stdlib/rpmatch.c

   1 /* Determine whether string value is affirmation or negative response
   2    according to current locale's data.
   3    This file is part of the GNU C Library.
   4    Copyright (C) 1996-2021 Free Software Foundation, Inc.
   5
   6    The GNU C Library is free software; you can redistribute it and/or
   7    modify it under the terms of the GNU Lesser General Public
   8    License as published by the Free Software Foundation; either
   9    version 2.1 of the License, or (at your option) any later version.
  10
  11    The GNU C Library is distributed in the hope that it will be useful,
  12    but WITHOUT ANY WARRANTY; without even the implied warranty of
  13    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  14    Lesser General Public License for more details.
  15
  16    You should have received a copy of the GNU Lesser General Public
  17    License along with the GNU C Library; if not, see
  18    <https://www.gnu.org/licenses/>.  */
  19
  20 #include <langinfo.h>
  21 #include <stdlib.h>
  22 #include <regex.h>
  23
  24
  25 /* Match against one of the response patterns, compiling the pattern
  26    first if necessary.  */
  27 static int
  28 try (const char *response,
  29      const int tag, const int match, const int nomatch,
  30      const char **lastp, regex_t *re)
  31 {
  32   const char *pattern = nl_langinfo (tag);
  33   if (pattern != *lastp)
  34     {
  35       /* The pattern has changed.  */
  36       if (*lastp != NULL)
  37         {
  38           /* Free the old compiled pattern.  */
  39           __regfree (re);
  40           *lastp = NULL;
  41         }
  42       /* Compile the pattern and cache it for future runs.  */
  43       if (__regcomp (re, pattern, REG_EXTENDED) != 0)
  44         return -1;
  45       *lastp = pattern;
  46     }
  47
  48   /* Try the pattern.  */
  49   return __regexec (re, response, 0, NULL, 0) == 0 ? match : nomatch;
  50 }
  51
  52 int
  53 rpmatch (const char *response)
  54 {
  55   /* We cache the response patterns and compiled regexps here.  */
  56   static const char *yesexpr, *noexpr;
  57   static regex_t yesre, nore;
  58
  59   return (try (response, YESEXPR, 1, 0, &yesexpr, &yesre) ?:
  60           try (response, NOEXPR, 0, -1, &noexpr, &nore));
  61 }