / dictionary that performs lookups via linear search |
String | A fixed capacity |
Vec | A fixed capacity |
Traits
ArrayLength | Trait making |
Type Definitions
FnvIndexMap | An |
FnvIndexSet | An |