stdlib/grouping.c

   1 /* Internal header for proving correct grouping in strings of numbers.
   2    Copyright (C) 1995-2022 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 <limits.h>
  20 #include <stddef.h>
  21 #include <string.h>
  22
  23 #ifndef MAX
  24 #define MAX(a,b)        ({ typeof(a) _a = (a); typeof(b) _b = (b); \
  25                            _a > _b ? _a : _b; })
  26 #endif
  27
  28 #ifdef USE_WIDE_CHAR
  29 # include <wctype.h>
  30 # define L_(Ch) L##Ch
  31 # define UCHAR_TYPE wint_t
  32 # define STRING_TYPE wchar_t
  33 #else
  34 # define L_(Ch) Ch
  35 # define UCHAR_TYPE unsigned char
  36 # define STRING_TYPE char
  37 #endif
  38
  39 #include "grouping.h"
  40
  41 /* Find the maximum prefix of the string between BEGIN and END which
  42    satisfies the grouping rules.  It is assumed that at least one digit
  43    follows BEGIN directly.  */
  44
  45 const STRING_TYPE *
  46 #ifdef USE_WIDE_CHAR
  47 __correctly_grouped_prefixwc (const STRING_TYPE *begin, const STRING_TYPE *end,
  48                               wchar_t thousands,
  49 #else
  50 __correctly_grouped_prefixmb (const STRING_TYPE *begin, const STRING_TYPE *end,
  51                               const char *thousands,
  52 #endif
  53                               const char *grouping)
  54 {
  55 #ifndef USE_WIDE_CHAR
  56   size_t thousands_len;
  57   int cnt;
  58 #endif
  59
  60   if (grouping == NULL)
  61     return end;
  62
  63 #ifndef USE_WIDE_CHAR
  64   thousands_len = strlen (thousands);
  65 #endif
  66
  67   while (end > begin)
  68     {
  69       const STRING_TYPE *cp = end - 1;
  70       const char *gp = grouping;
  71
  72       /* Check first group.  */
  73       while (cp >= begin)
  74         {
  75 #ifdef USE_WIDE_CHAR
  76           if (*cp == thousands)
  77             break;
  78 #else
  79           if (cp[thousands_len - 1] == *thousands)
  80             {
  81               for (cnt = 1; thousands[cnt] != '\0'; ++cnt)
  82                 if (thousands[cnt] != cp[thousands_len - 1 - cnt])
  83                   break;
  84               if (thousands[cnt] == '\0')
  85                 break;
  86             }
  87 #endif
  88           --cp;
  89         }
  90
  91       /* We allow the representation to contain no grouping at all even if
  92          the locale specifies we can have grouping.  */
  93       if (cp < begin)
  94         return end;
  95
  96       if (end - cp == (int) *gp + 1)
  97         {
  98           /* This group matches the specification.  */
  99
 100           const STRING_TYPE *new_end;
 101
 102           if (cp < begin)
 103             /* There is just one complete group.  We are done.  */
 104             return end;
 105
 106           /* CP points to a thousands separator character.  The preceding
 107              remainder of the string from BEGIN to NEW_END is the part we
 108              will consider if there is a grouping error in this trailing
 109              portion from CP to END.  */
 110           new_end = cp - 1;
 111
 112           /* Loop while the grouping is correct.  */
 113           while (1)
 114             {
 115               /* Get the next grouping rule.  */
 116               ++gp;
 117               if (*gp == 0)
 118                 /* If end is reached use last rule.  */
 119                 --gp;
 120
 121               /* Skip the thousands separator.  */
 122               --cp;
 123
 124               if (*gp == CHAR_MAX
 125 #if CHAR_MIN < 0
 126                   || *gp < 0
 127 #endif
 128                   )
 129                 {
 130                   /* No more thousands separators are allowed to follow.  */
 131                   while (cp >= begin)
 132                     {
 133 #ifdef USE_WIDE_CHAR
 134                       if (*cp == thousands)
 135                         break;
 136 #else
 137                       for (cnt = 0; thousands[cnt] != '\0'; ++cnt)
 138                         if (thousands[cnt] != cp[thousands_len - cnt - 1])
 139                           break;
 140                       if (thousands[cnt] == '\0')
 141                         break;
 142 #endif
 143                       --cp;
 144                     }
 145
 146                   if (cp < begin)
 147                     /* OK, only digits followed.  */
 148                     return end;
 149                 }
 150               else
 151                 {
 152                   /* Check the next group.  */
 153                   const STRING_TYPE *group_end = cp;
 154
 155                   while (cp >= begin)
 156                     {
 157 #ifdef USE_WIDE_CHAR
 158                       if (*cp == thousands)
 159                         break;
 160 #else
 161                       for (cnt = 0; thousands[cnt] != '\0'; ++cnt)
 162                         if (thousands[cnt] != cp[thousands_len - cnt - 1])
 163                           break;
 164                       if (thousands[cnt] == '\0')
 165                         break;
 166 #endif
 167                       --cp;
 168                     }
 169
 170                   if (cp < begin && group_end - cp <= (int) *gp)
 171                     /* Final group is correct.  */
 172                     return end;
 173
 174                   if (cp < begin || group_end - cp != (int) *gp)
 175                     /* Incorrect group.  Punt.  */
 176                     break;
 177                 }
 178             }
 179
 180           /* The trailing portion of the string starting at NEW_END
 181              contains a grouping error.  So we will look for a correctly
 182              grouped number in the preceding portion instead.  */
 183           end = new_end;
 184         }
 185       else
 186         {
 187           /* Even the first group was wrong; determine maximum shift.  */
 188           if (end - cp > (int) *gp + 1)
 189             end = cp + (int) *gp + 1;
 190           else if (cp < begin)
 191             /* This number does not fill the first group, but is correct.  */
 192             return end;
 193           else
 194             /* CP points to a thousands separator character.  */
 195             end = cp;
 196         }
 197     }
 198
 199   return MAX (begin, end);
 200 }