https://github.com/upsuper/default-boxed

Helper trait to create a boxed instance without going through stack
https://github.com/upsuper/default-boxed

rust

Last synced: 3 months ago
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Helper trait to create a boxed instance without going through stack

• Host: GitHub
• URL: https://github.com/upsuper/default-boxed
• Owner: upsuper
• License: mit
• Created: 2019-08-31T12:33:59.000Z (almost 6 years ago)
• Default Branch: master
• Last Pushed: 2022-03-13T10:47:59.000Z (over 3 years ago)
• Last Synced: 2025-04-08T16:06:07.067Z (3 months ago)
• Topics: rust
• Language: Rust
• Homepage:
• Size: 33.2 KB
• Stars: 36
• Watchers: 2
• Forks: 2
• Open Issues: 3
• Metadata Files:
  • Readme: README.md
  • Funding: .github/FUNDING.yml
  • License: LICENSE

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README

        
# default-boxed

[![CI](https://github.com/upsuper/default-boxed/workflows/CI/badge.svg)](https://github.com/upsuper/default-boxed/actions)

[![Crates.io](https://img.shields.io/crates/v/default-boxed.svg)](https://crates.io/crates/default-boxed)

Helper trait to create instances of large structs with default value on heap directly

without going through stack.

Similar to the unstable `box` syntax,

it semantically doesn't require creating the whole struct on stack then moving to heap,

and thus unlike [`copyless`][copyless] or [`boxext`][boxext],

it doesn't rely on optimization to eliminate building the struct on stack,

which may still face stack overflow on debug build when creating large struct.

[copyless]: https://crates.io/crates/copyless

[boxext]: https://crates.io/crates/boxext

## Example

```rust

use default_boxed::DefaultBoxed;

const BASE: usize = 1024;

#[derive(DefaultBoxed)]

struct Foo {

    a: Bar,

    b: [Bar; 1024 * BASE],

    c: [u32; 1024 * BASE],

}

struct Bar(u16);

impl Default for Bar {

    fn default() -> Bar {

        Bar(29)

    }

}

let foo = Foo::default_boxed();

assert_eq!(foo.a.0, 29);

assert_eq!(foo.b[128 * BASE].0, 29);

assert_eq!(foo.c[256 * BASE], 0);

let foo_arr = Foo::default_boxed_array::<16>();

assert_eq!(foo_arr[15].a.0, 29);

```