61 lines
3.0 KiB
Markdown
61 lines
3.0 KiB
Markdown
* **[Latest Docs.rs Here](https://docs.rs/bytemuck/)**
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[](https://opensource.org/licenses/Zlib)
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[](https://crates.io/crates/bytemuck)
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# bytemuck
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A crate for mucking around with piles of bytes.
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This crate lets you safely perform "bit cast" operations between data types.
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That's where you take a value and just reinterpret the bits as being some other
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type of value, without changing the bits.
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* This is **not** like the [`as` keyword][keyword-as]
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* This is **not** like the [`From` trait][from-trait]
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* It is **most like** [`f32::to_bits`][f32-to_bits], just generalized to let you
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convert between all sorts of data types.
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[keyword-as]: https://doc.rust-lang.org/nightly/std/keyword.as.html
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[from-trait]: https://doc.rust-lang.org/nightly/core/convert/trait.From.html
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[f32-to_bits]: https://doc.rust-lang.org/nightly/std/primitive.f32.html#method.to_bits
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### Here's the part you're more likely to care about: *you can do this with slices too!*
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When a slice is involved it's not a *direct* bitcast. Instead, the `cast_slice`
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and `cast_slice_mut` functions will pull apart a slice's data and give you a new
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slice that's the same span of memory just viewed as the new type. If the size of
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the slice's element changes then the length of the slice you get back will be
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changed accordingly.
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This lets you cast a slice of color values into a slice of `u8` and send it to
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the GPU, or things like that. I'm sure there's other examples, but honestly this
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crate is as popular as it is mostly because of Rust's 3D graphics community
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wanting to cast slices of different types into byte slices for sending to the
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GPU. Hi friends! Push those vertices, or whatever it is that you all do.
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## See Also
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While `bytemuck` is full of unsafe code, I've also started a "sibling crate"
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called [bitfrob](https://docs.rs/bitfrob/latest/bitfrob/), which is where
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operations that are 100% safe will be added.
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## Stability
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* The crate is 1.0 and I consider this it to be "basically done". New features
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are usually being accepted when other people want to put in the work, but
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myself I wanna move on to using `bytemuck` in bigger projects.
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* The default build of the `bytemuck` crate will continue to work with `rustc-1.34`
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for at least the rest of the `1.y.z` versions.
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* Any other cargo features of the crate **are not** held to the same standard, and
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may work only on the latest Stable or even only on latest Nightly.
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**Future Plans:** Once the [Safe Transmute Project][pg-st] completes and
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stabilizes ("eventually") this crate will be updated to use that as the
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underlying mechanism for transmutation bounds, and a 2.0 version of `bytemuck`
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will be released. The hope is for the 1.0 to 2.0 transition to be as seamless as
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possible, but the future is always uncertain.
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[pg-st]: https://rust-lang.github.io/rfcs/2835-project-safe-transmute.html
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