hashmap: introduce hash_ops to make struct Hashmap smaller

It is redundant to store 'hash' and 'compare' function pointers in
struct Hashmap separately. The functions always comprise a pair.
Store a single pointer to struct hash_ops instead.

systemd keeps hundreds of hashmaps, so this saves a little bit of
memory.

1 files changed, 15 insertions, 3 deletions

diff --git a/src/shared/hashmap.h b/src/shared/hashmap.h
index f89e7e8fbc..7385ebc5fa 100644
--- a/src/shared/hashmap.h
+++ b/src/shared/hashmap.h
@@ -43,38 +43,50 @@ typedef _IteratorStruct* Iterator;
 typedef unsigned long (*hash_func_t)(const void *p, const uint8_t hash_key[HASH_KEY_SIZE]);
 typedef int (*compare_func_t)(const void *a, const void *b);
 
+struct hash_ops {
+        hash_func_t hash;
+        compare_func_t compare;
+};
+
 unsigned long string_hash_func(const void *p, const uint8_t hash_key[HASH_KEY_SIZE]) _pure_;
 int string_compare_func(const void *a, const void *b) _pure_;
+extern const struct hash_ops string_hash_ops;
 
 /* This will compare the passed pointers directly, and will not
  * dereference them. This is hence not useful for strings or
  * suchlike. */
 unsigned long trivial_hash_func(const void *p, const uint8_t hash_key[HASH_KEY_SIZE]) _pure_;
 int trivial_compare_func(const void *a, const void *b) _const_;
+extern const struct hash_ops trivial_hash_ops;
 
 /* 32bit values we can always just embedd in the pointer itself, but
  * in order to support 32bit archs we need store 64bit values
  * indirectly, since they don't fit in a pointer. */
 unsigned long uint64_hash_func(const void *p, const uint8_t hash_key[HASH_KEY_SIZE]) _pure_;
 int uint64_compare_func(const void *a, const void *b) _pure_;
+extern const struct hash_ops uint64_hash_ops;
 
 /* On some archs dev_t is 32bit, and on others 64bit. And sometimes
  * it's 64bit on 32bit archs, and sometimes 32bit on 64bit archs. Yuck! */
 #if SIZEOF_DEV_T != 8
 unsigned long devt_hash_func(const void *p, const uint8_t hash_key[HASH_KEY_SIZE]) _pure_;
 int devt_compare_func(const void *a, const void *b) _pure_;
+extern const struct hash_ops devt_hash_ops = {
+        .hash = devt_hash_func,
+        .compare = devt_compare_func
+};
 #else
-/* No need to define a second version of this... */
 #define devt_hash_func uint64_hash_func
 #define devt_compare_func uint64_compare_func
+#define devt_hash_ops uint64_hash_ops
 #endif
 
-Hashmap *hashmap_new(hash_func_t hash_func, compare_func_t compare_func);
+Hashmap *hashmap_new(const struct hash_ops *hash_ops);
 void hashmap_free(Hashmap *h);
 void hashmap_free_free(Hashmap *h);
 void hashmap_free_free_free(Hashmap *h);
 Hashmap *hashmap_copy(Hashmap *h);
-int hashmap_ensure_allocated(Hashmap **h, hash_func_t hash_func, compare_func_t compare_func);
+int hashmap_ensure_allocated(Hashmap **h, const struct hash_ops *hash_ops);
 
 int hashmap_put(Hashmap *h, const void *key, void *value);
 int hashmap_update(Hashmap *h, const void *key, void *value);