[−][src]Crate id_arena
A simple, id-based arena.
Id-based
Allocate objects and get an identifier for that object back, not a reference to the allocated object. Given an id, you can get a shared or exclusive reference to the allocated object from the arena. This id-based approach is useful for constructing mutable graph data structures.
If you want allocation to return a reference, consider the typed-arena
crate instead.
No Deletion
This arena does not support deletion, which makes its implementation simple
and allocation fast. If you want deletion, you need a way to solve the ABA
problem. Consider using the generational-arena
crate instead.
Homogeneous
This crate's arenas can only contain objects of a single type T
. If you
need an arena of objects with heterogeneous types, consider another crate.
#![no_std]
Support
Requires the alloc
nightly feature. Disable the on-by-default "std"
feature:
[dependencies.id-arena]
version = "2"
default-features = false
rayon
Support
If the rayon
feature of this crate is activated:
[dependencies]
id-arena = { version = "2", features = ["rayon"] }
then you can use rayon
's support for
parallel iteration. The Arena
type will have a par_iter
family of
methods where appropriate.
Example
use id_arena::{Arena, Id}; type AstNodeId = Id<AstNode>; #[derive(Debug, Eq, PartialEq)] pub enum AstNode { Const(i64), Var(String), Add { lhs: AstNodeId, rhs: AstNodeId, }, Sub { lhs: AstNodeId, rhs: AstNodeId, }, Mul { lhs: AstNodeId, rhs: AstNodeId, }, Div { lhs: AstNodeId, rhs: AstNodeId, }, } let mut ast_nodes = Arena::<AstNode>::new(); // Create the AST for `a * (b + 3)`. let three = ast_nodes.alloc(AstNode::Const(3)); let b = ast_nodes.alloc(AstNode::Var("b".into())); let b_plus_three = ast_nodes.alloc(AstNode::Add { lhs: b, rhs: three, }); let a = ast_nodes.alloc(AstNode::Var("a".into())); let a_times_b_plus_three = ast_nodes.alloc(AstNode::Mul { lhs: a, rhs: b_plus_three, }); // Can use indexing to access allocated nodes. assert_eq!(ast_nodes[three], AstNode::Const(3));
Structs
Arena | An arena of objects of type |
DefaultArenaBehavior | The default |
Id | An identifier for an object allocated within an arena. |
IntoIter | An iterator over |
IntoParIter | A parallel iterator over items in an arena. |
Iter | An iterator over |
IterMut | An iterator over |
ParIter | A parallel iterator over shared references in an arena. |
ParIterMut | A parallel iterator over mutable references in an arena. |
Traits
ArenaBehavior | A trait representing the implementation behavior of an arena and how identifiers are represented. |