| commit | b6a9bde57b904da167ee40ff14078fd7473b900d | [log] [tgz] |
|---|---|---|
| author | Android Build Coastguard Worker <[email protected]> | Wed Jun 15 21:44:37 2022 +0000 |
| committer | Android Build Coastguard Worker <[email protected]> | Wed Jun 15 21:44:37 2022 +0000 |
| tree | a7d702e71f38ae1597839c01ccca8820999c02e9 | |
| parent | 3c15a71a648e1a07b87943b033241ce688db3d39 [diff] | |
| parent | 746a9df534dfa538f6de73c5c206837590bed62f [diff] |
Snap for 8730993 from 746a9df534dfa538f6de73c5c206837590bed62f to mainline-tzdata3-release Change-Id: Iac00555866c3215b0e1f2e1ee5f1b497ca4fbf73
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.