hashmap: add disallow_rehash setting

[thirdparty/git.git] / hashmap.h

diff --git a/hashmap.h b/hashmap.h
index 45eda693bdbc7efc53f6b0ce29a172bcb574cfdf..de6022a3a916605d8e3330b23259110dd3522c7d 100644 (file)
--- a/hashmap.h
+++ b/hashmap.h
@@ -39,6 +39,7 @@ struct hashmap {
        struct hashmap_entry **table;
        hashmap_cmp_fn cmpfn;
        unsigned int size, tablesize, grow_at, shrink_at;
+       unsigned disallow_rehash : 1;
 };
 
 struct hashmap_iter {
@@ -77,6 +78,29 @@ static inline void *hashmap_get_from_hash(const struct hashmap *map,
        return hashmap_get(map, &key, keydata);
 }
 
+int hashmap_bucket(const struct hashmap *map, unsigned int hash);
+
+/*
+ * Disallow/allow rehashing of the hashmap.
+ * This is useful if the caller knows that the hashmap
+ * needs multi-threaded access.  The caller is still
+ * required to guard/lock searches and inserts in a
+ * manner appropriate to their usage.  This simply
+ * prevents the table from being unexpectedly re-mapped.
+ *
+ * If is up to the caller to ensure that the hashmap is
+ * initialized to a reasonable size to prevent poor
+ * performance.
+ *
+ * When value=1, prevent future rehashes on adds and deleted.
+ * When value=0, allow future rehahses.  This DOES NOT force
+ * a rehash now.
+ */
+static inline void hashmap_disallow_rehash(struct hashmap *map, unsigned value)
+{
+       map->disallow_rehash = value;
+}
+
 /* hashmap_iter functions */
 
 extern void hashmap_iter_init(struct hashmap *map, struct hashmap_iter *iter);