Like Cow<'a, [u8]>, but with reference-counted bytes::Bytes instead of an owned Vec<u8>.
pub enum CowBytes<'a> {
Borrowed(&'a [u8]),
Shared(Bytes),
}Unlike Cow<'a, [u8]>, cloning and slicing a non-borrowed value are reference count operations rather than copies.
Unlike Bytes, which can only borrow &'static data, an arbitrary slice can be held without copying it, at the cost of a lifetime.
use cowbytes::CowBytes;
// Borrowing does not allocate.
let borrowed: CowBytes<'_> = CowBytes::from(&[1u8, 2, 3][..]);
// A `Vec` is adopted without copying.
let shared: CowBytes<'_> = CowBytes::from(vec![1u8, 2, 3]);
// Equality is by contents, not by variant.
assert_eq!(borrowed, shared);
// Slicing shared bytes keeps the same allocation.
let sliced: CowBytes<'_> = shared.slice(1..3);
assert_eq!(sliced, [2u8, 3]);
// `into_vec` hands the allocation back while it is unshared, rather than copying.
let bytes = vec![1u8, 2, 3];
let ptr = bytes.as_ptr();
let owned: Vec<u8> = CowBytes::from(bytes).into_vec();
assert_eq!(owned.as_ptr(), ptr);std(default) — enablesbytes/std. Disable forno_std(requiresalloc).serde— implementsSerializeandDeserialize. Add#[serde(borrow)]to struct fields holdingCowBytes<'a>to allow zero-copy deserialization from input data.
Licensed under either of
- Apache Licence, Version 2.0 (LICENSE-APACHE or http://www.apache.org/licenses/LICENSE-2.0)
- MIT Licence (LICENSE-MIT or http://opensource.org/licenses/MIT)
at your option.
