1// This file is part of ICU4X. For terms of use, please see the file
2// called LICENSE at the top level of the ICU4X source tree
3// (online at: https://github.com/unicode-org/icu4x/blob/main/LICENSE ).
4
5//! This crate provides [`Yoke<Y, C>`][Yoke], which allows one to "yoke" (attach) a zero-copy deserialized
6//! object (say, a [`Cow<'a, str>`](alloc::borrow::Cow)) to the source it was deserialized from, (say, an [`Rc<[u8]>`](alloc::rc::Rc)),
7//! known in this crate as a "cart", producing a type that looks like `Yoke<Cow<'static, str>, Rc<[u8]>>`
8//! and can be moved around with impunity.
9//!
10//! Succinctly, this allows one to "erase" static lifetimes and turn them into dynamic ones, similarly
11//! to how `dyn` allows one to "erase" static types and turn them into dynamic ones.
12//!
13//! Most of the time the yokeable `Y` type will be some kind of zero-copy deserializable
14//! abstraction, potentially with an owned variant (like [`Cow`](alloc::borrow::Cow),
15//! [`ZeroVec`](https://docs.rs/zerovec), or an aggregate containing such types), and the cart `C` will be some smart pointer like
16//! [`Box<T>`](alloc::boxed::Box), [`Rc<T>`](alloc::rc::Rc), or [`Arc<T>`](std::sync::Arc), potentially wrapped in an [`Option<T>`](Option).
17//!
18//! The key behind this crate is [`Yoke::get()`], where calling [`.get()`][Yoke::get] on a type like
19//! `Yoke<Cow<'static, str>, _>` will get you a short-lived `&'a Cow<'a, str>`, restricted to the
20//! lifetime of the borrow used during [`.get()`](Yoke::get). This is entirely safe since the `Cow` borrows from
21//! the cart type `C`, which cannot be interfered with as long as the `Yoke` is borrowed by [`.get()`](Yoke::get).
22//! [`.get()`](Yoke::get) protects access by essentially reifying the erased lifetime to a safe local one
23//! when necessary.
24//!
25//! See the documentation of [`Yoke`] for more details.
26
27// https://github.com/unicode-org/icu4x/blob/main/documents/process/boilerplate.md#library-annotations
28#![cfg_attr(all(not(test), not(doc)), no_std)]
29#![cfg_attr(
30 not(test),
31 deny(
32 clippy::indexing_slicing,
33 clippy::unwrap_used,
34 clippy::expect_used,
35 clippy::panic,
36 clippy::exhaustive_structs,
37 clippy::exhaustive_enums,
38 missing_debug_implementations,
39 )
40)]
41// The lifetimes here are important for safety and explicitly writing
42// them out is good even when redundant
43#![allow(clippy::needless_lifetimes)]
44
45#[cfg(feature = "alloc")]
46extern crate alloc;
47
48pub mod cartable_ptr;
49pub mod either;
50#[cfg(feature = "alloc")]
51pub mod erased;
52mod kinda_sorta_dangling;
53mod macro_impls;
54pub mod trait_hack;
55mod yoke;
56mod yokeable;
57#[cfg(feature = "zerofrom")]
58mod zero_from;
59
60#[cfg(feature = "derive")]
61pub use yoke_derive::Yokeable;
62
63pub use crate::yoke::{CloneableCart, Yoke};
64pub use crate::yokeable::Yokeable;
65
66#[cfg(feature = "zerofrom")]
67use zerofrom::ZeroFrom;
68