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/resolve/resolved-dns-cache.c

@@ -186,7 +186,7 @@ static int dns_cache_init(DnsCache *c) {
         if (r < 0)
                 return r;
 
-        r = hashmap_ensure_allocated(&c->by_key, dns_resource_key_hash_func, dns_resource_key_compare_func);
+        r = hashmap_ensure_allocated(&c->by_key, &dns_resource_key_hash_ops);
         if (r < 0)
                 return r;
 

src/resolve/resolved-dns-domain.c

@@ -371,6 +371,11 @@ int dns_name_compare_func(const void *a, const void *b) {
         }
 }
 
+const struct hash_ops dns_name_hash_ops = {
+        .hash = dns_name_hash_func,
+        .compare = dns_name_compare_func
+};
+
 int dns_name_equal(const char *x, const char *y) {
         int r, q, k, w;
 

src/resolve/resolved-dns-domain.h

@@ -37,6 +37,7 @@ int dns_name_normalize(const char *s, char **_ret);
 
 unsigned long dns_name_hash_func(const void *s, const uint8_t hash_key[HASH_KEY_SIZE]);
 int dns_name_compare_func(const void *a, const void *b);
+extern const struct hash_ops dns_name_hash_ops;
 
 int dns_name_equal(const char *x, const char *y);
 int dns_name_endswith(const char *name, const char *suffix);

src/resolve/resolved-dns-packet.c

@@ -433,9 +433,7 @@ int dns_packet_append_name(DnsPacket *p, const char *name,
                         goto fail;
 
                 if (allow_compression) {
-                        r = hashmap_ensure_allocated(&p->names,
-                                                     dns_name_hash_func,
-                                                     dns_name_compare_func);
+                        r = hashmap_ensure_allocated(&p->names, &dns_name_hash_ops);
                         if (r < 0)
                                 goto fail;
 

src/resolve/resolved-dns-query.c

@@ -144,7 +144,7 @@ static int dns_query_add_transaction(DnsQuery *q, DnsScope *s, DnsResourceKey *k
         assert(q);
         assert(s);
 
-        r = set_ensure_allocated(&q->transactions, NULL, NULL);
+        r = set_ensure_allocated(&q->transactions, NULL);
         if (r < 0)
                 return r;
 
@@ -166,7 +166,7 @@ static int dns_query_add_transaction(DnsQuery *q, DnsScope *s, DnsResourceKey *k
                         return r;
         }
 
-        r = set_ensure_allocated(&t->queries, NULL, NULL);
+        r = set_ensure_allocated(&t->queries, NULL);
         if (r < 0)
                 goto gc;
 

src/resolve/resolved-dns-rr.c

@@ -133,7 +133,7 @@ int dns_resource_key_match_cname(const DnsResourceKey *key, const DnsResourceRec
         return dns_name_equal(DNS_RESOURCE_KEY_NAME(rr->key), DNS_RESOURCE_KEY_NAME(key));
 }
 
-unsigned long dns_resource_key_hash_func(const void *i, const uint8_t hash_key[HASH_KEY_SIZE]) {
+static unsigned long dns_resource_key_hash_func(const void *i, const uint8_t hash_key[HASH_KEY_SIZE]) {
         const DnsResourceKey *k = i;
         unsigned long ul;
 
@@ -144,7 +144,7 @@ unsigned long dns_resource_key_hash_func(const void *i, const uint8_t hash_key[H
         return ul;
 }
 
-int dns_resource_key_compare_func(const void *a, const void *b) {
+static int dns_resource_key_compare_func(const void *a, const void *b) {
         const DnsResourceKey *x = a, *y = b;
         int ret;
 
@@ -165,6 +165,11 @@ int dns_resource_key_compare_func(const void *a, const void *b) {
         return 0;
 }
 
+const struct hash_ops dns_resource_key_hash_ops = {
+        .hash = dns_resource_key_hash_func,
+        .compare = dns_resource_key_compare_func
+};
+
 int dns_resource_key_to_string(const DnsResourceKey *key, char **ret) {
         char cbuf[DECIMAL_STR_MAX(uint16_t)], tbuf[DECIMAL_STR_MAX(uint16_t)];
         const char *c, *t;

src/resolve/resolved-dns-rr.h

@@ -159,8 +159,6 @@ DnsResourceKey* dns_resource_key_unref(DnsResourceKey *key);
 int dns_resource_key_equal(const DnsResourceKey *a, const DnsResourceKey *b);
 int dns_resource_key_match_rr(const DnsResourceKey *key, const DnsResourceRecord *rr);
 int dns_resource_key_match_cname(const DnsResourceKey *key, const DnsResourceRecord *rr);
-unsigned long dns_resource_key_hash_func(const void *i, const uint8_t hash_key[HASH_KEY_SIZE]);
-int dns_resource_key_compare_func(const void *a, const void *b);
 int dns_resource_key_to_string(const DnsResourceKey *key, char **ret);
 DEFINE_TRIVIAL_CLEANUP_FUNC(DnsResourceKey*, dns_resource_key_unref);
 
