Bind HashMap::reserve() to Dictionary

[dementive]

Describe the project you are working on

Prototyping a game.

Describe the problem or limitation you are having in your project

Currently Dictionary has no way to reserve a know amount of memory, but HashMap does with the reserve() function.

Describe the feature / enhancement and how it helps to overcome the problem or limitation

Currently when inserting a large number of elements into an Array the ideal way to do it would be to first resize and then add elements instead of just using push_back. Dictionary should be able to do the same thing. Adding the reserve method to Dictionary would make it so you can avoid a ton unnecessary memory allocations and rehashes in languages outside of C++, where you can’t just use HashMap directly. Not reserving memory for the HashMap is probably worse than not doing it for Array too since it mallocs a new block of memory and copies the old data in on every resize instead of reallocing like Array does.

Describe how your proposal will work, with code, pseudo-code, mock-ups, and/or diagrams

Should be simple to add just bind the method in Dictionary and have it call the reserve method from it’s DictionaryPrivate then write some documentation and maybe add a test. I could write the code to do it if approved.

If this enhancement will not be used often, can it be worked around with a few lines of script?

No.

Is there a reason why this should be core and not an add-on in the asset library?

Not possible.

[Calinou]

• Related to Add capacity() and reserve() to core data structures #2954.

[Ivorforce]

GDScript has a lot of overhead, so not all functions that are important in C++ are important in GDScript. Before exposing reserve, we should measure whether it makes an important enough difference to warrant the additional complexity for GDScript users.

(Although, I suppose, it may still be worth it for C++ and Rust users, where it will definitely make a large difference)