583729 - js hashtable - ability to reserve

Status: RESOLVED INCOMPLETE

(Core :: JavaScript Engine, enhancement)

Description

[Igor Bukanov]

It would be nice to add to HashTable and HashSet a method similar to Vector::reserve that would guarantee that the following additions to the table would always succeed. The current init method allows to do that only during initialization which is insufficient.

Comment 1

[Luke Wagner [:luke]]

One problem is that if reserve simply makes the table bigger, and the user does a remove before reaching the reserved size, then checkUnderloaded would shrink the table back down.

Comment 2

[Igor Bukanov]

(In reply to comment #1)
> One problem is that if reserve simply makes the table bigger, and the user does
> a remove before reaching the reserved size, then checkUnderloaded would shrink
> the table back down.

This is fine as my use case is to avoid writing the release operation in code like:

key = prepare_key();
if (!key)
    return false;
if (!hashtable.put(key, value)) {
    release_key(key);
    return false;
}

With reserve that would be 

if (!hashtable.reserve(length() + 1))
    return false;
key = prepare_key();
if (!key)
    return false;
hashtable.put(key, value);