100 lines
3.0 KiB
Markdown
100 lines
3.0 KiB
Markdown
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# pin-project
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[](https://crates.io/crates/pin-project)
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[](https://docs.rs/pin-project)
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[](#license)
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[](https://www.rust-lang.org)
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[](https://github.com/taiki-e/pin-project/actions)
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A crate for safe and ergonomic [pin-projection].
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## Usage
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Add this to your `Cargo.toml`:
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```toml
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[dependencies]
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pin-project = "1"
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```
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*Compiler support: requires rustc 1.37+*
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## Examples
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[`#[pin_project]`][`pin_project`] attribute creates projection types
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covering all the fields of struct or enum.
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```rust
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use pin_project::pin_project;
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use std::pin::Pin;
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#[pin_project]
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struct Struct<T, U> {
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#[pin]
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pinned: T,
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unpinned: U,
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}
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impl<T, U> Struct<T, U> {
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fn method(self: Pin<&mut Self>) {
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let this = self.project();
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let _: Pin<&mut T> = this.pinned; // Pinned reference to the field
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let _: &mut U = this.unpinned; // Normal reference to the field
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}
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}
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```
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[*code like this will be generated*][struct-default-expanded]
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To use `#[pin_project]` on enums, you need to name the projection type
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returned from the method.
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```rust
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use pin_project::pin_project;
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use std::pin::Pin;
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#[pin_project(project = EnumProj)]
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enum Enum<T, U> {
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Pinned(#[pin] T),
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Unpinned(U),
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}
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impl<T, U> Enum<T, U> {
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fn method(self: Pin<&mut Self>) {
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match self.project() {
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EnumProj::Pinned(x) => {
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let _: Pin<&mut T> = x;
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}
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EnumProj::Unpinned(y) => {
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let _: &mut U = y;
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}
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}
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}
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}
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```
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[*code like this will be generated*][enum-default-expanded]
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See [documentation](https://docs.rs/pin-project) for more details, and
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see [examples] directory for more examples and generated code.
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## Related Projects
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- [pin-project-lite]: A lightweight version of pin-project written with declarative macros.
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[`pin_project`]: https://docs.rs/pin-project/1/pin_project/attr.pin_project.html
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[enum-default-expanded]: examples/enum-default-expanded.rs
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[examples]: examples/README.md
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[pin-project-lite]: https://github.com/taiki-e/pin-project-lite
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[pin-projection]: https://doc.rust-lang.org/std/pin/index.html#projections-and-structural-pinning
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[struct-default-expanded]: examples/struct-default-expanded.rs
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## License
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Licensed under either of [Apache License, Version 2.0](LICENSE-APACHE) or
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[MIT license](LICENSE-MIT) at your option.
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Unless you explicitly state otherwise, any contribution intentionally submitted
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for inclusion in the work by you, as defined in the Apache-2.0 license, shall
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be dual licensed as above, without any additional terms or conditions.
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