100 lines
2.8 KiB
C
100 lines
2.8 KiB
C
/*-*- Mode: C; c-basic-offset: 8; indent-tabs-mode: nil -*-*/
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/***
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This file is part of systemd.
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Copyright 2013 Lennart Poettering
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systemd is free software; you can redistribute it and/or modify it
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under the terms of the GNU Lesser General Public License as published by
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the Free Software Foundation; either version 2.1 of the License, or
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(at your option) any later version.
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systemd is distributed in the hope that it will be useful, but
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WITHOUT ANY WARRANTY; without even the implied warranty of
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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Lesser General Public License for more details.
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You should have received a copy of the GNU Lesser General Public License
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along with systemd; If not, see <http://www.gnu.org/licenses/>.
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***/
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#include "util.h"
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#include "siphash24.h"
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#include "bus-bloom.h"
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static inline void set_bit(uint64_t filter[], unsigned b) {
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filter[b >> 6] |= 1ULL << (b & 63);
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}
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#define HASH_KEY1 SD_ID128_MAKE(b9,66,0b,f0,46,70,47,c1,88,75,c4,9c,54,b9,bd,15)
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#define HASH_KEY2 SD_ID128_MAKE(aa,a1,54,a2,e0,71,4b,39,bf,e1,dd,2e,9f,c5,4a,3b)
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static void bloom_add_data(uint64_t filter[BLOOM_SIZE/8], const void *data, size_t n) {
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uint8_t a[8], b[8];
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unsigned k = 0;
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/*
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* Our bloom filter has the following parameters:
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*
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* m=512 (bits in the filter)
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* k=8 (hash functions)
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*
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* We calculate a two 64bit SipHash values (for two fixed but
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* randomly generated hash keys) of which we use 8 parts of 9 bits
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* as individual hash functions.
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*
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*/
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siphash24(a, data, n, HASH_KEY1.bytes);
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siphash24(b, data, n, HASH_KEY2.bytes);
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assert_cc(BLOOM_SIZE*8 == 512);
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for (k = 0; k < 8; k++)
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set_bit(filter, ((uint16_t) a[k] << 1) ^ (uint16_t) b[k]);
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/* log_debug("bloom: adding <%.*s>", (int) n, (char*) data); */
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}
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void bloom_add_pair(uint64_t filter[BLOOM_SIZE/8], const char *a, const char *b) {
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size_t n;
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char *c;
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assert(filter);
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assert(a);
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assert(b);
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n = strlen(a) + 1 + strlen(b);
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c = alloca(n + 1);
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strcpy(stpcpy(stpcpy(c, a), ":"), b);
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bloom_add_data(filter, c, n);
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}
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void bloom_add_prefixes(uint64_t filter[BLOOM_SIZE/8], const char *a, const char *b, char sep) {
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size_t n;
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char *c, *p;
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assert(filter);
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assert(a);
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assert(b);
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n = strlen(a) + 1 + strlen(b);
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c = alloca(n + 1);
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p = stpcpy(stpcpy(c, a), ":");
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strcpy(p, b);
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for (;;) {
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char *e;
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e = strrchr(p, sep);
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if (!e || e == p)
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break;
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*e = 0;
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bloom_add_data(filter, c, e - c);
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}
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}
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