#alloc #buffer #reuse #memory #types #data

no-std same-alloc

Reuse an allocated buffer for data with different types

1 release (0 unstable)

1.0.0-alpha Mar 16, 2021

MIT OR Apache-2.0 OR Zlib

13KB
151 lines

The SameVec makes it possible to re-use allocations across multiple invocations of zero-copy parsers.

This crate provides an allocated buffer that can be used by vectors of different element types, as long as they have the same layout. Most prominently this allows use of one buffer where the element type depends on a function local lifetime. The required vector type would be impossible to name outside the function.

fn select_median_name(unparsed: &str) -> &str {
    // Problem: This type depends on the lifetime parameter. Ergo, we can not normally store _one_
    // vector in the surrounding function, and instead need to allocate here a new one.
    let mut names: Vec<_> = unparsed.split(' ').collect();
    let idx = names.len() / 2;
    *names.select_nth_unstable(idx).1
}

fn select_median_name_with_buffer<'names>(
    unparsed: &'names str,
    buf: &mut SameVec<*const str>,
) -> &'names str {
    let mut names = buf.use_for(same::for_ref());
    names.extend(unparsed.split(' '));
    let idx = names.len() / 2;
    *names.select_nth_unstable(idx).1
}

License

This project is licensed under Zlib OR Apache-2.0 OR MIT. You may alternatively choose the Unlicense instead in which case the copyright headers signify the parts dedicated to the public domain to the fullest possible extent instead.

No runtime deps