| commit | 405bbe8702de6ffe3d2f4e7fb04ea28b05fafb06 | [log] [tgz] |
|---|---|---|
| author | android-build-team Robot <[email protected]> | Wed Feb 17 04:32:44 2021 +0000 |
| committer | Automerger Merge Worker <[email protected]> | Wed Feb 17 04:32:44 2021 +0000 |
| tree | 6216aa665664884323b13a56a219df7056747f08 | |
| parent | c5d386103783f3d2b12df43eaa6143dc9c6631f2 [diff] | |
| parent | 15a3f727a3197d564d59a7f8c1d77219b6dfac20 [diff] |
Snap for 7149879 from 55a2790e869b1f95500f509783db169f783298aa to sc-release am: 15a3f727a3 Original change: https://googleplex-android-review.googlesource.com/c/platform/external/rust/crates/memoffset/+/13593958 MUST ONLY BE SUBMITTED BY AUTOMERGER Change-Id: I870518564ac5e70b3997e9dd875e76adf4153e43
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+)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 = "0.6"
These versions will compile fine with rustc versions greater or equal to 1.19.
Add the following lines at the top of your main.rs or lib.rs files.
#[macro_use] extern crate memoffset;
#[macro_use] extern crate memoffset; #[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 experimental support for compile-time offset_of! on a nightly compiler.
In order to use it, you must enable the unstable_const crate feature and several compiler features.
Cargo.toml:
[dependencies.memoffset] version = "0.6" features = ["unstable_const"]
Your crate root: (lib.rs/main.rs)
#![feature(ptr_offset_from, const_ptr_offset_from, const_maybe_uninit_as_ptr, const_raw_ptr_deref)]
If you intend to use offset_of! inside a const fn, also add the const_fn compiler feature.
Recent nightlies support a way to create raw pointers that avoids creating intermediate safe references. memoffset can make use of that feature to avoid what is technically Undefined Behavior. Use the unstable_raw feature to enable this.