/* Libiberty realpath.  Like realpath, but more consistent behavior.

   Based on gdb_realpath from GDB.

   Copyright (C) 2003-2025 Free Software Foundation, Inc.

   This file is part of the libiberty library.

   This program is free software; you can redistribute it and/or modify

   it under the terms of the GNU General Public License as published by

   the Free Software Foundation; either version 2 of the License, or

   (at your option) any later version.

   This program is distributed in the hope that it will be useful,

   but WITHOUT ANY WARRANTY; without even the implied warranty of

   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the

   GNU General Public License for more details.

   You should have received a copy of the GNU General Public License

   along with this program; if not, write to the Free Software

   Foundation, Inc., 51 Franklin Street - Fifth Floor,

   Boston, MA 02110-1301, USA.  */

/*

@deftypefn Replacement {const char*} lrealpath (const char *@var{name})

Given a pointer to a string containing a pathname, returns a canonical

version of the filename.  Symlinks will be resolved, and ``.'' and ``..''

components will be simplified.  The returned value will be allocated using

@code{malloc}, or @code{NULL} will be returned on a memory allocation error.

@end deftypefn

*/

#include "config.h"

#include "ansidecl.h"

#include "libiberty.h"

#ifdef HAVE_LIMITS_H

#include <limits.h>

#endif

#ifdef HAVE_STDLIB_H

#include <stdlib.h>

#endif

#ifdef HAVE_UNISTD_H

#include <unistd.h>

#endif

#ifdef HAVE_STRING_H

#include <string.h>

#endif

/* On GNU libc systems the declaration is only visible with _GNU_SOURCE.  */

#if defined(HAVE_CANONICALIZE_FILE_NAME) \

    && defined(NEED_DECLARATION_CANONICALIZE_FILE_NAME)

extern char *canonicalize_file_name (const char *);

#endif

#if defined(HAVE_REALPATH)

# if defined (PATH_MAX)

#  define REALPATH_LIMIT PATH_MAX

# else

#  if defined (MAXPATHLEN)

#   define REALPATH_LIMIT MAXPATHLEN

#  endif

# endif

#else

  /* cygwin has realpath, so it won't get here.  */ 

# if defined (_WIN32)

#  define WIN32_LEAN_AND_MEAN

#  include <windows.h> /* for GetFullPathName/GetFinalPathNameByHandle/

                          CreateFile/CloseHandle */

#  define WIN32_REPLACE_SLASHES(_ptr, _len) \

     for (unsigned i = 0; i != (_len); ++i) \

       if ((_ptr)[i] == '\\') (_ptr)[i] = '/';

#  define WIN32_UNC_PREFIX "//?/UNC/"

#  define WIN32_UNC_PREFIX_LEN (sizeof(WIN32_UNC_PREFIX)-1)

#  define WIN32_IS_UNC_PREFIX(ptr) \

  (0 == memcmp(ptr, WIN32_UNC_PREFIX, WIN32_UNC_PREFIX_LEN))

#  define WIN32_NON_UNC_PREFIX "//?/"

#  define WIN32_NON_UNC_PREFIX_LEN (sizeof(WIN32_NON_UNC_PREFIX)-1)

#  define WIN32_IS_NON_UNC_PREFIX(ptr) \

  (0 == memcmp(ptr, WIN32_NON_UNC_PREFIX, WIN32_NON_UNC_PREFIX_LEN))

/* Get full path name without symlinks resolution.

   It also converts all forward slashes to back slashes.

*/

char* get_full_path_name(const char *filename) {

  DWORD len;

  char *buf, *ptr, *res;

  /* determining the required buffer size.

     from the man: `If the lpBuffer buffer is too small to contain

     the path, the return value is the size, in TCHARs, of the buffer

     that is required to hold the path _and_the_terminating_null_character_`

  */

  len = GetFullPathName(filename, 0, NULL, NULL);

  if ( len == 0 )

    return strdup(filename);

  buf = (char *)malloc(len);

  /* no point to check the result again */

  len = GetFullPathName(filename, len, buf, NULL);

  buf[len] = 0;

  /* replace slashes */

  WIN32_REPLACE_SLASHES(buf, len);

  /* calculate offset based on prefix type */

  len = WIN32_IS_UNC_PREFIX(buf)

    ? (WIN32_UNC_PREFIX_LEN - 2)

    : WIN32_IS_NON_UNC_PREFIX(buf)

      ? WIN32_NON_UNC_PREFIX_LEN

      : 0

  ;

  ptr = buf + len;

  if ( WIN32_IS_UNC_PREFIX(buf) ) {

    ptr[0] = '/';

    ptr[1] = '/';

  }

  res = strdup(ptr);

  free(buf);

  return res;

}

# if _WIN32_WINNT >= 0x0600

/* Get full path name WITH symlinks resolution.

   It also converts all forward slashes to back slashes.

