lib/getcwd-lgpl.c

   1 /* Copyright (C) 2011-2024 Free Software Foundation, Inc.
   2    This file is part of gnulib.
   3
   4    This file is free software: you can redistribute it and/or modify
   5    it under the terms of the GNU Lesser General Public License as
   6    published by the Free Software Foundation; either version 2.1 of the
   7    License, or (at your option) any later version.
   8
   9    This file is distributed in the hope that it will be useful,
  10    but WITHOUT ANY WARRANTY; without even the implied warranty of
  11    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  12    GNU Lesser General Public License for more details.
  13
  14    You should have received a copy of the GNU Lesser General Public License
  15    along with this program.  If not, see <https://www.gnu.org/licenses/>.  */
  16
  17 #include <config.h>
  18
  19 /* Specification */
  20 #include <unistd.h>
  21
  22 #include <errno.h>
  23 #include <stdlib.h>
  24 #include <string.h>
  25
  26 #if GNULIB_GETCWD
  27 /* Favor GPL getcwd.c if both getcwd and getcwd-lgpl modules are in use.  */
  28 typedef int dummy;
  29 #else
  30
  31 /* Get the name of the current working directory, and put it in SIZE
  32    bytes of BUF.  Returns NULL if the directory couldn't be determined
  33    (perhaps because the absolute name was longer than PATH_MAX, or
  34    because of missing read/search permissions on parent directories)
  35    or SIZE was too small.  If successful, returns BUF.  If BUF is
  36    NULL, an array is allocated with 'malloc'; the array is SIZE bytes
  37    long, unless SIZE == 0, in which case it is as big as
  38    necessary.  */
  39
  40 # undef getcwd
  41 # if defined _WIN32 && !defined __CYGWIN__
  42 #  define getcwd _getcwd
  43 # endif
  44
  45 char *
  46 rpl_getcwd (char *buf, size_t size)
  47 {
  48   char *result;
  49
  50   /* Handle single size operations.  */
  51   if (buf)
  52     {
  53       /* Check SIZE argument.  */
  54       if (!size)
  55         {
  56           errno = EINVAL;
  57           return NULL;
  58         }
  59       return getcwd (buf, size);
  60     }
  61
  62   if (size)
  63     {
  64       buf = malloc (size);
  65       if (!buf)
  66         {
  67           errno = ENOMEM;
  68           return NULL;
  69         }
  70       result = getcwd (buf, size);
  71       if (!result)
  72         free (buf);
  73       return result;
  74     }
  75
  76   /* Flexible sizing requested.  Avoid over-allocation for the common
  77      case of a name that fits within a 4k page, minus some space for
  78      local variables, to be sure we don't skip over a guard page.  */
  79   {
  80     char tmp[4032];
  81     size = sizeof tmp;
  82     char *ptr = getcwd (tmp, size);
  83     if (ptr)
  84       {
  85         result = strdup (ptr);
  86         if (!result)
  87           errno = ENOMEM;
  88         return result;
  89       }
  90     if (errno != ERANGE)
  91       return NULL;
  92   }
  93
  94   /* My what a large directory name we have.  */
  95   do
  96     {
  97       size <<= 1;
  98       char *ptr = realloc (buf, size);
  99       if (ptr == NULL)
 100         {
 101           free (buf);
 102           errno = ENOMEM;
 103           return NULL;
 104         }
 105       buf = ptr;
 106       result = getcwd (buf, size);
 107     }
 108   while (!result && errno == ERANGE);
 109
 110   if (!result)
 111     free (buf);
 112   else
 113     {
 114       /* Here result == buf.  */
 115       /* Shrink result before returning it.  */
 116       size_t actual_size = strlen (result) + 1;
 117       if (actual_size < size)
 118         {
 119           char *shrinked_result = realloc (result, actual_size);
 120           if (shrinked_result != NULL)
 121             result = shrinked_result;
 122         }
 123     }
 124   return result;
 125 }
 126
 127 #endif