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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 "util.h"
#include "siphash24.h"
#include "bus-bloom.h"
static inline void set_bit(uint64_t filter[], unsigned b) {
filter[b >> 6] |= 1ULL << (b & 63);
}
#define HASH_KEY1 SD_ID128_MAKE(b9,66,0b,f0,46,70,47,c1,88,75,c4,9c,54,b9,bd,15)
#define HASH_KEY2 SD_ID128_MAKE(aa,a1,54,a2,e0,71,4b,39,bf,e1,dd,2e,9f,c5,4a,3b)
static void bloom_add_data(uint64_t filter[BLOOM_SIZE/8], const void *data, size_t n) {
uint8_t a[8], b[8];
unsigned k = 0;
/*
* Our bloom filter has the following parameters:
*
* m=512 (bits in the filter)
* k=8 (hash functions)
*
* We calculate a two 64bit SipHash values (for two fixed but
* randomly generated hash keys) of which we use 8 parts of 9 bits
* as individual hash functions.
*
*/
siphash24(a, data, n, HASH_KEY1.bytes);
siphash24(b, data, n, HASH_KEY2.bytes);
assert_cc(BLOOM_SIZE*8 == 512);
for (k = 0; k < 8; k++)
set_bit(filter, ((uint16_t) a[k] << 1) ^ (uint16_t) b[k]);
/* log_debug("bloom: adding <%.*s>", (int) n, (char*) data); */
}
void bloom_add_pair(uint64_t filter[BLOOM_SIZE/8], 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, c, n);
}
void bloom_add_prefixes(uint64_t filter[BLOOM_SIZE/8], 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);
for (;;) {
char *e;
e = strrchr(p, sep);
if (!e || e == p)
break;
*e = 0;
bloom_add_data(filter, c, e - c);
}
}
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