lib/c_strtod.c

   1 /*
   2  * Locale-independent strtod().
   3  *
   4  * This file may be redistributed under the terms of the
   5  * GNU Lesser General Public License.
   6  *
   7  * Copyright (C) 2021 Karel Zak <kzak@redhat.com>
   8  */
   9 #include "c.h"
  10
  11 #include <locale.h>
  12 #include <stdlib.h>
  13 #include <string.h>
  14
  15 #include "c_strtod.h"
  16
  17 #ifdef __APPLE__
  18 # include <xlocale.h>
  19 #endif
  20
  21 #if defined(HAVE_NEWLOCALE) && (defined(HAVE_STRTOD_L) || defined(HAVE_USELOCALE))
  22 # define USE_CLOCALE
  23 #endif
  24
  25 #if defined(USE_CLOCALE)
  26 static volatile locale_t c_locale;
  27
  28 static locale_t get_c_locale(void)
  29 {
  30         if (!c_locale)
  31                 c_locale = newlocale(LC_ALL_MASK, "C", (locale_t) 0);
  32         return c_locale;
  33 }
  34 #endif
  35
  36
  37 double c_strtod(char const *str, char **end)
  38 {
  39         double res;
  40         int errsv;
  41
  42 #if defined(USE_CLOCALE)
  43         locale_t cl = get_c_locale();
  44
  45 #if defined(HAVE_STRTOD_L)
  46         /*
  47          * A) try strtod_l() for "C" locale
  48          */
  49         if (cl)
  50                 return strtod_l(str, end, cl);
  51 #elif defined(HAVE_USELOCALE)
  52         /*
  53          * B) classic strtod(), but switch to "C" locale by uselocal()
  54          */
  55         if (cl) {
  56                 locale_t org_cl = uselocale(locale);
  57                 if (!org_cl)
  58                         return 0;
  59
  60                 res = strtod(str, end);
  61                 errsv = errno;
  62
  63                 uselocale(org_cl);
  64                 errno = errsv;
  65                 return res;
  66         }
  67 #endif /* HAVE_USELOCALE */
  68 #endif /* USE_CLOCALE */
  69         /*
  70          * C) classic strtod(), but switch to "C" locale by setlocale()
  71          */
  72         char *org_locale = setlocale(LC_NUMERIC, NULL);
  73
  74         if (org_locale) {
  75                 org_locale = strdup(org_locale);
  76                 if (!org_locale)
  77                         return 0;
  78
  79                 setlocale(LC_NUMERIC, "C");
  80         }
  81         res = strtod(str, end);
  82         errsv = errno;
  83
  84         if (org_locale) {
  85                 setlocale(LC_NUMERIC, org_locale);
  86                 free(org_locale);
  87         }
  88         errno = errsv;
  89         return res;
  90 }
  91
  92 #ifdef TEST_PROGRAM
  93 int main(int argc, char *argv[])
  94 {
  95         double res;
  96         char *end;
  97
  98         if (argc < 2) {
  99                 fprintf(stderr, "usage: %s decimal.number\n",
 100                                 program_invocation_short_name);
 101                 return EXIT_FAILURE;
 102         }
 103
 104         res = c_strtod(argv[1], &end);
 105         printf("Result: %g, errno: %d, endptr: '%s'\n", res, errno, end);
 106
 107         return errno ? EXIT_FAILURE : EXIT_SUCCESS;
 108 }
 109 #endif