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/* -*- Mode: C; tab-width: 4; indent-tabs-mode: t; c-basic-offset: 4 -*- */
/* NetworkManager -- Network link manager
*
* 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; either
* version 2 of the License, or (at your option) any later version.
*
* 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.
*
* (C) Copyright 2017 Red Hat, Inc.
*/
#include "nm-default.h"
#include "nm-hash-utils.h"
#include <stdint.h>
#include "nm-shared-utils.h"
#include "nm-random-utils.h"
/*****************************************************************************/
#define HASH_KEY_SIZE 16u
#define HASH_KEY_SIZE_GUINT ((HASH_KEY_SIZE + sizeof (guint) - 1) / sizeof (guint))
G_STATIC_ASSERT (sizeof (guint) * HASH_KEY_SIZE_GUINT >= HASH_KEY_SIZE);
static const guint8 *volatile global_seed = NULL;
static const guint8 *
_get_hash_key_init (void)
{
static gsize g_lock;
/* the returned hash is aligned to guin64, hence, it is safe
* to use it as guint* or guint64* pointer. */
static union {
guint8 v8[HASH_KEY_SIZE];
} g_arr _nm_alignas (guint64);
const guint8 *g;
union {
guint8 v8[HASH_KEY_SIZE];
guint vuint;
} t_arr;
again:
g = g_atomic_pointer_get (&global_seed);
if (G_LIKELY (g != NULL)) {
nm_assert (g == g_arr.v8);
return g;
}
{
CSipHash siph_state;
uint64_t h;
/* initialize a random key in t_arr. */
nm_utils_random_bytes (&t_arr, sizeof (t_arr));
/* use siphash() of the key-size, to mangle the first guint. Otherwise,
* the first guint has only the entropy that nm_utils_random_bytes()
* generated for the first 4 bytes and relies on a good random generator.
*
* The first int is especially interesting for nm_hash_static() below, and we
* want to have it all the entropy of t_arr. */
c_siphash_init (&siph_state, t_arr.v8);
c_siphash_append (&siph_state, (const guint8 *) &t_arr, sizeof (t_arr));
h = c_siphash_finalize (&siph_state);
if (sizeof (guint) < sizeof (h))
t_arr.vuint = t_arr.vuint ^ ((guint) (h & 0xFFFFFFFFu)) ^ ((guint) (h >> 32));
else
t_arr.vuint = t_arr.vuint ^ ((guint) (h & 0xFFFFFFFFu));
}
if (!g_once_init_enter (&g_lock)) {
/* lost a race. The random key is already initialized. */
goto again;
}
memcpy (g_arr.v8, t_arr.v8, HASH_KEY_SIZE);
g = g_arr.v8;
g_atomic_pointer_set (&global_seed, g);
g_once_init_leave (&g_lock, 1);
return g;
}
#define _get_hash_key() \
({ \
const guint8 *_g; \
\
_g = g_atomic_pointer_get (&global_seed); \
if (G_UNLIKELY (!_g)) \
_g = _get_hash_key_init (); \
_g; \
})
guint
nm_hash_static (guint static_seed)
{
/* note that we only xor the static_seed with the key.
* We don't use siphash, which would mix the bits better.
* Note that this doesn't matter, because static_seed is not
* supposed to be a value that you are hashing (for that, use
* full siphash).
* Instead, different callers may set a different static_seed
* so that nm_hash_str(NULL) != nm_hash_ptr(NULL).
*
* Also, ensure that we don't return zero.
*/
return ((*((const guint *) _get_hash_key ())) ^ static_seed)
?: static_seed ?: 3679500967u;
}
void
nm_hash_siphash42_init (CSipHash *h, guint static_seed)
{
const guint8 *g;
guint seed[HASH_KEY_SIZE_GUINT];
nm_assert (h);
g = _get_hash_key ();
memcpy (seed, g, HASH_KEY_SIZE);
seed[0] ^= static_seed;
c_siphash_init (h, (const guint8 *) seed);
}
guint
nm_hash_str (const char *str)
{
NMHashState h;
if (!str)
return nm_hash_static (1867854211u);
nm_hash_init (&h, 1867854211u);
nm_hash_update_str (&h, str);
return nm_hash_complete (&h);
}
guint
nm_str_hash (gconstpointer str)
{
return nm_hash_str (str);
}
guint
nm_hash_ptr (gconstpointer ptr)
{
NMHashState h;
if (!ptr)
return nm_hash_static (2907677551u);
nm_hash_init (&h, 2907677551u);
nm_hash_update (&h, &ptr, sizeof (ptr));
return nm_hash_complete (&h);
}
guint
nm_direct_hash (gconstpointer ptr)
{
return nm_hash_ptr (ptr);
}
/*****************************************************************************/
guint
nm_pstr_hash (gconstpointer p)
{
const char *const*s = p;
if (!s)
return nm_hash_static (101061439u);
return nm_hash_str (*s);
}
gboolean
nm_pstr_equal (gconstpointer a, gconstpointer b)
{
const char *const*s1 = a;
const char *const*s2 = b;
return (s1 == s2)
|| ( s1
&& s2
&& nm_streq0 (*s1, *s2));
}
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