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/*-*- Mode: C; c-basic-offset: 8; indent-tabs-mode: nil -*-*/
/***
This file is part of systemd.
Copyright 2013 Lennart Poettering
systemd 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 2.1 of the License, or
(at your option) any later version.
systemd 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 systemd; If not, see <http://www.gnu.org/licenses/>.
***/
#include "bus-bloom.h"
#include "siphash24.h"
#include "util.h"
static inline void set_bit(uint64_t filter[], unsigned long b) {
filter[b >> 6] |= 1ULL << (b & 63);
}
static const sd_id128_t hash_keys[] = {
SD_ID128_ARRAY(b9,66,0b,f0,46,70,47,c1,88,75,c4,9c,54,b9,bd,15),
SD_ID128_ARRAY(aa,a1,54,a2,e0,71,4b,39,bf,e1,dd,2e,9f,c5,4a,3b),
SD_ID128_ARRAY(63,fd,ae,be,cd,82,48,12,a1,6e,41,26,cb,fa,a0,c8),
SD_ID128_ARRAY(23,be,45,29,32,d2,46,2d,82,03,52,28,fe,37,17,f5),
SD_ID128_ARRAY(56,3b,bf,ee,5a,4f,43,39,af,aa,94,08,df,f0,fc,10),
SD_ID128_ARRAY(31,80,c8,73,c7,ea,46,d3,aa,25,75,0f,9e,4c,09,29),
SD_ID128_ARRAY(7d,f7,18,4b,7b,a4,44,d5,85,3c,06,e0,65,53,96,6d),
SD_ID128_ARRAY(f2,77,e9,6f,93,b5,4e,71,9a,0c,34,88,39,25,bf,35),
};
static void bloom_add_data(
uint64_t filter[], /* The filter bits */
size_t size, /* Size of the filter in bytes */
unsigned k, /* Number of hash functions */
const void *data, /* Data to hash */
size_t n) { /* Size of data to hash in bytes */
uint64_t h;
uint64_t m;
unsigned w, i, c = 0;
unsigned hash_index;
assert(size > 0);
assert(k > 0);
/* Determine bits in filter */
m = size * 8;
/* Determine how many bytes we need to generate a bit index 0..m for this filter */
w = (u64log2(m) + 7) / 8;
assert(w <= sizeof(uint64_t));
/* Make sure we have enough hash keys to generate m * k bits
* of hash value. Note that SipHash24 generates 64 bits of
* hash value for each 128 bits of hash key. */
assert(k * w <= ELEMENTSOF(hash_keys) * 8);
for (i = 0, hash_index = 0; i < k; i++) {
uint64_t p = 0;
unsigned d;
for (d = 0; d < w; d++) {
if (c <= 0) {
h = siphash24(data, n, hash_keys[hash_index++].bytes);
c += 8;
}
p = (p << 8ULL) | (uint64_t) ((uint8_t *)&h)[8 - c];
c--;
}
p &= m - 1;
set_bit(filter, p);
}
/* log_debug("bloom: adding <%.*s>", (int) n, (char*) data); */
}
void bloom_add_pair(uint64_t filter[], size_t size, unsigned k, const char *a, const char *b) {
size_t n;
char *c;
assert(filter);
assert(a);
assert(b);
n = strlen(a) + 1 + strlen(b);
c = alloca(n + 1);
strcpy(stpcpy(stpcpy(c, a), ":"), b);
bloom_add_data(filter, size, k, c, n);
}
void bloom_add_prefixes(uint64_t filter[], size_t size, unsigned k, const char *a, const char *b, char sep) {
size_t n;
char *c, *p;
assert(filter);
assert(a);
assert(b);
n = strlen(a) + 1 + strlen(b);
c = alloca(n + 1);
p = stpcpy(stpcpy(c, a), ":");
strcpy(p, b);
bloom_add_data(filter, size, k, c, n);
for (;;) {
char *e;
e = strrchr(p, sep);
if (!e)
break;
*(e + 1) = 0;
bloom_add_data(filter, size, k, c, e - c + 1);
if (e == p)
break;
*e = 0;
bloom_add_data(filter, size, k, c, e - c);
}
}
bool bloom_validate_parameters(size_t size, unsigned k) {
uint64_t m;
unsigned w;
if (size <= 0)
return false;
if (k <= 0)
return false;
m = size * 8;
w = (u64log2(m) + 7) / 8;
if (w > sizeof(uint64_t))
return false;
if (k * w > ELEMENTSOF(hash_keys) * 8)
return false;
return true;
}
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