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// Part of readsb, a Mode-S/ADSB/TIS message decoder.
//
// icao_filter.c: hashtable for ICAO addresses
//
// Copyright (c) 2019 Michael Wolf <michael@mictronics.de>
//
// This code is based on a detached fork of dump1090-fa.
//
// Copyright (c) 2014,2015 Oliver Jowett <oliver@mutability.co.uk>
//
// This file is free software: you can redistribute it and/or modify
// it under the terms of the GNU General Public License as published by
// the Free Software Foundation, either version 3 of the License, or
// any later version.
//
// This file 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
// General Public License for more details.
//
// You should have received a copy of the GNU General Public License
// along with this program. If not, see <http://www.gnu.org/licenses/>.
#include "readsb.h"
// Open-addressed hash table with linear probing.
// Maintain two tables and switch between them to age out entries.
static uint32_t filterBits;
static uint32_t filterBuckets;
static size_t filterSize;
static uint32_t *icao_filter_a;
static uint32_t *icao_filter_b;
static uint32_t *icao_filter_active;
static uint32_t occupied;
static inline uint32_t filterHash(uint32_t addr) {
return addrHash(addr, filterBits);
}
#define EMPTY 0xFFFFFFFF
#define MINBITS 8
#define MAXBITS 20
void icaoFilterInit() {
filterBits = MINBITS;
filterBuckets = 1ULL << filterBits;
filterSize = filterBuckets * sizeof(uint32_t);
occupied = 0;
sfree(icao_filter_a);
sfree(icao_filter_b);
icao_filter_a = cmalloc(filterSize);
icao_filter_b = cmalloc(filterSize);
memset(icao_filter_a, 0xFF, filterSize);
memset(icao_filter_b, 0xFF, filterSize);
icao_filter_active = icao_filter_a;
}
void icaoFilterDestroy() {
sfree(icao_filter_a);
sfree(icao_filter_b);
}
static void icaoFilterResize(uint32_t bits) {
uint32_t oldBuckets = filterBuckets;
uint32_t *oldActive = icao_filter_active;
uint32_t *oldA = icao_filter_a;
uint32_t *oldB = icao_filter_b;
filterBits = bits;
filterBuckets = 1ULL << filterBits;
filterSize = filterBuckets * sizeof(uint32_t);
if (filterBuckets > 256000)
fprintf(stderr, "icao_filter: changing size to %d!\n", (int) filterBuckets);
icao_filter_a = cmalloc(filterSize);
icao_filter_b = cmalloc(filterSize);
memset(icao_filter_a, 0xFF, filterSize);
memset(icao_filter_b, 0xFF, filterSize);
// reset occupied count
occupied = 0;
icao_filter_active = icao_filter_a;
for (uint32_t i = 0; i < oldBuckets; i++) {
if (oldActive[i] != EMPTY) {
icaoFilterAdd(oldActive[i]);
}
}
sfree(oldA);
sfree(oldB);
}
// call this periodically:
void icaoFilterExpire() {
if (occupied < filterBuckets / 9 && filterBits > MINBITS) {
icaoFilterResize(filterBits - 1);
}
// reset occupied count
occupied = 0;
if (icao_filter_active == icao_filter_a) {
memset(icao_filter_b, 0xFF, filterSize);
icao_filter_active = icao_filter_b;
} else {
memset(icao_filter_a, 0xFF, filterSize);
icao_filter_active = icao_filter_a;
}
}
void icaoFilterAdd(uint32_t addr) {
uint32_t h, h0;
h0 = h = filterHash(addr);
while (icao_filter_active[h] != EMPTY && icao_filter_active[h] != addr) {
h = (h + 1) & (filterBuckets - 1);
if (h == h0) {
fprintf(stderr, "ICAO hash table full, this shouldn't happen\n");
return;
}
}
if (icao_filter_active[h] == EMPTY) {
occupied++;
icao_filter_active[h] = addr;
}
if (occupied > filterBuckets / 3 && filterBits < 20) {
icaoFilterResize(filterBits + 1);
}
}
int icaoFilterTest(uint32_t addr) {
uint32_t h, h0;
h0 = h = filterHash(addr);
while (icao_filter_a[h] != EMPTY && icao_filter_a[h] != addr) {
h = (h + 1) & (filterBuckets - 1);
if (h == h0)
break;
}
if (icao_filter_a[h] == addr)
return 1;
h = h0;
while (icao_filter_b[h] != EMPTY && icao_filter_b[h] != addr) {
h = (h + 1) & (filterBuckets - 1);
if (h == h0)
break;
}
if (icao_filter_b[h] == addr)
return 1;
return 0;
}
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