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author | Daniel Baumann <daniel.baumann@progress-linux.org> | 2024-05-30 03:57:31 +0000 |
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committer | Daniel Baumann <daniel.baumann@progress-linux.org> | 2024-05-30 03:57:31 +0000 |
commit | dc0db358abe19481e475e10c32149b53370f1a1c (patch) | |
tree | ab8ce99c4b255ce46f99ef402c27916055b899ee /vendor/memoffset-0.8.0/README.md | |
parent | Releasing progress-linux version 1.71.1+dfsg1-2~progress7.99u1. (diff) | |
download | rustc-dc0db358abe19481e475e10c32149b53370f1a1c.tar.xz rustc-dc0db358abe19481e475e10c32149b53370f1a1c.zip |
Merging upstream version 1.72.1+dfsg1.
Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>
Diffstat (limited to 'vendor/memoffset-0.8.0/README.md')
-rw-r--r-- | vendor/memoffset-0.8.0/README.md | 85 |
1 files changed, 85 insertions, 0 deletions
diff --git a/vendor/memoffset-0.8.0/README.md b/vendor/memoffset-0.8.0/README.md new file mode 100644 index 000000000..b0bfd1014 --- /dev/null +++ b/vendor/memoffset-0.8.0/README.md @@ -0,0 +1,85 @@ +# memoffset # + +[![](https://img.shields.io/crates/v/memoffset.svg)](https://crates.io/crates/memoffset) + +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. + +## Usage ## +Add the following dependency to your `Cargo.toml`: + +```toml +[dependencies] +memoffset = "0.8" +``` + +These versions will compile fine with rustc versions greater or equal to 1.19. + +## Examples ## +```rust +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); +} +``` + +## Usage in constants ## +`memoffset` has support for compile-time `offset_of!` on rust>=1.65, or on older nightly compilers. + +### Usage on stable Rust ### +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)]`](https://github.com/rust-lang/rust/issues/80384), 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. + +### Usage on recent nightlies ### + +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: +```toml +[dependencies.memoffset] +version = "0.8" +features = ["unstable_const"] +``` + +Your crate root: (`lib.rs`/`main.rs`) +```rust,ignore +#![feature(const_refs_to_cell)] +``` + +### Usage on older nightlies ### +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`) +```rust,ignore +#![feature(const_ptr_offset_from, const_refs_to_cell)] +``` |