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Diffstat (limited to 'rust/qemu-api/src/offset_of.rs')
| -rw-r--r-- | rust/qemu-api/src/offset_of.rs | 168 |
1 files changed, 0 insertions, 168 deletions
diff --git a/rust/qemu-api/src/offset_of.rs b/rust/qemu-api/src/offset_of.rs deleted file mode 100644 index 373229b..0000000 --- a/rust/qemu-api/src/offset_of.rs +++ /dev/null @@ -1,168 +0,0 @@ -// SPDX-License-Identifier: MIT - -#![doc(hidden)] -//! This module provides macros that emulate the functionality of -//! `core::mem::offset_of` on older versions of Rust. -//! -//! Documentation is hidden because it only exposes macros, which -//! are exported directly from `qemu_api`. - -/// This macro provides the same functionality as `core::mem::offset_of`, -/// except that only one level of field access is supported. The declaration -/// of the struct must be wrapped with `with_offsets! { }`. -/// -/// It is needed because `offset_of!` was only stabilized in Rust 1.77. -#[cfg(not(has_offset_of))] -#[macro_export] -macro_rules! offset_of { - ($Container:ty, $field:ident) => { - <$Container>::OFFSET_TO__.$field - }; -} - -/// A wrapper for struct declarations, that allows using `offset_of!` in -/// versions of Rust prior to 1.77 -#[macro_export] -macro_rules! with_offsets { - // This method to generate field offset constants comes from: - // - // https://play.rust-lang.org/?version=stable&mode=debug&edition=2018&gist=10a22a9b8393abd7b541d8fc844bc0df - // - // used under MIT license with permission of Yandros aka Daniel Henry-Mantilla - ( - $(#[$struct_meta:meta])* - $struct_vis:vis - struct $StructName:ident { - $( - $(#[$field_meta:meta])* - $field_vis:vis - $field_name:ident : $field_ty:ty - ),* - $(,)? - } - ) => ( - #[cfg(not(has_offset_of))] - const _: () = { - struct StructOffsetsHelper<T>(std::marker::PhantomData<T>); - const END_OF_PREV_FIELD: usize = 0; - - // populate StructOffsetsHelper<T> with associated consts, - // one for each field - $crate::with_offsets! { - @struct $StructName - @names [ $($field_name)* ] - @tys [ $($field_ty ,)*] - } - - // now turn StructOffsetsHelper<T>'s consts into a single struct, - // applying field visibility. This provides better error messages - // than if offset_of! used StructOffsetsHelper::<T> directly. - pub - struct StructOffsets { - $( - $field_vis - $field_name: usize, - )* - } - impl $StructName { - pub - const OFFSET_TO__: StructOffsets = StructOffsets { - $( - $field_name: StructOffsetsHelper::<$StructName>::$field_name, - )* - }; - } - }; - ); - - ( - @struct $StructName:ident - @names [] - @tys [] - ) => (); - - ( - @struct $StructName:ident - @names [$field_name:ident $($other_names:tt)*] - @tys [$field_ty:ty , $($other_tys:tt)*] - ) => ( - #[allow(non_local_definitions)] - #[allow(clippy::modulo_one)] - impl StructOffsetsHelper<$StructName> { - #[allow(nonstandard_style)] - const $field_name: usize = { - const ALIGN: usize = std::mem::align_of::<$field_ty>(); - const TRAIL: usize = END_OF_PREV_FIELD % ALIGN; - END_OF_PREV_FIELD + (if TRAIL == 0 { 0usize } else { ALIGN - TRAIL }) - }; - } - const _: () = { - const END_OF_PREV_FIELD: usize = - StructOffsetsHelper::<$StructName>::$field_name + - std::mem::size_of::<$field_ty>() - ; - $crate::with_offsets! { - @struct $StructName - @names [$($other_names)*] - @tys [$($other_tys)*] - } - }; - ); -} - -#[cfg(test)] -mod tests { - use crate::offset_of; - - #[repr(C)] - struct Foo { - a: u16, - b: u32, - c: u64, - d: u16, - } - - #[repr(C)] - struct Bar { - pub a: u16, - pub b: u64, - c: Foo, - d: u64, - } - - crate::with_offsets! { - #[repr(C)] - struct Bar { - pub a: u16, - pub b: u64, - c: Foo, - d: u64, - } - } - - #[repr(C)] - pub struct Baz { - b: u32, - a: u8, - } - crate::with_offsets! { - #[repr(C)] - pub struct Baz { - b: u32, - a: u8, - } - } - - #[test] - fn test_offset_of() { - const OFFSET_TO_C: usize = offset_of!(Bar, c); - - assert_eq!(offset_of!(Bar, a), 0); - assert_eq!(offset_of!(Bar, b), 8); - assert_eq!(OFFSET_TO_C, 16); - assert_eq!(offset_of!(Bar, d), 40); - - assert_eq!(offset_of!(Baz, b), 0); - assert_eq!(offset_of!(Baz, a), 4); - } -} |