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author | Martin Mares <mj@ucw.cz> | 1998-12-20 14:57:49 +0100 |
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committer | Martin Mares <mj@ucw.cz> | 1998-12-20 14:57:49 +0100 |
commit | a6f250f5c6d079badc4a1274b19a21a52de6acec (patch) | |
tree | 0a8fde53fead5ee11b88af0156ba2555f7cc6d3e | |
parent | a05406e69c699c8b6f43bf58f47b8b0385113083 (diff) | |
download | bird-a6f250f5c6d079badc4a1274b19a21a52de6acec.tar bird-a6f250f5c6d079badc4a1274b19a21a52de6acec.zip |
New hash functions according to benchmarks posted yesterday. (The IPv6
version has not been benchmarked yet due to insufficient test data.)
Now ipa_hash() returns a uniformely distributed 16-bit value.
-rw-r--r-- | lib/ipv4.h | 6 | ||||
-rw-r--r-- | lib/ipv6.h | 2 |
2 files changed, 5 insertions, 3 deletions
@@ -61,10 +61,12 @@ typedef u32 ip_addr; int ipv4_classify(u32); u32 ipv4_class_mask(u32); -/* FIXME: Is this hash function uniformly distributed over standard routing tables? */ static inline unsigned ipv4_hash(u32 a) { - return a ^ (a >> 16) ^ (a >> 24); + /* Returns a 16-bit value */ + a ^= a >> 16; + a ^= a << 10; + return a & 0xffff; } #endif @@ -59,7 +59,7 @@ void ipv6_ntoh(ip_addr *); static inline unsigned ipv6_hash(ip_addr *a) { u32 x = _I0(*a) ^ _I1(*a) ^ _I2(*a) ^ _I3(*a); - return x ^ (x >> 16) ^ (x >> 8); + return (x ^ (x >> 16) ^ (x >> 8)) & 0xffff; } #endif |