| # 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 = "0.5" | |
| ``` | |
| These versions will compile fine with rustc versions greater or equal to 1.20. | |
| Add the following lines at the top of your `main.rs` or `lib.rs` files. | |
| ```rust,ignore | |
| #[macro_use] | |
| extern crate memoffset; | |
| ``` | |
| ## Examples ## | |
| ```rust | |
| #[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); | |
| } | |
| ``` |