此Rust模块为实现了Copy的类型提供内存分配区域。

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示例

基本用法如下

extern crate copy_arena;

use copy_arena::Arena;

let mut arena = Arena::new();
let mut allocator = arena.allocator();

let a: &mut i32 = allocator.alloc(5);
let b: &mut f64 = allocator.alloc_default();
let c: &mut [u8] = allocator.alloc_slice(b"some text");
let b: &mut [usize] = allocator.alloc_slice_fn(10, |idx| idx + 1);
let e: &mut [u32] = allocator.alloc_slice_default(10);

这可以用于构建树结构，每个节点无需堆分配

use copy_arena::{Arena, Allocator};

#[derive(Copy, Clone)]
struct Tree<'a> {
    left: Option<&'a Tree<'a>>,
    right: Option<&'a Tree<'a>>,
    content: u32
}

fn build_little_tree<'a>(allocator: &mut Allocator<'a>) -> &'a Tree<'a> {
    let left = allocator.alloc(Tree { left: None, right: None, content: 8 });
    let right = allocator.alloc(Tree { left: None, right: None, content: 16 });
    let parent = allocator.alloc(Tree { left: Some(left), right: Some(right), content: 13 });

    parent
}

#[test]
fn make_tree() {
    let mut arena = Arena::new();
    let mut allocator = arena.allocator();

    let root = build_little_tree(&mut allocator);
    assert_eq!(root.content, 13);
    assert_eq!(root.left.unwrap().content, 8);
    assert_eq!(root.right.unwrap().content, 16);
}

与std::arena::Arena相比

此区域与Rust标准库中的（不稳定）区域在几个方面有所不同

• 此区域仅支持可Copy对象 -- 不会执行析构函数。
• 此区域不使用动态借用检查，在获取要分配的底层数据之前节省了两个RefCells和一个Rc，但导致API略微不便。