| commit | b5f85522935979fb380102750c07805edcc663f2 | [log] [tgz] |
|---|---|---|
| author | James Farrell <[email protected]> | Wed Sep 06 08:04:26 2023 +0000 |
| committer | Automerger Merge Worker <[email protected]> | Wed Sep 06 08:04:26 2023 +0000 |
| tree | 55e17a784a4f68296477f1a8138cd16288ac2592 | |
| parent | d98d022c5b18a064cb1849853e1b4bf731257e82 [diff] | |
| parent | 6146b87f3238258f52b7f32b370989b3ef8586ef [diff] |
Upgrade memoffset to 0.9.0 am: 6146b87f32 Original change: https://android-review.googlesource.com/c/platform/external/rust/crates/memoffset/+/2741828 Change-Id: I333be5acd97ada598d27aa57ee2a46eeaed75e18 Signed-off-by: Automerger Merge Worker <[email protected]>
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)]