| commit | 2ec915de48d05ebef1036c260dba9df8ad2e3796 | [log] [tgz] |
|---|---|---|
| author | Pierre-Clément Tosi <ptosi@google.com> | Thu Feb 08 12:09:25 2024 +0000 |
| committer | Automerger Merge Worker <android-build-automerger-merge-worker@system.gserviceaccount.com> | Thu Feb 08 12:09:25 2024 +0000 |
| tree | 5fbd5ddd8774ca28a9cc56a7d1fb7d518207542c | |
| parent | b3fe3a0de43727c61310d2484bb0326a0085d868 [diff] | |
| parent | 320bea9721ac714b355f7d72ca927136c8d5a888 [diff] |
Bring back upstream support for no_std in Android am: e2e12f853d am: 320bea9721 Original change: https://android-review.googlesource.com/c/platform/external/rust/crates/memoffset/+/2952668 Change-Id: Ic32a5419ab3666bf8f941ce70f80fe1f7fca20a5 Signed-off-by: Automerger Merge Worker <android-build-automerger-merge-worker@system.gserviceaccount.com>
C-Like offset_of functionality for Rust structs.
Introduces the following macros:
offset_of! for obtaining the offset of a member of a struct.offset_of_tuple! for obtaining the offset of a member of a tuple. (Requires Rust 1.20+)offset_of_union! for obtaining the offset of a member of a union.span_of! for obtaining the range that a field, or fields, span.memoffset works under no_std environments.
Add the following dependency to your Cargo.toml:
[dependencies] memoffset = "0.8"
These versions will compile fine with rustc versions greater or equal to 1.19.
use memoffset::{offset_of, span_of}; #[repr(C, packed)] struct Foo { a: u32, b: u32, c: [u8; 5], d: u32, } fn main() { assert_eq!(offset_of!(Foo, b), 4); assert_eq!(offset_of!(Foo, d), 4+4+5); assert_eq!(span_of!(Foo, a), 0..4); assert_eq!(span_of!(Foo, a .. c), 0..8); assert_eq!(span_of!(Foo, a ..= c), 0..13); assert_eq!(span_of!(Foo, ..= d), 0..17); assert_eq!(span_of!(Foo, b ..), 4..17); }
memoffset has support for compile-time offset_of! on rust>=1.65, or on older nightly compilers.
Constant evaluation is automatically enabled and avilable on stable compilers starting with rustc 1.65.
This is an incomplete implementation with one caveat: Due to dependence on #![feature(const_refs_to_cell)], you cannot get the offset of a Cell field in a const-context.
This means that if need to get the offset of a cell, you'll have to remain on nightly for now.
If you‘re using a new-enough nightly and you require the ability to get the offset of a Cell, you’ll have to enable the unstable_const cargo feature, as well as enabling const_refs_to_cell in your crate root.
Do note that unstable_const is an unstable feature that is set to be removed in a future version of memoffset.
Cargo.toml:
[dependencies.memoffset] version = "0.8" features = ["unstable_const"]
Your crate root: (lib.rs/main.rs)
#![feature(const_refs_to_cell)]
In order to use it on an older nightly compiler, you must enable the unstable_const crate feature and several compiler features.
Your crate root: (lib.rs/main.rs)
#![feature(const_ptr_offset_from, const_refs_to_cell)]