commit	cb4f55b8645774fdefb3918377bff6867eb9d9b0	[log] [tgz]
author	Android Build Coastguard Worker <[email protected]>	Wed Sep 04 15:33:46 2024 +0000
committer	Android Build Coastguard Worker <[email protected]>	Wed Sep 04 15:33:46 2024 +0000
tree	c93a8d21f04dac839395ed8a692c94d67fc85080
parent	461750be822de3976de2daede75fecd77ad8e513 [diff]
parent	ac8fdc26842f8ae4be908afb8dd10fdd83726099 [diff]

tree: c93a8d21f04dac839395ed8a692c94d67fc85080

README.md

pin-project

A crate for safe and ergonomic pin-projection.

Usage

Add this to your Cargo.toml:

[dependencies]
pin-project = "1"

Compiler support: requires rustc 1.56+

Examples

#[pin_project] attribute creates projection types covering all the fields of struct or enum.

use std::pin::Pin;

use pin_project::pin_project;

#[pin_project]
struct Struct<T, U> {
    #[pin]
    pinned: T,
    unpinned: U,
}

impl<T, U> Struct<T, U> {
    fn method(self: Pin<&mut Self>) {
        let this = self.project();
        let _: Pin<&mut T> = this.pinned; // Pinned reference to the field
        let _: &mut U = this.unpinned; // Normal reference to the field
    }
}

code like this will be generated

To use #[pin_project] on enums, you need to name the projection type returned from the method.

use std::pin::Pin;

use pin_project::pin_project;

#[pin_project(project = EnumProj)]
enum Enum<T, U> {
    Pinned(#[pin] T),
    Unpinned(U),
}

impl<T, U> Enum<T, U> {
    fn method(self: Pin<&mut Self>) {
        match self.project() {
            EnumProj::Pinned(x) => {
                let _: Pin<&mut T> = x;
            }
            EnumProj::Unpinned(y) => {
                let _: &mut U = y;
            }
        }
    }
}

code like this will be generated

See #[pin_project] attribute for more details, and see examples directory for more examples and generated code.

Related Projects

pin-project-lite: A lightweight version of pin-project written with declarative macros.

License

Licensed under either of Apache License, Version 2.0 or MIT license at your option.

Unless you explicitly state otherwise, any contribution intentionally submitted for inclusion in the work by you, as defined in the Apache-2.0 license, shall be dual licensed as above, without any additional terms or conditions.