#transmute #bytes #casting

no-std bytemuck

A crate for mucking around with piles of bytes

17 stable releases

new 1.12.0 Aug 14, 2022
1.11.0 Jul 24, 2022
1.9.1 Apr 2, 2022
1.9.0 Mar 30, 2022
0.1.2 Nov 11, 2019

#24 in Encoding

Download history 144016/week @ 2022-04-26 137913/week @ 2022-05-03 136435/week @ 2022-05-10 132690/week @ 2022-05-17 125153/week @ 2022-05-24 134571/week @ 2022-05-31 142939/week @ 2022-06-07 146524/week @ 2022-06-14 170017/week @ 2022-06-21 174492/week @ 2022-06-28 177461/week @ 2022-07-05 186866/week @ 2022-07-12 170021/week @ 2022-07-19 171051/week @ 2022-07-26 178682/week @ 2022-08-02 180192/week @ 2022-08-09

731,551 downloads per month
Used in 2,903 crates (361 directly)

Zlib OR Apache-2.0 OR MIT

125KB
1.5K SLoC

License:Zlib Minimum Rust Version crates.io

bytemuck

A crate for mucking around with piles of bytes.

This crate lets you safely perform "bit cast" operations between data types. That's where you take a value and just reinterpret the bits as being some other type of value, without changing the bits.

  • This is not like the as keyword
  • This is not like the From trait
  • It is most like f32::to_bits, just generalized to let you convert between all sorts of data types.

Here's the part you're more likely to care about: you can do this with slices too!

When a slice is involved it's not a direct bitcast. Instead, the cast_slice and cast_slice_mut functions will pull apart a slice's data and give you a new slice that's the same span of memory just viewed as the new type. If the size of the slice's element changes then the length of the slice you get back will be changed accordingly.

This lets you cast a slice of color values into a slice of u8 and send it to the GPU, or things like that. I'm sure there's other examples, but honestly this crate is as popular as it is mostly because of Rust's 3D graphics community wanting to cast slices of different types into byte slices for sending to the GPU. Hi friends! Push those vertices, or whatever it is that you all do.

See Also

While bytemuck is full of unsafe code, I've also started a "sibling crate" called bitfrob, which is where operations that are 100% safe will be added.

Stability

  • The crate is 1.0 and I consider this it to be "basically done". New features are usually being accepted when other people want to put in the work, but myself I wanna move on to using bytemuck in bigger projects.
  • The core of the bytemuck crate will continue to work with rustc-1.34 for at least the rest of the 1.y.z versions.
  • Opt-in features of the crate are not held to the same standard, and may work only on the latest Stable or latest Nightly.

Future Plans: Once the Safe Transmute Project completes and stabilizes ("eventually") this crate will be updated to use that as the underlying mechanism for transmutation bounds, and a 2.0 version of bytemuck will be released. The hope is for the 1.0 to 2.0 transition to be as seamless as possible, but the future is always uncertain.

Dependencies