*/

char* get_final_path_name(HANDLE fh) {

  DWORD len;

  char *buf, *ptr, *res;

  /* determining the required buffer size.

     from the  man: `If the function fails because lpszFilePath is too

     small to hold the string plus the terminating null character,

     the return value is the required buffer size, in TCHARs. This

     value _includes_the_size_of_the_terminating_null_character_`.

     but in my testcase I have path with 26 chars, the function

     returns 26 also, ie without the trailing zero-char...

  */

  len = GetFinalPathNameByHandle(

     fh

    ,NULL

    ,0

    ,FILE_NAME_NORMALIZED | VOLUME_NAME_DOS

  );

  if ( len == 0 )

    return NULL;

  len += 1; /* for zero-char */

  buf = (char *)malloc(len);

  /* no point to check the result again */

  len = GetFinalPathNameByHandle(

     fh

    ,buf

    ,len

    ,FILE_NAME_NORMALIZED | VOLUME_NAME_DOS

  );

  buf[len] = 0;

  /* replace slashes */

  WIN32_REPLACE_SLASHES(buf, len);

  /* calculate offset based on prefix type */

  len = WIN32_IS_UNC_PREFIX(buf)

    ? (WIN32_UNC_PREFIX_LEN - 2)

    : WIN32_IS_NON_UNC_PREFIX(buf)

      ? WIN32_NON_UNC_PREFIX_LEN

      : 0

  ;

  ptr = buf + len;

  if ( WIN32_IS_UNC_PREFIX(buf) ) {

    ptr[0] = '/';

    ptr[1] = '/';

  }

  res = strdup(ptr);

  free(buf);

  return res;

}

# endif // _WIN32_WINNT >= 0x0600

# endif // _WIN32

#endif

char *

lrealpath (const char *filename)

{

  /* Method 1: The system has a compile time upper bound on a filename

     path.  Use that and realpath() to canonicalize the name.  This is

     the most common case.  Note that, if there isn't a compile time

     upper bound, you want to avoid realpath() at all costs.  */

#if defined(REALPATH_LIMIT)

  {

    char buf[REALPATH_LIMIT];

    const char *rp = realpath (filename, buf);

    if (rp == NULL)

      rp = filename;

    return strdup (rp);

  }

#endif /* REALPATH_LIMIT */

  /* Method 2: The host system (i.e., GNU) has the function

     canonicalize_file_name() which malloc's a chunk of memory and

     returns that, use that.  */

#if defined(HAVE_CANONICALIZE_FILE_NAME)

  {

    char *rp = canonicalize_file_name (filename);

    if (rp == NULL)

      return strdup (filename);

    else

      return rp;

  }

#endif

  /* Method 3: Now we're getting desperate!  The system doesn't have a

     compile time buffer size and no alternative function.  Query the

     OS, using pathconf(), for the buffer limit.  Care is needed

     though, some systems do not limit PATH_MAX (return -1 for

     pathconf()) making it impossible to pass a correctly sized buffer

     to realpath() (it could always overflow).  On those systems, we

     skip this.  */

#if defined (HAVE_REALPATH) && defined (HAVE_UNISTD_H)

  {

    /* Find out the max path size.  */

    long path_max = pathconf ("/", _PC_PATH_MAX);

    if (path_max > 0)

      {

  /* PATH_MAX is bounded.  */

  char *buf, *rp, *ret;

  buf = (char *) malloc (path_max);

  if (buf == NULL)

    return NULL;

  rp = realpath (filename, buf);

  ret = strdup (rp ? rp : filename);

  free (buf);

  return ret;

      }

  }

#endif

  /* The MS Windows method */

#if defined (_WIN32)

  {

    char *res;

    /* For Windows Vista and greater */

#if _WIN32_WINNT >= 0x0600

    /* For some reason the function receives just empty `filename`, but not NULL.

       What should we do in that case?

       According to `strdup()` implementation

         (https://elixir.bootlin.com/glibc/latest/source/string/strdup.c)

       it will alloc 1 byte even for empty but non NULL string.

       OK, will use `strdup()` for that case.

    */

    if ( 0 == strlen(filename) )

      return strdup(filename);

    HANDLE fh = CreateFile(

       filename

      ,FILE_READ_ATTRIBUTES

      ,FILE_SHARE_READ | FILE_SHARE_WRITE | FILE_SHARE_DELETE

      ,NULL

      ,OPEN_EXISTING

      ,FILE_FLAG_BACKUP_SEMANTICS

      ,NULL

    );

    if ( fh == INVALID_HANDLE_VALUE ) {

      res = get_full_path_name(filename);

    } else {

      res = get_final_path_name(fh);

      CloseHandle(fh);

      if ( !res )

        res = get_full_path_name(filename);

    }

#else

    /* For Windows XP */

    res = get_full_path_name(filename);

#endif // _WIN32_WINNT >= 0x0600

    return res;

  }

#endif // _WIN32

}