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offsetof for Rust
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README.md

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:

[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.

#[macro_use]
extern crate memoffset;

Examples

#[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);
}
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