@@ -175,3 +173,5 @@ DEFINE_TRIVIAL_CLEANUP_FUNC(DnsResourceRecord*, dns_resource_record_unref);
 
 const char *dns_class_to_string(uint16_t type);
 int dns_class_from_string(const char *name, uint16_t *class);
+
+extern const struct hash_ops dns_resource_key_hash_ops;

src/resolve/resolved-dns-scope.c

@@ -709,7 +709,7 @@ int dns_scope_notify_conflict(DnsScope *scope, DnsResourceRecord *rr) {
 
         /* We don't send these queries immediately. Instead, we queue
          * them, and send them after some jitter delay. */
-        r = hashmap_ensure_allocated(&scope->conflict_queue, dns_resource_key_hash_func, dns_resource_key_compare_func);
+        r = hashmap_ensure_allocated(&scope->conflict_queue, &dns_resource_key_hash_ops);
         if (r < 0) {
                 log_oom();
                 return r;

src/resolve/resolved-dns-server.c

@@ -100,7 +100,7 @@ DnsServer* dns_server_free(DnsServer *s)  {
         return NULL;
 }
 
-unsigned long dns_server_hash_func(const void *p, const uint8_t hash_key[HASH_KEY_SIZE]) {
+static unsigned long dns_server_hash_func(const void *p, const uint8_t hash_key[HASH_KEY_SIZE]) {
         const DnsServer *s = p;
         uint64_t u;
 
@@ -110,7 +110,7 @@ unsigned long dns_server_hash_func(const void *p, const uint8_t hash_key[HASH_KE
         return u;
 }
 
-int dns_server_compare_func(const void *a, const void *b) {
+static int dns_server_compare_func(const void *a, const void *b) {
         const DnsServer *x = a, *y = b;
 
         if (x->family < y->family)
@@ -120,3 +120,8 @@ int dns_server_compare_func(const void *a, const void *b) {
 
         return memcmp(&x->address, &y->address, FAMILY_ADDRESS_SIZE(x->family));
 }
+
+const struct hash_ops dns_server_hash_ops = {
+        .hash = dns_server_hash_func,
+        .compare = dns_server_compare_func
+};

src/resolve/resolved-dns-server.h

@@ -60,5 +60,4 @@ int dns_server_new(
 
 DnsServer* dns_server_free(DnsServer *s);
 
-unsigned long dns_server_hash_func(const void *p, const uint8_t hash_key[HASH_KEY_SIZE]);
-int dns_server_compare_func(const void *a, const void *b);
+extern const struct hash_ops dns_server_hash_ops;

src/resolve/resolved-dns-transaction.c

@@ -78,7 +78,7 @@ int dns_transaction_new(DnsTransaction **ret, DnsScope *s, DnsQuestion *q) {
         assert(s);
         assert(q);
 
-        r = hashmap_ensure_allocated(&s->manager->dns_transactions, NULL, NULL);
+        r = hashmap_ensure_allocated(&s->manager->dns_transactions, NULL);
         if (r < 0)
                 return r;
 

src/resolve/resolved-dns-zone.c

@@ -126,11 +126,11 @@ static int dns_zone_init(DnsZone *z) {
 
         assert(z);
 
-        r = hashmap_ensure_allocated(&z->by_key, dns_resource_key_hash_func, dns_resource_key_compare_func);
+        r = hashmap_ensure_allocated(&z->by_key, &dns_resource_key_hash_ops);
         if (r < 0)
                 return r;
 
-        r = hashmap_ensure_allocated(&z->by_name, dns_name_hash_func, dns_name_compare_func);
+        r = hashmap_ensure_allocated(&z->by_name, &dns_name_hash_ops);
         if (r < 0)
                 return r;
 
@@ -194,7 +194,7 @@ static int dns_zone_item_probe_start(DnsZoneItem *i)  {
                         return r;
         }
 
-        r = set_ensure_allocated(&t->zone_items, NULL, NULL);
+        r = set_ensure_allocated(&t->zone_items, NULL);
         if (r < 0)
                 goto gc;
 

src/resolve/resolved-link.c

@@ -33,7 +33,7 @@ int link_new(Manager *m, Link **ret, int ifindex) {
         assert(m);
         assert(ifindex > 0);
 
-        r = hashmap_ensure_allocated(&m->links, NULL, NULL);
+        r = hashmap_ensure_allocated(&m->links, NULL);
         if (r < 0)
                 return r;
 

src/resolve/resolved-manager.c

@@ -737,11 +737,11 @@ int manager_write_resolv_conf(Manager *m) {
         manager_read_resolv_conf(m);
 
         /* Add the full list to a set, to filter out duplicates */
-        dns = set_new(dns_server_hash_func, dns_server_compare_func);
+        dns = set_new(&dns_server_hash_ops);
         if (!dns)
                 return -ENOMEM;
 
-        domains = set_new(dns_name_hash_func, dns_name_compare_func);
+        domains = set_new(&dns_name_hash_ops);
         if (!domains)
                 return -ENOMEM;