+++ /dev/null
-/*
- * Copyright (C) 2011 Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
- *
- * This library is free software; you can redistribute it and/or
- * modify it under the terms of the GNU Lesser General Public
- * License as published by the Free Software Foundation;
- * version 2.1 of the License.
- *
- * This library 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
- * Lesser General Public License for more details.
- *
- * You should have received a copy of the GNU Lesser General Public
- * License along with this library; if not, write to the Free Software
- * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
- */
-
-#include <urcu/compiler.h>
-#include <endian.h>
-
-/*
- * Hash function
- * Source: http://burtleburtle.net/bob/c/lookup3.c
- * Originally Public Domain
- */
-
-#define rot(x, k) (((x) << (k)) | ((x) >> (32 - (k))))
-
-#define mix(a, b, c) \
-do { \
- a -= c; a ^= rot(c, 4); c += b; \
- b -= a; b ^= rot(a, 6); a += c; \
- c -= b; c ^= rot(b, 8); b += a; \
- a -= c; a ^= rot(c, 16); c += b; \
- b -= a; b ^= rot(a, 19); a += c; \
- c -= b; c ^= rot(b, 4); b += a; \
-} while (0)
-
-#define final(a, b, c) \
-{ \
- c ^= b; c -= rot(b, 14); \
- a ^= c; a -= rot(c, 11); \
- b ^= a; b -= rot(a, 25); \
- c ^= b; c -= rot(b, 16); \
- a ^= c; a -= rot(c, 4);\
- b ^= a; b -= rot(a, 14); \
- c ^= b; c -= rot(b, 24); \
-}
-
-#if (BYTE_ORDER == LITTLE_ENDIAN)
-#define HASH_LITTLE_ENDIAN 1
-#else
-#define HASH_LITTLE_ENDIAN 0
-#endif
-
-/*
- *
- * hashlittle() -- hash a variable-length key into a 32-bit value
- * k : the key (the unaligned variable-length array of bytes)
- * length : 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. Two keys differing by one or two bits will have
- * totally different hash values.
- *
- * 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 (uint8_t **)k, do it like this:
- * for (i = 0, h = 0; i < n; ++i) h = hashlittle(k[i], len[i], h);
- *
- * By Bob Jenkins, 2006. bob_jenkins@burtleburtle.net. You may use this
- * code any way you wish, private, educational, or commercial. It's free.
- *
- * Use for hash table lookup, or anything where one collision in 2^^32 is
- * acceptable. Do NOT use for cryptographic purposes.
- */
-static
-uint32_t hashlittle(const void *key, size_t length, uint32_t initval)
-{
- uint32_t a, b, c; /* internal state */
- union {
- const void *ptr;
- size_t i;
- } u;
-
- /* Set up the internal state */
- a = b = c = 0xdeadbeef + ((uint32_t)length) + initval;
-
- u.ptr = key;
- if (HASH_LITTLE_ENDIAN && ((u.i & 0x3) == 0)) {
- const uint32_t *k = (const uint32_t *) key; /* read 32-bit chunks */
-
- /*------ all but last block: aligned reads and affect 32 bits of (a,b,c) */
- while (length > 12) {
- a += k[0];
- b += k[1];
- c += k[2];
- mix(a, b, c);
- length -= 12;
- k += 3;
- }
-
- /*----------------------------- handle the last (probably partial) block */
- /*
- * "k[2]&0xffffff" actually reads beyond the end of the string, but
- * then masks off the part it's not allowed to read. Because the
- * string is aligned, the masked-off tail is in the same word as the
- * rest of the string. Every machine with memory protection I've seen
- * does it on word boundaries, so is OK with this. But VALGRIND will
- * still catch it and complain. The masking trick does make the hash
- * noticably faster for short strings (like English words).
