stdlib/grouping.c

   1 /* Internal header for proving correct grouping in strings of numbers.
   2    Copyright (C) 1995-2024 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 <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   if (grouping == NULL)
  56     return end;
  57
  58 #ifdef USE_WIDE_CHAR
  59   size_t thousands_len = 1;
  60 #else
  61   size_t thousands_len = strlen (thousands);
  62 #endif
  63
  64   while (end - begin >= thousands_len)
  65     {
  66       const STRING_TYPE *cp = end - thousands_len;
  67       const char *gp = grouping;
  68
  69       /* Check first group.  */
  70       while (cp >= begin)
  71         {
  72 #ifdef USE_WIDE_CHAR
  73           if (*cp == thousands)
  74             break;
  75 #else
  76           if (memcmp (cp, thousands, thousands_len) == 0)
  77             break;
  78 #endif
  79           --cp;
  80         }
  81
  82       /* We allow the representation to contain no grouping at all even if
  83          the locale specifies we can have grouping.  */
  84       if (cp < begin)
  85         return end;
  86
  87       if (end - cp == (int) *gp + thousands_len)
  88         {
  89           /* This group matches the specification.  */
  90
  91           const STRING_TYPE *new_end;
  92
  93           if (cp < begin)
  94             /* There is just one complete group.  We are done.  */
  95             return end;
  96
  97           /* CP points to a thousands separator character.  The preceding
  98              remainder of the string from BEGIN to NEW_END is the part we
  99              will consider if there is a grouping error in this trailing
 100              portion from CP to END.  */
 101           new_end = cp;
 102
 103           /* Loop while the grouping is correct.  */
 104           while (1)
 105             {
 106               /* Get the next grouping rule.  */
 107               ++gp;
 108               if (*gp == 0)
 109                 /* If end is reached use last rule.  */
 110                 --gp;
 111
 112               /* Skip the thousands separator.  */
 113               --cp;
 114
 115               if (*gp == CHAR_MAX
 116 #if CHAR_MIN < 0
 117                   || *gp < 0
 118 #endif
 119                   )
 120                 {
 121                   /* No more thousands separators are allowed to follow.  */
 122                   while (cp >= begin)
 123                     {
 124 #ifdef USE_WIDE_CHAR
 125                       if (*cp == thousands)
 126                         break;
 127 #else
 128                       if (memcmp (cp, thousands, thousands_len) == 0)
 129                         break;
 130 #endif
 131                       --cp;
 132                     }
 133
 134                   if (cp < begin)
 135                     /* OK, only digits followed.  */
 136                     return end;
 137                 }
 138               else
 139                 {
 140                   /* Check the next group.  */
 141                   const STRING_TYPE *group_end = cp;
 142
 143                   while (cp >= begin)
 144                     {
 145 #ifdef USE_WIDE_CHAR
 146                       if (*cp == thousands)
 147                         break;
 148 #else
 149                       if (memcmp (cp, thousands, thousands_len) == 0)
 150                         break;
 151 #endif
 152                       --cp;
 153                     }
 154
 155                   if (cp < begin && group_end - cp <= (int) *gp + thousands_len - 1)
 156                     /* Final group is correct.  */
 157                     return end;
 158
 159                   if (cp < begin || group_end - cp != (int) *gp + thousands_len - 1)
 160                     /* Incorrect group.  Punt.  */
 161                     break;
 162                 }
 163             }
 164
 165           /* The trailing portion of the string starting at NEW_END
 166              contains a grouping error.  So we will look for a correctly
 167              grouped number in the preceding portion instead.  */
 168           end = new_end;
 169         }
 170       else
 171         {
 172           /* Even the first group was wrong; determine maximum shift.  */
 173           if (end - cp > (int) *gp + thousands_len)
 174             end = cp + (int) *gp + thousands_len;
 175           else if (cp < begin)
 176             /* This number does not fill the first group, but is correct.  */
 177             return end;
 178           else
 179             /* CP points to a thousands separator character.  */
 180             end = cp;
 181         }
 182     }
 183
 184   return MAX (begin, end);
 185 }