cosmopolitan/libc/dns/sorthoststxt.c

/*-*- mode:c;indent-tabs-mode:nil;c-basic-offset:2;tab-width:8;coding:utf-8 -*-│
│vi: set net ft=c ts=2 sts=2 sw=2 fenc=utf-8                                :vi│
╞══════════════════════════════════════════════════════════════════════════════╡
│ Copyright 2020 Justine Alexandra Roberts Tunney                              │
│                                                                              │
│ Permission to use, copy, modify, and/or distribute this software for         │
│ any purpose with or without fee is hereby granted, provided that the         │
│ above copyright notice and this permission notice appear in all copies.      │
│                                                                              │
│ THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL                │
│ WARRANTIES WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED                │
│ WARRANTIES OF MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE             │
│ AUTHOR BE LIABLE FOR ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL         │
│ DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR        │
│ PROFITS, WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE OR OTHER               │
│ TORTIOUS ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR             │
│ PERFORMANCE OF THIS SOFTWARE.                                                │
╚─────────────────────────────────────────────────────────────────────────────*/
#include "libc/alg/alg.h"
#include "libc/dns/dns.h"
#include "libc/dns/hoststxt.h"

/**
 * Compares hostnames in HOSTS.TXT table.
 * @see CompareDnsNames(), ParseHostsTxt()
 */
static int cmphoststxt(const struct HostsTxtEntry *e1,
                       const struct HostsTxtEntry *e2, const char *strings) {
  if (e1 == e2) return 0;
  return CompareDnsNames(&strings[e1->name], &strings[e2->name]);
}

/**
 * Compares addresses in HOSTS.TXT table.
 * @see ResolveHostsReverse()
 */
static int cmphostsaddr(const struct HostsTxtEntry *e1,
                        const struct HostsTxtEntry *e2) {
  if (e1 == e2) return 0;
  uint32_t v1 = *((uint32_t *)e1->ip), v2 = *((uint32_t *)e2->ip);
  return (v1 == v2 ? 0 : (v1 > v2 ? 1 : -1));
}

/**
 * Sorts entries in HOSTS.TXT table.
 *
 * This function enables ResolveHostsTxt() to be called so hard-coded
 * hostname lookups take logarithmic time; you can blackhole all the
 * spam you want, in your /etc/hosts file.
 *
 * The sorted order, defined by CompareDnsNames(), also makes it
 * possible to efficiently search for subdomains, once the initial sort
 * is done.
 */
void SortHostsTxt(struct HostsTxt *ht, int sort_by) {
  if (ht->entries.p) {
    if (sort_by == HOSTSTXT_SORTEDBYNAME) {
      qsort_r(ht->entries.p, ht->entries.i, sizeof(*ht->entries.p),
              (void *)cmphoststxt, ht->strings.p);
      ht->sorted_by = HOSTSTXT_SORTEDBYNAME;
    } else {
      qsort(ht->entries.p, ht->entries.i, sizeof(*ht->entries.p),
            (void *)cmphostsaddr);
      ht->sorted_by = HOSTSTXT_SORTEDBYADDR;
    }
  }
}