Re: [PATCH v2 01/16] hashtable: introduce a small and naive hashtable

On 08/19/2012 04:16 PM, Mathieu Desnoyers wrote:

* Mathieu Desnoyers (mathieu.desnoyers-vg+e7yoeK/dWk0Htik3J/w@public.gmane.org) wrote:

quoted

* Sasha Levin (levinsasha928-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org) wrote:

[...]

quoted

quoted

+/**
+ * hash_for_each_possible - iterate over all possible objects for a given key
+ * @name: hashtable to iterate
+ * @obj: the type * to use as a loop cursor for each bucket
+ * @bits: bit count of hashing function of the hashtable
+ * @node: the &struct list_head to use as a loop cursor for each bucket
+ * @member: the name of the hlist_node within the struct
+ * @key: the key of the objects to iterate over
+ */
+#define hash_for_each_possible_size(name, obj, bits, node, member, key)		\
+	hlist_for_each_entry(obj, node,	&name[hash_min(key, bits)], member)

Second point: "for_each_possible" does not express the iteration scope.
Citing WordNet: "possible adj 1: capable of happening or existing;" --
which has nothing to do with iteration on duplicate keys within a hash
table.

I would recommend to rename "possible" to "duplicate", e.g.:

  hash_for_each_duplicate()

which clearly says what is the scope of this iteration: duplicate keys.

OK, about this part: I now see that you iterate over all objects within
the same hash chain. I guess the description "iterate over all possible
objects for a given key" is misleading: it's not all objects with a
given key, but rather all objects hashing to the same bucket.

I understand that you don't want to build knowledge of the key
comparison function in the iterator (which makes sense for a simple hash
table).

By the way, the comment "@obj: the type * to use as a loop cursor for
each bucket" is also misleading: it's a loop cursor for each entry,
since you iterate on all nodes within single bucket. Same for "@node:
the &struct list_head to use as a loop cursor for each bucket".

So with these documentation changes applied, hash_for_each_possible
starts to make more sense, because it refers to entries that can
_possibly_ be a match (or not). Other options would be
hash_chain_for_each() or hash_bucket_for_each().

I'd rather avoid starting to use chain/bucket since they're not used anywhere
else (I've tried keeping internal hashing/bucketing opaque to the user).

Otherwise makes sense, I'll improve the documentation as suggested. Thanks!

Thanks,

Mathieu