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diff --git a/third_party/rust/memoffset-0.5.1/README.md b/third_party/rust/memoffset-0.5.1/README.md new file mode 100644 index 0000000000..9b64e87b3a --- /dev/null +++ b/third_party/rust/memoffset-0.5.1/README.md @@ -0,0 +1,54 @@ +# memoffset # + +[](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. + * `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 = "0.3" +``` + +Versions ">= 0.3" can be used in a constant expression context (though not in a `const fn`), +but require a rust version greater than or equal to 1.33. +These versions will compile fine with rustc versions greater or equal to 1.19, but will +lack support for constant expression. + +If you wish to use an older rustc version, lock your dependency to "0.2" + +Add the following lines at the top of your `main.rs` or `lib.rs` files. + +```rust +#[macro_use] +extern crate memoffset; +``` + +## Examples ## +```rust +#[repr(C, packed)] +struct Foo { + a: u32, + b: u32, + c: [u8; 5], + d: u32, +} + +assert_eq!(offset_of!(Foo, b), 4); +assert_eq!(offset_of!(Foo, c[3]), 11); + +assert_eq!(span_of!(Foo, a), 0..4); +assert_eq!(span_of!(Foo, a .. c), 0..8); +assert_eq!(span_of!(Foo, a .. c[1]), 0..9); +assert_eq!(span_of!(Foo, a ..= c[1]), 0..10); +assert_eq!(span_of!(Foo, ..= d), 0..14); +assert_eq!(span_of!(Foo, b ..), 4..17); +``` |