resolv/ns_samebinaryname.c

   1 /* Compare two binary domain names for quality.
   2    Copyright (C) 2022-2024 Free Software Foundation, Inc.
   3    This file is part of the GNU C Library.
   4
   5    The GNU C Library is free software; you can redistribute it and/or
   6    modify it under the terms of the GNU Lesser General Public
   7    License as published by the Free Software Foundation; either
   8    version 2.1 of the License, or (at your option) any later version.
   9
  10    The GNU C Library is distributed in the hope that it will be useful,
  11    but WITHOUT ANY WARRANTY; without even the implied warranty of
  12    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  13    Lesser General Public License for more details.
  14
  15    You should have received a copy of the GNU Lesser General Public
  16    License along with the GNU C Library; if not, see
  17    <https://www.gnu.org/licenses/>.  */
  18
  19 #include <arpa/nameser.h>
  20 #include <stdbool.h>
  21
  22 /* Convert ASCII letters to upper case.  */
  23 static inline int
  24 ascii_toupper (unsigned char ch)
  25 {
  26   if (ch >= 'a' && ch <= 'z')
  27     return ch - 'a' + 'A';
  28   else
  29     return ch;
  30 }
  31
  32 bool
  33 __ns_samebinaryname (const unsigned char *a, const unsigned char *b)
  34 {
  35   while (*a != 0 && *b != 0)
  36     {
  37       if (*a != *b)
  38         /* Different label length.  */
  39         return false;
  40       int labellen = *a;
  41       ++a;
  42       ++b;
  43       for (int i = 0; i < labellen; ++i)
  44         {
  45           if (*a != *b && ascii_toupper (*a) != ascii_toupper (*b))
  46             /* Different character in label.  */
  47             return false;
  48           ++a;
  49           ++b;
  50         }
  51     }
  52
  53   /* Match if both names are at the root label.  */
  54   return *a == 0 && *b == 0;
  55 }