#ifndef _LTTNG_HASH_HELPER_H
#define _LTTNG_HASH_HELPER_H
/*
* lttng-hash-helper.h
*
* LTTng hash table helpers.
*
* Copyright (C) 2012 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; only
* 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 <assert.h>
#include <stdint.h>
#include <urcu/compiler.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); \
}
static inline __attribute__((unused))
uint32_t lttng_hash_u32(
const uint32_t *k, /* the key, an array of uint32_t values */
size_t length, /* the length of the key, in uint32_ts */
uint32_t initval) /* the previous hash, or an arbitrary value */
{
uint32_t a, b, c;
/* Set up the internal state */
a = b = c = 0xdeadbeef + (((uint32_t) length) << 2) + initval;
/*----------------------------------------- handle most of the key */
while (length > 3) {
a += k[0];
b += k[1];
c += k[2];
mix(a, b, c);
length -= 3;
k += 3;
}
/*----------------------------------- handle the last 3 uint32_t's */
switch (length) { /* all the case statements fall through */
case 3: c += k[2];
case 2: b += k[1];
case 1: a += k[0];
final(a, b, c);
case 0: /* case 0: nothing left to add */
break;
}
/*---------------------------------------------- report the result */
return c;
}
static inline
void lttng_hashword2(
const uint32_t *k, /* the key, an array of uint32_t values */
size_t length, /* the length of the key, in uint32_ts */
uint32_t *pc, /* IN: seed OUT: primary hash value */
uint32_t *pb) /* IN: more seed OUT: secondary hash value */
{
uint32_t a, b, c;
/* Set up the internal state */
a = b = c = 0xdeadbeef + ((uint32_t) (length << 2)) + *pc;
c += *pb;
/*----------------------------------------- handle most of the key */
while (length > 3) {
a += k[0];
b += k[1];
c += k[2];
mix(a, b, c);
length -= 3;
k += 3;
}
/*----------------------------------- handle the last 3 uint32_t's */
switch (length) { /* all the case statements fall through */
case 3: c += k[2];
case 2: b += k[1];
case 1: a += k[0];
final(a, b, c);
case 0: /* case 0: nothing left to add */
break;
}
/*---------------------------------------------- report the result */
*pc = c;
*pb = b;
}
#if (CAA_BITS_PER_LONG == 32)
static inline
unsigned long lttng_hash_mix(const void *_key, size_t length, unsigned long seed)
{
unsigned int key = (unsigned int) _key;
assert(length == sizeof(unsigned int));
return lttng_hash_u32(&key, 1, seed);
}
#else
static inline
unsigned long lttng_hash_mix(const void *_key, size_t length, unsigned long seed)
{
union {
uint64_t v64;
uint32_t v32[2];
} v;
union {
uint64_t v64;
uint32_t v32[2];
} key;
assert(length == sizeof(unsigned long));
v.v64 = (uint64_t) seed;
key.v64 = (uint64_t) _key;
lttng_hashword2(key.v32, 2, &v.v32[0], &v.v32[1]);
return v.v64;
}
#endif
#endif /* _LTTNG_HASH_HELPER_H */