Add a complete implementation of MurmurHash3. Tweak both implementations
so they match the established idiom. Document them in hash(9). MFC after: 1 month MFC with: r272906
This commit is contained in:
Dag-Erling Smørgrav
parent
78701de4b7
commit
99e9de871a
@ -26,7 +26,7 @@
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.\" $OpenBSD: hash.9,v 1.5 2003/04/17 05:08:39 jmc Exp $
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.\" $FreeBSD$
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.\"
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.Dd September 4, 2012
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.Dd October 18, 2014
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.Dt HASH 9
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.Os
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.Sh NAME
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@ -37,8 +37,10 @@
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.Nm hash32_strn ,
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.Nm hash32_stre ,
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.Nm hash32_strne ,
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.Nm jenkins_hash ,
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.Nm jenkins_hash32 ,
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.Nm jenkins_hash
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.Nm murmur3_32_hash ,
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.Nm murmur3_32_hash32
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.Nd general kernel hashing functions
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.Sh SYNOPSIS
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.In sys/hash.h
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@ -56,6 +58,10 @@
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.Fn jenkins_hash "const void *buf" "size_t len" "uint32_t hash"
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.Ft uint32_t
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.Fn jenkins_hash32 "const uint32_t *buf" "size_t count" "uint32_t hash"
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.Ft uint32_t
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.Fn murmur3_32_hash "const void *buf" "size_t len" "uint32_t hash"
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.Ft uint32_t
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.Fn murmur3_32_hash32 "const uint32_t *buf" "size_t count" "uint32_t hash"
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.Sh DESCRIPTION
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The
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.Fn hash32
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@ -130,6 +136,16 @@ sized arrays, thus is simplier and faster.
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It accepts an array of
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.Ft uint32_t
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values in its first argument and size of this array in the second argument.
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.Pp
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The
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.Fn murmur3_32_hash
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and
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.Fn murmur3_32_hash32
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functions are similar to
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.Fn jenkins_hash
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and
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.Fn jenkins_hash32 ,
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but implement the 32-bit version of MurmurHash3.
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.Sh RETURN VALUES
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The
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.Fn hash32
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@ -185,6 +201,10 @@ The
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.Nm jenkins_hash
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functions were added in
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.Fx 10.0 .
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The
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.Nm murmur3_32_hash
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functions were added in
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.Fx 10.1 .
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.Sh AUTHORS
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The
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.Nm hash32
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@ -192,5 +212,9 @@ functions were written by
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.An Tobias Weingartner .
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The
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.Nm jenkins_hash
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functions was written by
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Bob Jenkins .
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functions were written by
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.An Bob Jenkins .
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The
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.Nm murmur3_32_hash
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functions were written by
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.An Dag-Erling Sm\(/orgrav Aq Mt des@FreeBSD.org .
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@ -22,6 +22,8 @@
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* LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
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* OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
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* SUCH DAMAGE.
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*
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* $FreeBSD$
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*/
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#include <sys/hash.h>
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@ -32,27 +34,31 @@
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#define rol32(i32, n) ((i32) << (n) | (i32) >> (32 - (n)))
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/*
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* $FreeBSD$
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* Simple implementation of the Murmur3-32 hash function optimized for
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* aligned sequences of 32-bit words. If len is not a multiple of 4, it
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* will be rounded down, droping trailer bytes.
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* Simple implementation of the Murmur3-32 hash function.
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*
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* This implementation is slow but safe. It can be made significantly
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* faster if the caller guarantees that the input is correctly aligned for
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* 32-bit reads, and slightly faster yet if the caller guarantees that the
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* length of the input is always a multiple of 4 bytes.
