siphash24: change result argument to uint64_t

Change the "out" parameter from uint8_t[8] to uint64_t. On architectures which
enforce pointer alignment this fixes crashes when we previously cast an
unaligned array to uint64_t*, and on others this should at least improve
performance as the compiler now aligns these properly.

This also simplifies the code in most cases by getting rid of typecasts. The
only place which we can't change is struct duid's en.id, as that is _packed_
and public API, so we can't enforce alignment of the "id" field and have to
use memcpy instead.

src/basic/hashmap.c

@@ -380,7 +380,7 @@ static unsigned base_bucket_hash(HashmapBase *h, const void *p) {
 
         h->hash_ops->hash(p, &state);
 
-        siphash24_finalize((uint8_t*)&hash, &state);
+        siphash24_finalize(&hash, &state);
 
         return (unsigned) (hash % n_buckets(h));
 }

src/basic/siphash24.c

@@ -141,7 +141,7 @@ void siphash24_compress(const void *_in, size_t inlen, struct siphash *state) {
         }
 }
 
-void siphash24_finalize(uint8_t out[8], struct siphash *state) {
+void siphash24_finalize(uint64_t *out, struct siphash *state) {
         uint64_t b;
 
         b = state->padding | (( ( uint64_t )state->inlen ) << 56);
@@ -174,7 +174,7 @@ void siphash24_finalize(uint8_t out[8], struct siphash *state) {
 }
 
 /* SipHash-2-4 */
-void siphash24(uint8_t out[8], const void *_in, size_t inlen, const uint8_t k[16]) {
+void siphash24(uint64_t *out, const void *_in, size_t inlen, const uint8_t k[16]) {
         struct siphash state;
 
         siphash24_init(&state, k);

src/basic/siphash24.h

@@ -14,6 +14,6 @@ struct siphash {
 
 void siphash24_init(struct siphash *state, const uint8_t k[16]);
 void siphash24_compress(const void *in, size_t inlen, struct siphash *state);
-void siphash24_finalize(uint8_t out[8], struct siphash *state);
+void siphash24_finalize(uint64_t *out, struct siphash *state);
 
-void siphash24(uint8_t out[8], const void *in, size_t inlen, const uint8_t k[16]);
+void siphash24(uint64_t *out, const void *in, size_t inlen, const uint8_t k[16]);