gnulib/import/getcwd-lgpl.c

   1 /* Copyright (C) 2011-2019 Free Software Foundation, Inc.
   2    This file is part of gnulib.
   3
   4    This program is free software: you can redistribute it and/or modify
   5    it under the terms of the GNU General Public License as published by
   6    the Free Software Foundation; either version 3 of the License, or
   7    (at your option) any later version.
   8
   9    This program 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 General Public License for more details.
  13
  14    You should have received a copy of the GNU 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 char *
  42 rpl_getcwd (char *buf, size_t size)
  43 {
  44   char *ptr;
  45   char *result;
  46
  47   /* Handle single size operations.  */
  48   if (buf)
  49     {
  50       if (!size)
  51         {
  52           errno = EINVAL;
  53           return NULL;
  54         }
  55       return getcwd (buf, size);
  56     }
  57
  58   if (size)
  59     {
  60       buf = malloc (size);
  61       if (!buf)
  62         {
  63           errno = ENOMEM;
  64           return NULL;
  65         }
  66       result = getcwd (buf, size);
  67       if (!result)
  68         {
  69           int saved_errno = errno;
  70           free (buf);
  71           errno = saved_errno;
  72         }
  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     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       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     {
 112       int saved_errno = errno;
 113       free (buf);
 114       errno = saved_errno;
 115     }
 116   else
 117     {
 118       /* Here result == buf.  */
 119       /* Shrink result before returning it.  */
 120       size_t actual_size = strlen (result) + 1;
 121       if (actual_size < size)
 122         {
 123           char *shrinked_result = realloc (result, actual_size);
 124           if (shrinked_result != NULL)
 125             result = shrinked_result;
 126         }
 127     }
 128   return result;
 129 }
 130
 131 #endif