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/*-*- 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 │
│ │
│ This program 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; version 2 of the License. │
│ │
│ This program 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, write to the Free Software │
│ Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA │
│ 02110-1301 USA │
╚─────────────────────────────────────────────────────────────────────────────*/
#include "libc/bits/safemacros.h"
#include "libc/dns/dns.h"
#include "libc/str/str.h"
forceinline void FindDnsLabel(const char *A, size_t *i, size_t *n) {
while (*i) {
if (A[*i - 1] == '.') {
if (*i == *n) {
--(*n);
} else {
break;
}
}
--(*i);
}
}
/**
* Compares DNS hostnames in reverse lexicographical asciibetical order.
* @return <0, 0, or >0
* @see test/libc/dns/dnsnamecmp_test.c (the code that matters)
*/
int dnsnamecmp(const char *A, const char *B) {
if (A == B) return 0;
size_t n = strlen(A);
size_t m = strlen(B);
if (!n || !m || ((A[n - 1] == '.') ^ (B[m - 1] == '.'))) {
if (n && m && A[n - 1] == '.' && strchr(B, '.')) {
--m;
} else if (n && m && B[m - 1] == '.' && strchr(A, '.')) {
--n;
} else {
return A[n ? n - 1 : 0] - B[m ? m - 1 : 0];
}
}
size_t i = n;
size_t j = m;
bool first = true;
for (;;) {
FindDnsLabel(A, &i, &n);
FindDnsLabel(B, &j, &m);
if (first) {
first = false;
if (!i && j) return 1;
if (!j && i) return -1;
}
int res;
if ((res = strncasecmp(&A[i], &B[j], min(n - i + 1, m - j + 1)))) {
return res;
}
if (!i || !j) {
return i - j;
}
n = i;
m = j;
}
}