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.

2 files changed, 3 insertions, 6 deletions

diff --git a/src/shared/dns-domain.c b/src/shared/dns-domain.c
index 6dc04d51e4..1517443736 100644
--- a/src/shared/dns-domain.c
+++ b/src/shared/dns-domain.c
@@ -379,9 +379,8 @@ int dns_name_concat(const char *a, const char *b, char **_ret) {
         return 0;
 }
 
-unsigned long dns_name_hash_func(const void *s, const uint8_t hash_key[HASH_KEY_SIZE]) {
+void dns_name_hash_func(const void *s, struct siphash *state) {
         const char *p = s;
-        unsigned long ul = hash_key[0];
         int r;
 
         assert(p);
@@ -403,10 +402,8 @@ unsigned long dns_name_hash_func(const void *s, const uint8_t hash_key[HASH_KEY_
                 label[r] = 0;
                 ascii_strlower(label);
 
-                ul = ul * hash_key[1] + ul + string_hash_func(label, hash_key);
+                string_hash_func(label, state);
         }
-
-        return ul;
 }
 
 int dns_name_compare_func(const void *a, const void *b) {
diff --git a/src/shared/dns-domain.h b/src/shared/dns-domain.h
index 8e73d9c20f..1f0d242c18 100644
--- a/src/shared/dns-domain.h
+++ b/src/shared/dns-domain.h
@@ -54,7 +54,7 @@ static inline int dns_name_is_valid(const char *s) {
         return 1;
 }
 
-unsigned long dns_name_hash_func(const void *s, const uint8_t hash_key[HASH_KEY_SIZE]);
+void dns_name_hash_func(const void *s, struct siphash *state);
 int dns_name_compare_func(const void *a, const void *b);
 extern const struct hash_ops dns_name_hash_ops;