Size Of No Padding

This crate provides two derive proc-macro.

SizeOfNoPadding

Only support struct can be marked as Copy

Create a shadow struct which as same as original struct except it's marked #[repr(packed)]. call size_of_no_padding() method on struct will invoke std::mem::size_of() function on shadow one in compile time.

Example

use size_of_no_padding::SizeOfNoPadding;
use size_of_no_padding::SizeOf;

#[derive(SizeOfNoPadding)]
struct Abc {
    a: u8,
    b: u32,
    c: u8,
}

assert_eq!(8, std::mem::size_of::<Abc>());
assert_eq!(6, Abc::size_of_no_padding());

SizeOfNoPaddingAny

Support struct whose non-Copy fields impl SizeOfAny trait

Calculate the size for every field, add up all the size. call size_of_no_padding(&self) will give the size of whole struct without padding in runtime.

Example

use size_of_no_padding::SizeOfNoPaddingAny;
use size_of_no_padding::SizeOfAny;

#[derive(SizeOfNoPaddingAny)]
struct Abc2 {
    a: u8,
    b: u32,
    c: u8,
    d: Vec<u16>,
    e: Abc3,
}

#[derive(SizeOfNoPaddingAny)]
struct Abc3([u32; 4], u16);

let abc = Abc2 {
    a: 1,
    b: 2,
    c: 3,
    d: vec![4, 5, 6],
    e: Abc3([7, 8, 9, 10], 11),
};

assert_eq!(std::mem::size_of::<Abc2>(), 56);
assert_eq!(abc.size_of_no_padding_any(), 30);

License

Licensed under either of

• Apache License, Version 2.0, (LICENSE-APACHE or http://www.apache.org/licenses/LICENSE-2.0)
• MIT license (LICENSE-MIT or http://opensource.org/licenses/MIT)

at your option.