diff options
author | Stephen Hemminger <shemminger@vyatta.com> | 2010-08-27 14:11:14 -0700 |
---|---|---|
committer | Paul Jakma <paul@quagga.net> | 2011-03-21 13:30:54 +0000 |
commit | 6392aa83c4f895ebbd23817c68d9b0da0de2e0f8 (patch) | |
tree | 535c89a194ec7fd3b9f4a6e33ceab10579e62329 /lib | |
parent | 25ff1e88bb5f1b0a16a364d7206db3ebdc5ecf52 (diff) |
lib: Better hashing of string values using Bernstein hash
* hash.{h,c}: (string_hash_make) Hash optimised for strings, current
implementation using Bernstein hash, which offers a good compromise
between distribution and performance.
* distribute.c: (distribute_hash_make) use previous instead of additive
string hash.
* if_rmap.c: (if_rmap_hash_make) ditto
Diffstat (limited to 'lib')
-rw-r--r-- | lib/distribute.c | 13 | ||||
-rw-r--r-- | lib/hash.c | 11 | ||||
-rw-r--r-- | lib/hash.h | 2 | ||||
-rw-r--r-- | lib/if_rmap.c | 9 |
4 files changed, 19 insertions, 16 deletions
diff --git a/lib/distribute.c b/lib/distribute.c index 242a225c..420849da 100644 --- a/lib/distribute.c +++ b/lib/distribute.c @@ -114,16 +114,11 @@ distribute_get (const char *ifname) } static unsigned int -distribute_hash_make (struct distribute *dist) +distribute_hash_make (void *arg) { - unsigned int i, key; + const struct distribute *dist = arg; - key = 0; - if (dist->ifname) - for (i = 0; i < strlen (dist->ifname); i++) - key += dist->ifname[i]; - - return key; + return dist->ifname ? string_hash_make (dist->ifname) : 0; } /* If two distribute-list have same value then return 1 else return @@ -763,7 +758,7 @@ distribute_list_reset () void distribute_list_init (int node) { - disthash = hash_create ((unsigned int (*) (void *)) distribute_hash_make, + disthash = hash_create (distribute_hash_make, (int (*) (const void *, const void *)) distribute_cmp); if(node==RIP_NODE) { @@ -101,6 +101,17 @@ hash_lookup (struct hash *hash, void *data) return hash_get (hash, data, NULL); } +/* Simple Bernstein hash which is simple and fast for common case */ +unsigned int string_hash_make (const char *str) +{ + unsigned int hash = 0; + + while (*str) + hash = (hash * 33) ^ (unsigned int) *str++; + + return hash; +} + /* This function release registered value from specified hash. When release is successfully finished, return the data pointer in the hash backet. */ @@ -70,4 +70,6 @@ extern void hash_iterate (struct hash *, extern void hash_clean (struct hash *, void (*) (void *)); extern void hash_free (struct hash *); +extern unsigned int string_hash_make (const char *); + #endif /* _ZEBRA_HASH_H */ diff --git a/lib/if_rmap.c b/lib/if_rmap.c index ddc62fd5..9774be4b 100644 --- a/lib/if_rmap.c +++ b/lib/if_rmap.c @@ -109,14 +109,9 @@ if_rmap_get (const char *ifname) static unsigned int if_rmap_hash_make (void *data) { - struct if_rmap *if_rmap = data; - unsigned int i, key; + const struct if_rmap *if_rmap = data; - key = 0; - for (i = 0; i < strlen (if_rmap->ifname); i++) - key += if_rmap->ifname[i]; - - return key; + return string_hash_make (if_rmap->ifname); } static int |