diff options
Diffstat (limited to 'vendor/memoffset/README.md')
-rw-r--r-- | vendor/memoffset/README.md | 65 |
1 files changed, 65 insertions, 0 deletions
diff --git a/vendor/memoffset/README.md b/vendor/memoffset/README.md new file mode 100644 index 000000000..9e93c2bcc --- /dev/null +++ b/vendor/memoffset/README.md @@ -0,0 +1,65 @@ +# 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+) + * `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 = "0.6" +``` + +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); +} +``` + +## Feature flags ## + +### Usage in constants ### +`memoffset` has **experimental** support for compile-time `offset_of!` on a nightly compiler. + +In order to use it, you must enable the `unstable_const` crate feature and several compiler features. + +Cargo.toml: +```toml +[dependencies.memoffset] +version = "0.6" +features = ["unstable_const"] +``` + +Your crate root: (`lib.rs`/`main.rs`) +```rust,ignore +#![feature(const_ptr_offset_from, const_refs_to_cell)] +``` |