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+/* Copyright (C) 2011 CZ.NIC, z.s.p.o. <knot-dns@labs.nic.cz>
+
+ This program is free software: you can redistribute it and/or modify
+ it under the terms of the GNU General Public License as published by
+ the Free Software Foundation, either version 3 of the License, or
+ (at your option) any later version.
+
+ This program is distributed in the hope that it will be useful,
+ but WITHOUT ANY WARRANTY; without even the implied warranty of
+ MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+ GNU General Public License for more details.
+
+ You should have received a copy of the GNU General Public License
+ along with this program. If not, see <http://www.gnu.org/licenses/>.
+ */
+
+#include <config.h>
+#include "hash-functions.h"
+
+/*--------------------------------- FNV HASH ---------------------------------*/
+
+unsigned long int fnv_hash(const char *data, int size, int bits)
+{
+ int shift, i;
+ unsigned long int mask;
+ unsigned long int hash = 2166136261;
+
+ if (bits == -1) {
+ shift = 0;
+ mask = 0xFFFFFFFF;
+ } else {
+ shift = 32 - bits;
+ mask = (1U << shift) - 1U;
+ }
+
+ for (i = 0; i < size; i++) {
+ hash = (hash * 16777619) ^ data[i];
+ }
+
+ if (shift == 0) {
+ return hash;
+ }
+
+ return (hash ^(hash >> shift)) & mask;
+}
+
+/*------------------------------- JENKINS HASH -------------------------------*/
+
+/* The mixing step */
+/*
+#define mix(a,b,c) \
+ { \
+ a=a-b; a=a-c; a=a^(c>>13); \
+ b=b-c; b=b-a; b=b^(a<<8); \
+ c=c-a; c=c-b; c=c^(b>>13); \
+ a=a-b; a=a-c; a=a^(c>>12); \
+ b=b-c; b=b-a; b=b^(a<<16); \
+ c=c-a; c=c-b; c=c^(b>>5); \
+ a=a-b; a=a-c; a=a^(c>>3); \
+ b=b-c; b=b-a; b=b^(a<<10); \
+ c=c-a; c=c-b; c=c^(b>>15); \
+ }
+*/
+
+///* The whole new hash function */
+//u4 jhash(register u1 *k, u4 length, u4 initval)
+//{
+// register u4 a, b, c; /* the internal state */
+// u4 len; /* how many key bytes still need mixing */
+
+// /* Set up the internal state */
+// len = length;
+// a = b = 0x9e3779b9; /* the golden ratio; an arbitrary value */
+// c = initval; /* variable initialization of internal state */
+
+// /*---------------------------------------- handle most of the key */
+// while (len >= 12) {
+// a = a + (k[0] + ((u4)k[1] << 8)
+// + ((u4)k[2] << 16) + ((u4)k[3] << 24));
+// b = b + (k[4] + ((u4)k[5] << 8)
+// + ((u4)k[6] << 16) + ((u4)k[7] << 24));
+// c = c + (k[8] + ((u4)k[9] << 8)
+// + ((u4)k[10] << 16) + ((u4)k[11] << 24));
+// mix(a, b, c);
+// k = k + 12;
+// len = len - 12;
+// }
+
+// /*------------------------------------- handle the last 11 bytes */
+// c = c + length;
+// switch (len) { /* all the case statements fall through */
+// case 11:
+// c = c + ((u4)k[10] << 24);
+// case 10:
+// c = c + ((u4)k[9] << 16);
+// case 9 :
+// c = c + ((u4)k[8] << 8);
+// /* the first byte of c is reserved for the length */
+// case 8 :
+// b = b + ((u4)k[7] << 24);
+// case 7 :
+// b = b + ((u4)k[6] << 16);
+// case 6 :
+// b = b + ((u4)k[5] << 8);
+// case 5 :
+// b = b + k[4];
+// case 4 :
+// a = a + ((u4)k[3] << 24);
+// case 3 :
+// a = a + ((u4)k[2] << 16);
+// case 2 :
+// a = a + ((u4)k[1] << 8);
+// case 1 :
+// a = a + k[0];
+// /* case 0: nothing left to add */
+// }
+// mix(a, b, c);
+// /*-------------------------------------------- report the result */
+// return c;
+//}
+
+
+
+#define hashsize(n) ((ub4)1<<(n))
+#define hashmask(n) (hashsize(n)-1)
+
+/*
+--------------------------------------------------------------------
+mix -- mix 3 32-bit values reversibly.
+For every delta with one or two bits set, and the deltas of all three
+ high bits or all three low bits, whether the original value of a,b,c
+ is almost all zero or is uniformly distributed,
+* If mix() is run forward or backward, at least 32 bits in a,b,c
+ have at least 1/4 probability of changing.
