dirent.h

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 *           implementations return ENOENT even when the name refers to a
 *           file.]
 * </table>
 * </function>
 */
static DIR *
opendir(
    const char *dirname)
{
  DIR *dirp;
  assert (dirname != NULL);
  
  dirp = (DIR*)malloc (sizeof (struct DIR));
  if (dirp != NULL) {
    char *p;
    
    /* allocate room for directory name */
    dirp->dirname = (char*) malloc (strlen (dirname) + 1 + strlen ("\\*.*"));
    if (dirp->dirname == NULL) {
      /* failed to duplicate directory name.  errno set by malloc() */
      free (dirp);
      return NULL;
    }
    /* Copy directory name while appending directory separator and "*.*".
     * Directory separator is not appended if the name already ends with
     * drive or directory separator.  Directory separator is assumed to be
     * '/' or '\' and drive separator is assumed to be ':'. */
    strcpy (dirp->dirname, dirname);
    p = strchr (dirp->dirname, '\0');
    if (dirp->dirname < p  &&
        *(p - 1) != '\\'  &&  *(p - 1) != '/'  &&  *(p - 1) != ':')
    {
      strcpy (p++, "\\");
    }
# ifdef DIRENT_WIN32_INTERFACE
    strcpy (p, "*"); /*scan files with and without extension in win32*/
# else
    strcpy (p, "*.*"); /*scan files with and without extension in DOS*/
# endif

    /* open stream */
    if (_initdir (dirp) == 0) {
      /* initialization failed */
      free (dirp->dirname);
      free (dirp);
      return NULL;
    }
  }
  return dirp;
}


/*
 * <function name="readdir">
 * <intro>read a directory entry
 * <syntax>struct dirent *readdir (DIR *dirp);
 *
 * <desc>Read individual directory entry and return pointer to a structure
 * containing the name of the entry.  Individual directory entries returned
 * include normal files, sub-directories, pseudo-directories "." and ".."
 * and also volume labels, hidden files and system files in MS-DOS and
 * MS-Windows.   You might want to use stat(2) function to determinate which
 * one are you dealing with.  Many dirent implementations already contain
 * equivalent information in dirent structure but you cannot depend on
 * this.
 *
 * The dirent structure contains several system dependent fields that
 * generally have no interest to you.  The only interesting one is char
 * d_name[] that is also portable across different systems.  The d_name
 * field contains the name of the directory entry without leading path.
 * While d_name is portable across different systems the actual storage
 * capacity of d_name varies from system to system and there is no portable
 * way to find out it at compile time as different systems define the
 * capacity of d_name with different macros and some systems do not define
 * capacity at all (besides actual declaration of the field). If you really
 * need to find out storage capacity of d_name then you might want to try
 * NAME_MAX macro. The NAME_MAX is defined in POSIX standard althought
 * there are many MS-DOS and MS-Windows implementations those do not define
 * it.  There are also systems that declare d_name as "char d_name[1]" and
 * then allocate suitable amount of memory at run-time.  Thanks to Alain
 * Decamps ([e-mail]) for pointing it out to me.
 *
 * This all leads to the fact that it is difficult to allocate space
 * for the directory names when the very same program is being compiled on
 * number of operating systems.  Therefore I suggest that you always
 * allocate space for directory names dynamically.
 *
 * <ret>
 * Returns a pointer to a structure containing name of the directory entry
 * in `d_name' field or NULL if there was an error.  In case of an error the
 * global `errno' variable will set as follows:
 *
 * <table>
 * [EBADF  |dir parameter refers to an invalid directory stream.  This value
 *          is not set reliably on all implementations.]
 * </table>
 * </function>
 */
static struct dirent *
readdir (DIR *dirp)
{
  assert (dirp != NULL);
  if (dirp == NULL) {
    errno = EBADF;
    return NULL;
  }

#if defined(DIRENT_WIN32_INTERFACE)
  if (dirp->search_handle == INVALID_HANDLE_VALUE) {
    /* directory stream was opened/rewound incorrectly or it ended normally */
    errno = EBADF;
    return NULL;
  }
#endif

  if (dirp->dirent_filled != 0) {
    /*
     * Directory entry has already been retrieved and there is no need to
     * retrieve a new one.  Directory entry will be retrieved in advance
     * when the user calls readdir function for the first time.  This is so
     * because real dirent has separate functions for opening and reading
     * the stream whereas Win32 and DOS dirents open the stream
     * automatically when we retrieve the first file.  Therefore, we have to
     * save the first file when opening the stream and later we have to
     * return the saved entry when the user tries to read the first entry.
     */
    dirp->dirent_filled = 0;
  } else {
    /* fill in entry and return that */
#if defined(DIRENT_WIN32_INTERFACE)
    if (FindNextFile (dirp->search_handle, &dirp->current.data) == FALSE) {
      /* Last file has been processed or an error occured */
      FindClose (dirp->search_handle);
      dirp->search_handle = INVALID_HANDLE_VALUE;
      errno = ENOENT;
      return NULL;
    }

# elif defined(DIRENT_MSDOS_INTERFACE)
    if (_dos_findnext (&dirp->current.data) != 0) {
      /* _dos_findnext and findnext will set errno to ENOENT when no
       * more entries could be retrieved. */
      return NULL;
    }
# endif

    _setdirname (dirp);
    assert (dirp->dirent_filled == 0);
  }
  return &dirp->current;
}


