src/lrealpath.c

   1 /*!
   2  * \file src/lrealpath.c
   3  *
   4  * \brief Libiberty realpath.
   5  *
   6  * Like realpath, but more consistent behavior.
   7  *
   8  * Based on gdb_realpath from GDB.
   9  *
  10  * Copyright 2003 Free Software Foundation, Inc.
  11  *
  12  * This file is part of the libiberty library.
  13  *
  14  * This program is free software; you can redistribute it and/or modify
  15  * it under the terms of the GNU General Public License as published by
  16  * the Free Software Foundation; either version 2 of the License, or
  17  * (at your option) any later version.
  18  *
  19  * This program is distributed in the hope that it will be useful,
  20  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  21  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  22  * GNU General Public License for more details.
  23  *
  24  * You should have received a copy of the GNU General Public License
  25  * along with this program; if not, write to the Free Software
  26  * Foundation, Inc., 51 Franklin Street - Fifth Floor,
  27  * Boston, MA 02110-1301, USA.
  28  */
  29
  30 /*
  31
  32 @deftypefn Replacement {const char*} lrealpath (const char *@var{name})
  33
  34 Given a pointer to a string containing a pathname, returns a canonical
  35 version of the filename.  Symlinks will be resolved, and ``.'' and ``..''
  36 components will be simplified.  The returned value will be allocated using
  37 @code{malloc}, or @code{NULL} will be returned on a memory allocation error.
  38
  39 @end deftypefn
  40
  41 */
  42
  43 #include "config.h"
  44 #include "lrealpath.h"
  45
  46 #ifdef HAVE_LIMITS_H
  47 #include <limits.h>
  48 #endif
  49 #ifdef HAVE_STDLIB_H
  50 #include <stdlib.h>
  51 #endif
  52 #ifdef HAVE_UNISTD_H
  53 #include <unistd.h>
  54 #endif
  55 #ifdef HAVE_STRING_H
  56 #include <string.h>
  57 #endif
  58
  59 /* On GNU libc systems the declaration is only visible with _GNU_SOURCE.  */
  60 #if defined(HAVE_CANONICALIZE_FILE_NAME) \
  61     && defined(NEED_DECLARATION_CANONICALIZE_FILE_NAME)
  62 extern char *canonicalize_file_name (const char *);
  63 #endif
  64
  65 #if defined(HAVE_REALPATH)
  66 # if defined (PATH_MAX)
  67 #  define REALPATH_LIMIT PATH_MAX
  68 # else
  69 #  if defined (MAXPATHLEN)
  70 #   define REALPATH_LIMIT MAXPATHLEN
  71 #  endif
  72 # endif
  73 #else
  74   /* cygwin has realpath, so it won't get here.  */
  75 # if defined (_WIN32)
  76 #  define WIN32_LEAN_AND_MEAN
  77 #  include <windows.h> /* for GetFullPathName */
  78 # endif
  79 #endif
  80
  81 /*!
  82  * \brief A well-defined realpath () that is always compiled in.
  83  */
  84 char *
  85 lrealpath (const char *filename)
  86 {
  87   /* Method 1: The system has a compile time upper bound on a filename
  88      path.  Use that and realpath() to canonicalize the name.  This is
  89      the most common case.  Note that, if there isn't a compile time
  90      upper bound, you want to avoid realpath() at all costs.  */
  91 #if defined(REALPATH_LIMIT)
  92   {
  93     char buf[REALPATH_LIMIT];
  94     const char *rp = realpath (filename, buf);
  95     if (rp == NULL)
  96       rp = filename;
  97     return strdup (rp);
  98   }
  99   /* REALPATH_LIMIT */
 100
 101   /* Method 2: The host system (i.e., GNU) has the function
 102      canonicalize_file_name() which malloc's a chunk of memory and
 103      returns that, use that.  */
 104 #elif defined(HAVE_CANONICALIZE_FILE_NAME)
 105   {
 106     char *rp = canonicalize_file_name (filename);
 107     if (rp == NULL)
 108       return strdup (filename);
 109     else
 110       return rp;
 111   }
 112   /* HAVE_CANONICALIZE_FILE_NAME */
 113
 114   /* Method 3: Now we're getting desperate!  The system doesn't have a
 115      compile time buffer size and no alternative function.  Query the
 116      OS, using pathconf(), for the buffer limit.  Care is needed
 117      though, some systems do not limit PATH_MAX (return -1 for
 118      pathconf()) making it impossible to pass a correctly sized buffer
 119      to realpath() (it could always overflow).  On those systems, we
 120      skip this.  */
 121 #elif defined (HAVE_REALPATH) && defined (HAVE_UNISTD_H)
 122   {
 123     /* Find out the max path size.  */
 124     long path_max = pathconf ("/", _PC_PATH_MAX);
 125     if (path_max > 0)
 126       {
 127         /* PATH_MAX is bounded.  */
 128         char *buf, *rp, *ret;
 129         buf = (char *) malloc (path_max);
 130         if (buf == NULL)
 131           return NULL;
 132         rp = realpath (filename, buf);
 133         ret = strdup (rp ? rp : filename);
 134         free (buf);
 135         return ret;
 136       }
 137   }
 138   /* HAVE_REALPATH && HAVE_UNISTD_H */
 139
 140   /* The MS Windows method.  If we don't have realpath, we assume we
 141      don't have symlinks and just canonicalize to a Windows absolute
 142      path.  GetFullPath converts ../ and ./ in relative paths to
 143      absolute paths, filling in current drive if one is not given
 144      or using the current directory of a specified drive (eg, "E:foo").
 145      It also converts all forward slashes to back slashes.  */
 146 #elif defined (_WIN32)
 147   {
 148     char buf[MAX_PATH];
 149     char* basename;
 150     DWORD len = GetFullPathName (filename, MAX_PATH, buf, &basename);
 151     if (len == 0 || len > MAX_PATH - 1)
 152       return strdup (filename);
 153     else
 154       {
 155         /* The file system is case-preserving but case-insensitive,
 156            Canonicalize to lowercase, using the codepage associated
 157            with the process locale.  */
 158         CharLowerBuff (buf, len);
 159         return strdup (buf);
 160       }
 161   }
 162 #else
 163
 164   /* This system is a lost cause, just duplicate the filename.  */
 165   return strdup (filename);
 166 #endif
 167 }