The OrderedHash PMC provides indexed access by a (string) key as well as
indexed access by insertion order. It's currently implemented as an hash
holding the index value into the data array.
The problem is of course deleting items (and adding items w/o string
key). The former is done by storing a new Undef item, the latter just
messes up the whole thing, IIRC.
Anyway, we can achieve the same effect by indexing into the hash bucket
store directly (at least after reversing the free_list order).
E.g. an (ordered) hash with 4 entries, these are hashed in the bucket
index and point to the bucket store:
buckets keys (bucket**)
b0 b1 b2 b3 h2 h1 h3 h0
The buckets just come in order from the free_list - or for the
specialized ordered hash - are just given away in array indexed order.
This would suffice for the planned used cases, which are typically:
- add (push) items by key
- retrieve items by key or by numeric index
E.g.:
- lexicals
- PMC/class types
- object attributes
- constant string table
- ...
leo