+* If mix() is run forward, every bit of c will change between 1/3 and
+ 2/3 of the time. (Well, 22/100 and 78/100 for some 2-bit deltas.)
+mix() was built out of 36 single-cycle latency instructions in a
+ structure that could supported 2x parallelism, like so:
+ a -= b;
+ a -= c; x = (c>>13);
+ b -= c; a ^= x;
+ b -= a; x = (a<<8);
+ c -= a; b ^= x;
+ c -= b; x = (b>>13);
+ ...
+ Unfortunately, superscalar Pentiums and Sparcs can't take advantage
+ of that parallelism. They've also turned some of those single-cycle
+ latency instructions into multi-cycle latency instructions. Still,
+ this is the fastest good hash I could find. There were about 2^^68
+ to choose from. I only looked at a billion or so.
+--------------------------------------------------------------------
+*/
+#define mix(a,b,c) \
+{ \
+ a -= b; a -= c; a ^= (c>>13); \
+ b -= c; b -= a; b ^= (a<<8); \
+ c -= a; c -= b; c ^= (b>>13); \
+ a -= b; a -= c; a ^= (c>>12); \
+ b -= c; b -= a; b ^= (a<<16); \
+ c -= a; c -= b; c ^= (b>>5); \
+ a -= b; a -= c; a ^= (c>>3); \
+ b -= c; b -= a; b ^= (a<<10); \
+ c -= a; c -= b; c ^= (b>>15); \
+}
+
+/*
+--------------------------------------------------------------------
+hash() -- hash a variable-length key into a 32-bit value
+ k : the key (the unaligned variable-length array of bytes)
+ len : the length of the key, counting by bytes
+ initval : can be any 4-byte value
+Returns a 32-bit value. Every bit of the key affects every bit of
+the return value. Every 1-bit and 2-bit delta achieves avalanche.
+About 6*len+35 instructions.
+
+The best hash table sizes are powers of 2. There is no need to do
+mod a prime (mod is sooo slow!). If you need less than 32 bits,
+use a bitmask. For example, if you need only 10 bits, do
+ h = (h & hashmask(10));
+In which case, the hash table should have hashsize(10) elements.
+
+If you are hashing n strings (ub1 **)k, do it like this:
+ for (i=0, h=0; i<n; ++i) h = hash( k[i], len[i], h);
+
+By Bob Jenkins, 1996. bob_jenkins@burtleburtle.net. You may use this
+code any way you wish, private, educational, or commercial. It's free.
+
+See http://burtleburtle.net/bob/hash/evahash.html
+Use for hash table lookup, or anything where one collision in 2^^32 is
+acceptable. Do NOT use for cryptographic purposes.
+--------------------------------------------------------------------
+*/
+
+ub4 jhash(k, length, initval)
+register ub1 *k; /* the key */
+register ub4 length; /* the length of the key */
+register ub4 initval; /* the previous hash, or an arbitrary value */
+{
+ register ub4 a,b,c,len;
+
+ /* Set up the internal state */
+ len = length;
+ a = b = 0x9e3779b9; /* the golden ratio; an arbitrary value */
+ c = initval; /* the previous hash value */
+
+ /*---------------------------------------- handle most of the key */
+ while (len >= 12)
+ {
+ a += (k[0] +((ub4)k[1]<<8) +((ub4)k[2]<<16) +((ub4)k[3]<<24));
+ b += (k[4] +((ub4)k[5]<<8) +((ub4)k[6]<<16) +((ub4)k[7]<<24));
+ c += (k[8] +((ub4)k[9]<<8) +((ub4)k[10]<<16)+((ub4)k[11]<<24));
+ mix(a,b,c);
+ k += 12; len -= 12;
+ }
+
+ /*------------------------------------- handle the last 11 bytes */
+ c += length;
+ switch(len) /* all the case statements fall through */
+ {
+ case 11: c+=((ub4)k[10]<<24);
+ case 10: c+=((ub4)k[9]<<16);
+ case 9 : c+=((ub4)k[8]<<8);
+ /* the first byte of c is reserved for the length */
+ case 8 : b+=((ub4)k[7]<<24);
+ case 7 : b+=((ub4)k[6]<<16);
+ case 6 : b+=((ub4)k[5]<<8);
+ case 5 : b+=k[4];
+ case 4 : a+=((ub4)k[3]<<24);
+ case 3 : a+=((ub4)k[2]<<16);
+ case 2 : a+=((ub4)k[1]<<8);
+ case 1 : a+=k[0];
+ /* case 0: nothing left to add */
+ }
+ mix(a,b,c);
+ /*-------------------------------------------- report the result */
+ return c;
+}
+
+#undef hashsize
+#undef hashmask
+
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