refs: track ref stores via strmap

The refs code has two global maps that track the submodule and worktree
ref stores. Even though both of these maps track values by strings, we
still use a `struct hashmap` instead of a `struct strmap`. This has the
benefit of saving us an allocation because we can combine key and value
in a single struct. But it does introduce significant complexity that is
completely unneeded.

Refactor the code to use `struct strmap`s instead to reduce complexity.
It's unlikely that this will have any real-world impact on performance
given that most repositories likely won't have all that many ref stores.
Furthermore, this refactoring allows us to de-globalize those maps and
move them into `struct repository` in a subsequent commit more easily.

Signed-off-by: Patrick Steinhardt <[email protected]>
Signed-off-by: Junio C Hamano <[email protected]>

Author: pks-t

refs.c

@@ -6,7 +6,7 @@
 #include "advice.h"
 #include "config.h"
 #include "environment.h"
-#include "hashmap.h"
+#include "strmap.h"
 #include "gettext.h"
 #include "hex.h"
 #include "lockfile.h"
@@ -1960,66 +1960,27 @@ int resolve_gitlink_ref(const char *submodule, const char *refname,
 	return 0;
 }
 
-struct ref_store_hash_entry
-{
-	struct hashmap_entry ent;
-
-	struct ref_store *refs;
-
-	/* NUL-terminated identifier of the ref store: */
-	char name[FLEX_ARRAY];
-};
+/* A strmap of ref_stores, stored by submodule name: */
+static struct strmap submodule_ref_stores;
 
-static int ref_store_hash_cmp(const void *cmp_data UNUSED,
-			      const struct hashmap_entry *eptr,
-			      const struct hashmap_entry *entry_or_key,
-			      const void *keydata)
-{
-	const struct ref_store_hash_entry *e1, *e2;
-	const char *name;
-
-	e1 = container_of(eptr, const struct ref_store_hash_entry, ent);
-	e2 = container_of(entry_or_key, const struct ref_store_hash_entry, ent);
-	name = keydata ? keydata : e2->name;
-
-	return strcmp(e1->name, name);
-}
-
-static struct ref_store_hash_entry *alloc_ref_store_hash_entry(
-		const char *name, struct ref_store *refs)
-{
-	struct ref_store_hash_entry *entry;
-
-	FLEX_ALLOC_STR(entry, name, name);
-	hashmap_entry_init(&entry->ent, strhash(name));
-	entry->refs = refs;
-	return entry;
-}
-
-/* A hashmap of ref_stores, stored by submodule name: */
-static struct hashmap submodule_ref_stores;
-
-/* A hashmap of ref_stores, stored by worktree id: */
-static struct hashmap worktree_ref_stores;
+/* A strmap of ref_stores, stored by worktree id: */
+static struct strmap worktree_ref_stores;
 
 /*
  * Look up a ref store by name. If that ref_store hasn't been
  * registered yet, return NULL.
  */
-static struct ref_store *lookup_ref_store_map(struct hashmap *map,
+static struct ref_store *lookup_ref_store_map(struct strmap *map,
 					      const char *name)
 {
-	struct ref_store_hash_entry *entry;
-	unsigned int hash;
+	struct strmap_entry *entry;
 
-	if (!map->tablesize)
+	if (!map->map.tablesize)
 		/* It's initialized on demand in register_ref_store(). */
 		return NULL;
 
-	hash = strhash(name);
-	entry = hashmap_get_entry_from_hash(map, hash, name,
-					struct ref_store_hash_entry, ent);
-	return entry ? entry->refs : NULL;
+	entry = strmap_get_entry(map, name);
+	return entry ? entry->value : NULL;
 }
 
 /*
@@ -2064,18 +2025,14 @@ struct ref_store *get_main_ref_store(struct repository *r)
  * Associate a ref store with a name. It is a fatal error to call this
  * function twice for the same name.
  */
-static void register_ref_store_map(struct hashmap *map,
+static void register_ref_store_map(struct strmap *map,
 				   const char *type,
 				   struct ref_store *refs,
 				   const char *name)
 {
-	struct ref_store_hash_entry *entry;
-
-	if (!map->tablesize)
-		hashmap_init(map, ref_store_hash_cmp, NULL, 0);
-
-	entry = alloc_ref_store_hash_entry(name, refs);
-	if (hashmap_put(map, &entry->ent))
+	if (!map->map.tablesize)
+		strmap_init(map);
+	if (strmap_put(map, name, refs))
 		BUG("%s ref_store '%s' initialized twice", type, name);
 }