- */
-#ifndef VALGRIND
-
- switch (length) {
- case 12: c+=k[2]; b+=k[1]; a+=k[0]; break;
- case 11: c+=k[2]&0xffffff; b+=k[1]; a+=k[0]; break;
- case 10: c+=k[2]&0xffff; b+=k[1]; a+=k[0]; break;
- case 9 : c+=k[2]&0xff; b+=k[1]; a+=k[0]; break;
- case 8 : b+=k[1]; a+=k[0]; break;
- case 7 : b+=k[1]&0xffffff; a+=k[0]; break;
- case 6 : b+=k[1]&0xffff; a+=k[0]; break;
- case 5 : b+=k[1]&0xff; a+=k[0]; break;
- case 4 : a+=k[0]; break;
- case 3 : a+=k[0]&0xffffff; break;
- case 2 : a+=k[0]&0xffff; break;
- case 1 : a+=k[0]&0xff; break;
- case 0 : return c; /* zero length strings require no mixing */
- }
-
-#else /* make valgrind happy */
- {
- const uint8_t *k8;
-
- k8 = (const uint8_t *) k;
- switch (length) {
- case 12: c+=k[2]; b+=k[1]; a+=k[0]; break;
- case 11: c+=((uint32_t) k8[10])<<16; /* fall through */
- case 10: c+=((uint32_t) k8[9])<<8; /* fall through */
- case 9 : c+=k8[8]; /* fall through */
- case 8 : b+=k[1]; a+=k[0]; break;
- case 7 : b+=((uint32_t) k8[6])<<16; /* fall through */
- case 6 : b+=((uint32_t) k8[5])<<8; /* fall through */
- case 5 : b+=k8[4]; /* fall through */
- case 4 : a+=k[0]; break;
- case 3 : a+=((uint32_t) k8[2])<<16; /* fall through */
- case 2 : a+=((uint32_t) k8[1])<<8; /* fall through */
- case 1 : a+=k8[0]; break;
- case 0 : return c;
- }
- }
-#endif /* !valgrind */
-
- } else if (HASH_LITTLE_ENDIAN && ((u.i & 0x1) == 0)) {
- const uint16_t *k = (const uint16_t *) key; /* read 16-bit chunks */
- const uint8_t *k8;
-
- /*--------------- all but last block: aligned reads and different mixing */
- while (length > 12)
- {
- a += k[0] + (((uint32_t) k[1])<<16);
- b += k[2] + (((uint32_t) k[3])<<16);
- c += k[4] + (((uint32_t) k[5])<<16);
- mix(a, b, c);
- length -= 12;
- k += 6;
- }
-
- /*----------------------------- handle the last (probably partial) block */
- k8 = (const uint8_t *) k;
- switch(length)
- {
- case 12: c+=k[4]+(((uint32_t) k[5])<<16);
- b+=k[2]+(((uint32_t) k[3])<<16);
- a+=k[0]+(((uint32_t) k[1])<<16);
- break;
- case 11: c+=((uint32_t) k8[10])<<16; /* fall through */
- case 10: c+=k[4];
- b+=k[2]+(((uint32_t) k[3])<<16);
- a+=k[0]+(((uint32_t) k[1])<<16);
- break;
- case 9 : c+=k8[8]; /* fall through */
- case 8 : b+=k[2]+(((uint32_t) k[3])<<16);
- a+=k[0]+(((uint32_t) k[1])<<16);
- break;
- case 7 : b+=((uint32_t) k8[6])<<16; /* fall through */
- case 6 : b+=k[2];
- a+=k[0]+(((uint32_t) k[1])<<16);
- break;
- case 5 : b+=k8[4]; /* fall through */
- case 4 : a+=k[0]+(((uint32_t) k[1])<<16);
- break;
- case 3 : a+=((uint32_t) k8[2])<<16; /* fall through */
- case 2 : a+=k[0];
- break;
- case 1 : a+=k8[0];
- break;
- case 0 : return c; /* zero length requires no mixing */
- }
-
- } else { /* need to read the key one byte at a time */
- const uint8_t *k = (const uint8_t *)key;
-
- /*--------------- all but the last block: affect some 32 bits of (a, b, c) */
- while (length > 12) {
- a += k[0];
- a += ((uint32_t) k[1])<<8;
- a += ((uint32_t) k[2])<<16;
- a += ((uint32_t) k[3])<<24;
- b += k[4];
- b += ((uint32_t) k[5])<<8;
- b += ((uint32_t) k[6])<<16;
- b += ((uint32_t) k[7])<<24;
- c += k[8];
- c += ((uint32_t) k[9])<<8;
- c += ((uint32_t) k[10])<<16;
- c += ((uint32_t) k[11])<<24;
- mix(a,b,c);
- length -= 12;
- k += 12;
- }
-
- /*-------------------------------- last block: affect all 32 bits of (c) */
- switch (length) { /* all the case statements fall through */
- case 12: c+=((uint32_t) k[11])<<24;
- case 11: c+=((uint32_t) k[10])<<16;
- case 10: c+=((uint32_t) k[9])<<8;
- case 9 : c+=k[8];
- case 8 : b+=((uint32_t) k[7])<<24;
- case 7 : b+=((uint32_t) k[6])<<16;
- case 6 : b+=((uint32_t) k[5])<<8;
- case 5 : b+=k[4];
- case 4 : a+=((uint32_t) k[3])<<24;
- case 3 : a+=((uint32_t) k[2])<<16;
- case 2 : a+=((uint32_t) k[1])<<8;
- case 1 : a+=k[0];
- break;
- case 0 : return c;
- }
- }
-
- final(a, b, c);
- return c;
-}
-
-static inline
-uint32_t jhash(const void *key, size_t length, uint32_t seed)
-{
- return hashlittle(key, length, seed);
-}
projects / lttng-ust.git / blobdiff