Crate bumpish 

bumpish

A set of collections that use bump allocations under the hood. For now there are three collections in this crate:

• BumpMap — hash map.
• BumpSet — hash set.
• BumpVec — vector.

What is bump allocation?

Bump allocation is another way to allocate memory for data types collecting elements, like vectors and lists. If vectors contain elements in a single continuous chunk of memory, and lists allocate a little chunk for every element, collections, that use bump allocation, are a cross between these two approaches. They allocate relatively big chunks of memory where put new elements sequentially.

- Vector collection
  ╭───┬───┬───┬───┬───┬───┬───┬───┬───┬───┬─────╮
  │ 0 │ 1 │ 2 │ 3 │ 4 │ 5 │ 6 │ 7 │ 8 │ 9 │ ... │
  ╰───┴───┴───┴───┴───┴───┴───┴───┴───┴───┴─────╯
- List collection
  ╭───╮ ╭───╮ ╭───╮ ╭───╮ ╭───╮ ╭───╮ ╭───╮ ╭───╮ ╭───╮ ╭───╮ ╭───╮
  │ 0 │↔│ 1 │↔│ 2 │↔│ 3 │↔│ 4 │↔│ 5 │↔│ 6 │↔│ 7 │↔│ 8 │↔│ 9 │↔│...│
  ╰───╯ ╰───╯ ╰───╯ ╰───╯ ╰───╯ ╰───╯ ╰───╯ ╰───╯ ╰───╯ ╰───╯ ╰───╯
- Bump collection
  ╭───┬───╮ ╭───┬───┬───┬───╮ ╭───┬───┬───┬───┬─────╮
  │ 0 │ 1 │↔│ 2 │ 3 │ 4 │ 5 │↔│ 6 │ 7 │ 8 │ 9 │ ... │
  ╰───┴───╯ ╰───┴───┴───┴───╯ ╰───┴───┴───┴───┴─────╯

In contrast to vectors, bump collections don’t move elements from an old memory chunk to a new one when the chunk fills up. Instead, leave the old one untouched, and continue pushing new elements into the new chunk.

When should I use bimpish collections instead of bumpalo?

If you want elements’ Drop implementations to be invoked during deallocation.

When should I use bumpish collections instead of standard collections?

Collections from the standard library can grow only by a mutable reference to themeselves. The reason is that they need to reallocate memory when the chunk fills up, which invalidates all existing references. In contrast, bump collections do not invalidate references, because they just push new elements onto the end of a new chunk. So adding new elements are done using a shared reference to bump collections.

So, if you have a structure that only grows, and you have to use a RefCell wrapper around it to get a mutable reference to it, bumpish collections can improve ergonomics of your code.

Re-exports

pub use map::BumpMap;

pub use set::BumpSet;

pub use vec::BumpVec;

Modules

map

BumpMap

set

BumpSet

vec

BumpVec