Issue #19236 has been updated by janosch-x (Janosch Müller).
maybe the genie is out of the bottle already, but it would be nice to have a uniform API
for creating objects with a given capacity, e.g.
```ruby
Array.with_capacity(100) # => []
Hash.with_capacity(100) # => {}
IO::Buffer.with_capacity(100) # => #<IO::Buffer>
String.with_capacity(100) # => ''
# more?
```
for `Array` and `IO::Buffer`, `::with_capacity` would essentially be an alias for `::new`.
for `String`, the `capacity` kwarg could be deprecated to limit the number of APIs.
----------------------------------------
Feature #19236: Allow to create hashes with a specific capacity from Ruby
https://bugs.ruby-lang.org/issues/19236#change-100797
* Author: byroot (Jean Boussier)
* Status: Open
* Priority: Normal
* Target version: 3.3
----------------------------------------
Followup on [Feature #18683] which added a C-API for this purpose.
Various protocol parsers such as Redis `RESP3` or `msgpack`, have to create hashes, and
they know the size in advance.
For efficiency, it would be preferable if they could directly allocate a Hash of the
necessary size, so that large hashes wouldn't cause many re-alloccations and
re-hash.
`String` and `Array` both already offer similar APIs:
```ruby
String.new(capacity: XXX)
Array.new(XX) / rb_ary_new_capa(long)
```
However there's no such public API for Hashes in Ruby land.
### Proposal
I think `Hash` should have a way to create a new hash with a `capacity` parameter.
The logical signature of `Hash.new(capacity: 1000)` was deemed too incompatible in
[Feature #18683].
@Eregon proposed to add `Hash.create(capacity: 1000)`.
--
https://bugs.ruby-lang.org/