lib/astrxfrm.c

   1 /* Locale dependent string transformation for comparison.
   2    Copyright (C) 2010-2019 Free Software Foundation, Inc.
   3    Written by Bruno Haible <bruno@clisp.org>, 2010.
   4
   5    This program is free software: you can redistribute it and/or modify it
   6    under the terms of the GNU Lesser General Public License as published
   7    by the Free Software Foundation; either version 3 of the License, or
   8    (at your option) any later version.
   9
  10    This program 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 License
  16    along with this program.  If not, see <https://www.gnu.org/licenses/>.  */
  17
  18 #include <config.h>
  19
  20 /* Specification.  */
  21 #include "astrxfrm.h"
  22
  23 #include <errno.h>
  24 #include <stdlib.h>
  25 #include <string.h>
  26
  27 char *
  28 astrxfrm (const char *s, char *resultbuf, size_t *lengthp)
  29 {
  30   char tmpbuf[4000];
  31   char *result;      /* either == resultbuf or == tmpbuf or freshly allocated
  32                         or NULL.  */
  33   size_t allocated;  /* number of bytes allocated at result */
  34   size_t length;
  35
  36   if (resultbuf != NULL)
  37     {
  38       result = resultbuf;
  39       allocated = *lengthp;
  40     }
  41   else
  42     {
  43       result = NULL;
  44       allocated = 0;
  45     }
  46
  47   {
  48     size_t l = strlen (s);
  49     size_t k;
  50
  51     /* A call to strxfrm costs about 20 times more than a call to strdup of
  52        the result.  Therefore it is worth to try to avoid calling strxfrm
  53        more than once on a given string, by making enough room before calling
  54        strxfrm.  The size of the strxfrm result, k, is likely to be between
  55        l and 3 * l.  */
  56     if (3 * l + 1 > allocated)
  57       {
  58         /* Grow the result buffer.  */
  59         if (3 * l + 1 <= sizeof (tmpbuf))
  60           {
  61             result = tmpbuf;
  62             allocated = sizeof (tmpbuf);
  63           }
  64         else
  65           {
  66             size_t new_allocated;
  67             char *new_result;
  68
  69             new_allocated = 3 * l + 1;
  70             if (new_allocated < 2 * allocated)
  71               new_allocated = 2 * allocated;
  72             new_result = (char *) malloc (new_allocated);
  73             if (new_result != NULL)
  74               {
  75                 allocated = new_allocated;
  76                 result = new_result;
  77               }
  78           }
  79       }
  80
  81     errno = 0;
  82     k = strxfrm (result, s, allocated);
  83     if (errno != 0)
  84       goto fail;
  85     if (k >= allocated)
  86       {
  87         /* Grow the result buffer.  */
  88         if (result != resultbuf && result != tmpbuf)
  89           free (result);
  90         if (k + 1 <= sizeof (tmpbuf))
  91           {
  92             result = tmpbuf;
  93             allocated = sizeof (tmpbuf);
  94           }
  95         else
  96           {
  97             size_t new_allocated;
  98             char *new_result;
  99
 100             new_allocated = k + 1;
 101             new_result = (char *) malloc (new_allocated);
 102             if (new_result == NULL)
 103               goto out_of_memory;
 104             allocated = new_allocated;
 105             result = new_result;
 106           }
 107         /* Here k < allocated.  */
 108
 109         /* Try again.  */
 110         errno = 0;
 111         if (strxfrm (result, s, allocated) != k)
 112           /* strxfrm() is not producing reproducible results.  */
 113           abort ();
 114         if (errno != 0)
 115           goto fail;
 116       }
 117
 118     /* Verify that strxfrm() has NUL-terminated the result.  */
 119     if (result[k] != '\0')
 120       abort ();
 121     length = k + 1;
 122   }
 123
 124   /* Here length > 0.  */
 125
 126   if (result == tmpbuf)
 127     {
 128       if (resultbuf != NULL && length <= *lengthp)
 129         {
 130           memcpy (resultbuf, result, length);
 131           result = resultbuf;
 132         }
 133       else
 134         {
 135           char *memory = (char *) malloc (length);
 136
 137           if (memory == NULL)
 138             goto out_of_memory;
 139           memcpy (memory, result, length);
 140           result = memory;
 141         }
 142     }
 143   else
 144     {
 145       /* Shrink the allocated memory if possible.  */
 146       if (result != resultbuf && length < allocated)
 147         {
 148           if (length <= *lengthp)
 149             {
 150               memcpy (resultbuf, result, length);
 151               free (result);
 152               result = resultbuf;
 153             }
 154           else
 155             {
 156               char *memory = (char *) realloc (result, length);
 157               if (memory != NULL)
 158                 {
 159                   memcpy (memory, result, length);
 160                   result = memory;
 161                 }
 162             }
 163         }
 164     }
 165
 166   *lengthp = length;
 167   return result;
 168
 169  fail:
 170   {
 171     int saved_errno = errno;
 172     if (result != resultbuf && result != tmpbuf)
 173       free (result);
 174     errno = saved_errno;
 175     return NULL;
 176   }
 177
 178  out_of_memory:
 179   errno = ENOMEM;
 180   return NULL;
 181 }