Re: [PATCH 1/5] refs: store submodule ref stores in a hashmap

On 02/09/2017 09:34 PM, Junio C Hamano wrote:

Michael Haggerty [off-list ref] writes:

quoted

[...]
+static int submodule_hash_cmp(const void *entry, const void *entry_or_key,
+			      const void *keydata)
+{
+	const struct submodule_hash_entry *e1 = entry, *e2 = entry_or_key;
+	const char *submodule = keydata;
+
+	return strcmp(e1->submodule, submodule ? submodule : e2->submodule);

I would have found it more readable if it were like so:

	const char *submodule = keydata ? keydata : e2->submodule;

	return strcmp(e1->submodule, submodule);

but I suspect the difference is not that huge.

Yes, that's better. I'll change it.

On 02/10/2017 05:04 AM, Jeff King wrote:

On Thu, Feb 09, 2017 at 12:34:04PM -0800, Junio C Hamano wrote:

quoted

quoted

+static struct submodule_hash_entry *alloc_submodule_hash_entry(
+		const char *submodule, struct ref_store *refs)
+{
+	size_t len = strlen(submodule);
+	struct submodule_hash_entry *entry = malloc(sizeof(*entry) + len + 1);

I think this (and the later memcpy) is what FLEX_ALLOC_MEM() was
invented for.

Yes, it was. Though since the length comes from a strlen() call, it can
actually use the _STR variant, like:

  FLEX_ALLOC_STR(entry, submodule, submodule);

Besides being shorter, this does integer-overflow checks on the final
length.

Nice. TIL. Will fix.

quoted

quoted

@@ -1373,16 +1405,17 @@ void base_ref_store_init(struct ref_store *refs,
 			die("BUG: main_ref_store initialized twice");

 		refs->submodule = "";
-		refs->next = NULL;
 		main_ref_store = refs;
 	} else {
-		if (lookup_ref_store(submodule))
+		refs->submodule = xstrdup(submodule);
+
+		if (!submodule_ref_stores.tablesize)
+			hashmap_init(&submodule_ref_stores, submodule_hash_cmp, 20);

Makes me wonder what "20" stands for.  Perhaps the caller should be
allowed to say "I do not quite care what initial size is" by passing
0 or some equally but more clealy meaningless value (which of course
would be outside the scope of this series).

I think this is what "0" already does (grep for HASHMAP_INITIAL_SIZE).
In fact, that constant is 64. The 20 we pass in goes through some magic
load-factor computation and ends up as 25. That being smaller than the
INITIAL_SIZE constant, I believe that we end up allocating 64 entries
either way (that's just from reading the code, though; I didn't run it
to double check).

I guess I might as well change it to zero, then.

Thanks for the feedback!

Michael