hashmap: refactor hash_func

All our hash functions are based on siphash24(), factor out
siphash_init() and siphash24_finalize() and pass the siphash
state to the hash functions rather than the hash key.

This simplifies the hash functions, and in particular makes
composition simpler as calling siphash24_compress() repeatedly
on separate chunks of input has the same effect as first
concatenating the input and then calling siphash23_compress()
on the result.

1 files changed, 6 insertions, 7 deletions

diff --git a/src/libsystemd-network/sd-dhcp-server.c b/src/libsystemd-network/sd-dhcp-server.c
index 1f167485e3..4ea5a29e5c 100644
--- a/src/libsystemd-network/sd-dhcp-server.c
+++ b/src/libsystemd-network/sd-dhcp-server.c
@@ -110,18 +110,14 @@ sd_dhcp_server *sd_dhcp_server_ref(sd_dhcp_server *server) {
         return server;
 }
 
-unsigned long client_id_hash_func(const void *p,
-                                  const uint8_t hash_key[HASH_KEY_SIZE]) {
-        uint64_t u;
+void client_id_hash_func(const void *p, struct siphash *state) {
         const DHCPClientId *id = p;
 
         assert(id);
         assert(id->length);
         assert(id->data);
 
-        siphash24((uint8_t*) &u, id->data, id->length, hash_key);
-
-        return (unsigned long) u;
+        siphash24_compress(id->data, id->length, state);
 }
 
 int client_id_compare_func(const void *_a, const void *_b) {
@@ -743,13 +739,16 @@ int dhcp_server_handle_message(sd_dhcp_server *server, DHCPMessage *message,
                 if (existing_lease)
                         address = existing_lease->address;
                 else {
+                        struct siphash state;
                         uint32_t next_offer;
 
                         /* even with no persistence of leases, we try to offer the same client
                            the same IP address. we do this by using the hash of the client id
                            as the offset into the pool of leases when finding the next free one */
 
-                        next_offer = client_id_hash_func(&req->client_id, HASH_KEY.bytes) % server->pool_size;
+                        siphash_init(&state, HASH_KEY.bytes);
+                        client_id_hash_func(&req->client_id, &state);
+                        next_offer = siphash24_finalize(&state) % server->pool_size;
 
                         for (i = 0; i < server->pool_size; i++) {
                                 if (!server->bound_leases[next_offer]) {