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*/
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uint32_t
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murmur3_aligned_32(const void *data, size_t len, uint32_t seed)
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murmur3_32_hash(const void *data, size_t len, uint32_t seed)
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{
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const uint32_t *data32;
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const uint8_t *bytes;
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uint32_t hash, k;
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size_t res;
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/* initialize */
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len -= len % sizeof(*data32);
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/* initialization */
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bytes = data;
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res = len;
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data32 = data;
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hash = seed;
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/* iterate */
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for (res = 0; res < len; res += sizeof(*data32), data32++) {
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k = le32toh(*data32);
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/* main loop */
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while (res >= 4) {
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/* replace with le32toh() if input is aligned */
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k = le32dec(bytes);
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bytes += 4;
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res -= 4;
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k *= 0xcc9e2d51;
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k = rol32(k, 15);
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k *= 0x1b873593;
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@ -62,6 +68,25 @@ murmur3_aligned_32(const void *data, size_t len, uint32_t seed)
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hash += 0xe6546b64;
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}
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/* remainder */
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/* remove if input length is a multiple of 4 */
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if (res > 0) {
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k = 0;
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switch (res) {
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case 3:
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k |= bytes[2] << 16;
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case 2:
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k |= bytes[1] << 8;
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case 1:
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k |= bytes[0];
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k *= 0xcc9e2d51;
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k = rol32(k, 15);
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k *= 0x1b873593;
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hash ^= k;
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break;
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}
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}
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/* finalize */
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hash ^= (uint32_t)len;
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hash ^= hash >> 16;
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@ -72,3 +97,36 @@ murmur3_aligned_32(const void *data, size_t len, uint32_t seed)
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return (hash);
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}
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/*
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* Simplified version of the above optimized for aligned sequences of
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* 32-bit words. The count argument is the number of words, not the
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* length in bytes.
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*/
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uint32_t
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murmur3_32_hash32(const uint32_t *data, size_t count, uint32_t seed)
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{
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uint32_t hash, k;
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size_t res;
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/* iterate */
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for (res = count, hash = seed; res > 0; res--, data++) {
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k = le32toh(*data);
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k *= 0xcc9e2d51;
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k = rol32(k, 15);
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k *= 0x1b873593;
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hash ^= k;
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hash = rol32(hash, 13);
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hash *= 5;
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hash += 0xe6546b64;
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}
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/* finalize */
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hash ^= (uint32_t)count;
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hash ^= hash >> 16;
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hash *= 0x85ebca6b;
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hash ^= hash >> 13;
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hash *= 0xc2b2ae35;
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hash ^= hash >> 16;
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return (hash);
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}
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@ -374,9 +374,9 @@ pf_hashkey(struct pf_state_key *sk)
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{
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uint32_t h;
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h = murmur3_aligned_32((uint32_t *)sk,
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sizeof(struct pf_state_key_cmp),
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V_pf_hashseed);
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h = murmur3_32_hash32((uint32_t *)sk,
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sizeof(struct pf_state_key_cmp)/sizeof(uint32_t),
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V_pf_hashseed);
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return (h & pf_hashmask);
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}
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@ -388,12 +388,12 @@ pf_hashsrc(struct pf_addr *addr, sa_family_t af)
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switch (af) {
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case AF_INET:
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h = murmur3_aligned_32((uint32_t *)&addr->v4,
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sizeof(addr->v4), V_pf_hashseed);
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h = murmur3_32_hash32((uint32_t *)&addr->v4,
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sizeof(addr->v4)/sizeof(uint32_t), V_pf_hashseed);
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break;
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case AF_INET6:
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h = murmur3_aligned_32((uint32_t *)&addr->v6,
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sizeof(addr->v6), V_pf_hashseed);
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h = murmur3_32_hash32((uint32_t *)&addr->v6,
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sizeof(addr->v6)/sizeof(uint32_t), V_pf_hashseed);
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break;
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default:
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panic("%s: unknown address family %u", __func__, af);
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@ -126,7 +126,8 @@ hash32_strne(const void *buf, size_t len, int end, const char **ep,
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uint32_t jenkins_hash(const void *, size_t, uint32_t);
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uint32_t jenkins_hash32(const uint32_t *, size_t, uint32_t);
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uint32_t murmur3_aligned_32(const void *data, size_t len, uint32_t seed);
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uint32_t murmur3_32_hash(const void *, size_t, uint32_t);
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uint32_t murmur3_32_hash32(const uint32_t *, size_t, uint32_t);
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#endif /* _KERNEL */
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