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.

src/libsystemd/sd-bus/bus-match.c

@@ -450,13 +450,13 @@ static int bus_match_add_compare_value(
                 where->child = c;
 
                 if (t == BUS_MATCH_MESSAGE_TYPE) {
-                        c->compare.children = hashmap_new(trivial_hash_func, trivial_compare_func);
+                        c->compare.children = hashmap_new(NULL);
                         if (!c->compare.children) {
                                 r = -ENOMEM;
                                 goto fail;
                         }
                 } else if (BUS_MATCH_CAN_HASH(t)) {
-                        c->compare.children = hashmap_new(string_hash_func, string_compare_func);
+                        c->compare.children = hashmap_new(&string_hash_ops);
                         if (!c->compare.children) {
                                 r = -ENOMEM;
                                 goto fail;

src/libsystemd/sd-bus/bus-objects.c

@@ -225,7 +225,7 @@ static int get_child_nodes(
         assert(n);
         assert(_s);
 
-        s = set_new(string_hash_func, string_compare_func);
+        s = set_new(&string_hash_ops);
         if (!s)
                 return -ENOMEM;
 
@@ -1420,7 +1420,7 @@ static struct node *bus_node_allocate(sd_bus *bus, const char *path) {
         if (n)
                 return n;
 
-        r = hashmap_ensure_allocated(&bus->nodes, string_hash_func, string_compare_func);
+        r = hashmap_ensure_allocated(&bus->nodes, &string_hash_ops);
         if (r < 0)
                 return NULL;
 
@@ -1590,6 +1590,11 @@ static int vtable_member_compare_func(const void *a, const void *b) {
         return strcmp(x->member, y->member);
 }
 
+static const struct hash_ops vtable_member_hash_ops = {
+        .hash = vtable_member_hash_func,
+        .compare = vtable_member_compare_func
+};
+
 static int add_object_vtable_internal(
                 sd_bus *bus,
                 sd_bus_slot **slot,
@@ -1618,11 +1623,11 @@ static int add_object_vtable_internal(
                       !streq(interface, "org.freedesktop.DBus.Peer") &&
                       !streq(interface, "org.freedesktop.DBus.ObjectManager"), -EINVAL);
 
-        r = hashmap_ensure_allocated(&bus->vtable_methods, vtable_member_hash_func, vtable_member_compare_func);
+        r = hashmap_ensure_allocated(&bus->vtable_methods, &vtable_member_hash_ops);
         if (r < 0)
                 return r;
 
-        r = hashmap_ensure_allocated(&bus->vtable_properties, vtable_member_hash_func, vtable_member_compare_func);
+        r = hashmap_ensure_allocated(&bus->vtable_properties, &vtable_member_hash_ops);
         if (r < 0)
                 return r;
 

src/libsystemd/sd-bus/bus-track.c

@@ -166,7 +166,7 @@ _public_ int sd_bus_track_add_name(sd_bus_track *track, const char *name) {
         assert_return(track, -EINVAL);
         assert_return(service_name_is_valid(name), -EINVAL);
 
-        r = hashmap_ensure_allocated(&track->names, string_hash_func, string_compare_func);
+        r = hashmap_ensure_allocated(&track->names, &string_hash_ops);
         if (r < 0)
                 return r;
 

src/libsystemd/sd-bus/bus-util.c

@@ -399,7 +399,7 @@ int bus_verify_polkit_async(
         if (!sender)
                 return -EBADMSG;
 
-        r = hashmap_ensure_allocated(registry, trivial_hash_func, trivial_compare_func);
+        r = hashmap_ensure_allocated(registry, NULL);
         if (r < 0)
                 return r;
 

src/libsystemd/sd-bus/busctl.c

@@ -76,7 +76,7 @@ static int list_bus_names(sd_bus *bus, char **argv) {
 
         pager_open_if_enabled();
 
-        names = hashmap_new(string_hash_func, string_compare_func);
+        names = hashmap_new(&string_hash_ops);
         if (!names)
                 return log_oom();
 

src/libsystemd/sd-bus/sd-bus.c

@@ -1756,7 +1756,7 @@ _public_ int sd_bus_call_async(
         if (!BUS_IS_OPEN(bus->state))
                 return -ENOTCONN;
 
-        r = hashmap_ensure_allocated(&bus->reply_callbacks, uint64_hash_func, uint64_compare_func);
+        r = hashmap_ensure_allocated(&bus->reply_callbacks, &uint64_hash_ops);
         if (r < 0)
                 return r;
 

src/libsystemd/sd-event/sd-event.c

@@ -1032,7 +1032,7 @@ _public_ int sd_event_add_child(
         assert_return(e->state != SD_EVENT_FINISHED, -ESTALE);
         assert_return(!event_pid_changed(e), -ECHILD);
 
-        r = hashmap_ensure_allocated(&e->child_sources, trivial_hash_func, trivial_compare_func);
+        r = hashmap_ensure_allocated(&e->child_sources, NULL);
         if (r < 0)
                 return r;
 
@@ -1123,7 +1123,7 @@ _public_ int sd_event_add_post(
         assert_return(e->state != SD_EVENT_FINISHED, -ESTALE);
         assert_return(!event_pid_changed(e), -ECHILD);
 
-        r = set_ensure_allocated(&e->post_sources, trivial_hash_func, trivial_compare_func);
+        r = set_ensure_allocated(&e->post_sources, NULL);
         if (r < 0)
                 return r;
 

src/libsystemd/sd-rtnl/sd-rtnl.c

@@ -557,7 +557,7 @@ int sd_rtnl_call_async(sd_rtnl *nl,
         assert_return(callback, -EINVAL);
         assert_return(!rtnl_pid_changed(nl), -ECHILD);
 
-        r = hashmap_ensure_allocated(&nl->reply_callbacks, uint64_hash_func, uint64_compare_func);
+        r = hashmap_ensure_allocated(&nl->reply_callbacks, &uint64_hash_ops);
         if (r < 0)
                 return r;