/*
 * <function name="closedir">
 * <intro>close directory stream.
 * <syntax>int closedir (DIR *dirp);
 *
 * <desc>Close directory stream opened by the `opendir' function.  Close of
 * directory stream invalidates the DIR structure as well as previously read
 * dirent entry.
 *
 * <ret>The function typically returns 0 on success and -1 on failure but
 * the function may be declared to return void on same systems.  At least
 * Borland C/C++ and some UNIX implementations use void as a return type.
 * The dirent wrapper tries to define VOID_CLOSEDIR whenever closedir is
 * known to return nothing.  The very same definition is made by the GNU
 * autoconf if you happen to use it.
 *
 * The global `errno' variable will set to EBADF in case of error.
 * </function>
 */
static int
closedir (DIR *dirp)
{   
  int retcode = 0;

  /* make sure that dirp points to legal structure */
  assert (dirp != NULL);
  if (dirp == NULL) {
    errno = EBADF;
    return -1;
  }
 
  /* free directory name and search handles */
  if (dirp->dirname != NULL) free (dirp->dirname);

#if defined(DIRENT_WIN32_INTERFACE)
  if (dirp->search_handle != INVALID_HANDLE_VALUE) {
    if (FindClose (dirp->search_handle) == FALSE) {
      /* Unknown error */
      retcode = -1;
      errno = EBADF;
    }
  }
#endif                     

  /* clear dirp structure to make sure that it cannot be used anymore*/
  memset (dirp, 0, sizeof (*dirp));
# if defined(DIRENT_WIN32_INTERFACE)
  dirp->search_handle = INVALID_HANDLE_VALUE;
# endif

  free (dirp);
  return retcode;
}


/*
 * <function name="rewinddir">
 * <intro>rewind directory stream to the beginning
 * <syntax>void rewinddir (DIR *dirp);
 *
 * <desc>Rewind directory stream to the beginning so that the next call of
 * readdir() returns the very first directory entry again.  However, note
 * that next call of readdir() may not return the same directory entry as it
 * did in first time.  The directory stream may have been affected by newly
 * created files.
 *
 * Almost every dirent implementation ensure that rewinddir will update
 * the directory stream to reflect any ptrLog->logMessages made to the directory entries
 * since the previous ``opendir'' or ``rewinddir'' call.  Keep an eye on
 * this if your program depends on the feature.  I know at least one dirent
 * implementation where you are required to close and re-open the stream to
 * see the ptrLog->logMessages.
 *
 * <ret>Returns nothing.  If something went wrong while rewinding, you will
 * notice it later when you try to retrieve the first directory entry.
 */
static void
rewinddir (DIR *dirp)
{   
  /* make sure that dirp is legal */
  assert (dirp != NULL);
  if (dirp == NULL) {
    errno = EBADF;
    return;
  }
  assert (dirp->dirname != NULL);
  
  /* close previous stream */
#if defined(DIRENT_WIN32_INTERFACE)
  if (dirp->search_handle != INVALID_HANDLE_VALUE) {
    if (FindClose (dirp->search_handle) == FALSE) {
      /* Unknown error */
      errno = EBADF;
    }
  }
#endif

  /* re-open previous stream */
  if (_initdir (dirp) == 0) {
    /* initialization failed but we cannot deal with error.  User will notice
     * error later when she tries to retrieve first directory enty. */
    /*EMPTY*/;
  }
}


/*
 * Open native directory stream object and retrieve first file.
 * Be sure to close previous stream before opening new one.
 */
static int
_initdir (DIR *dirp)
{ 
  assert (dirp != NULL);
  assert (dirp->dirname != NULL);
  dirp->dirent_filled = 0;

# if defined(DIRENT_WIN32_INTERFACE)
  /* Open stream and retrieve first file */
  dirp->search_handle = FindFirstFile (dirp->dirname, &dirp->current.data);
  if (dirp->search_handle == INVALID_HANDLE_VALUE) {
    /* something went wrong but we don't know what.  GetLastError() could
     * give us more information about the error, but then we should map
     * the error code into errno. */
    errno = ENOENT;
    return 0;
  }

# elif defined(DIRENT_MSDOS_INTERFACE)
  if (_dos_findfirst (dirp->dirname,
          _A_SUBDIR | _A_RDONLY | _A_ARCH | _A_SYSTEM | _A_HIDDEN,
          &dirp->current.data) != 0)
  {
    /* _dos_findfirst and findfirst will set errno to ENOENT when no 
     * more entries could be retrieved. */
    return 0;
  }
# endif

  /* initialize DIR and it's first entry */
  _setdirname (dirp);
  dirp->dirent_filled = 1;
  return 1;
}


/*
 * Return implementation dependent name of the current directory entry.
 */
static const char *
_getdirname (const struct dirent *dp)
{
#if defined(DIRENT_WIN32_INTERFACE)
  return dp->data.cFileName;
  
#elif defined(DIRENT_USE_FFBLK)
  return dp->data.ff_name;
  
#else
  return dp->data.name;
#endif  
}


/*
 * Copy name of implementation dependent directory entry to the d_name field.
 */
static void
_setdirname (struct DIR *dirp) {
  /* make sure that d_name is long enough */
  assert (strlen (_getdirname (&dirp->current)) <= NAME_MAX);
  
  strncpy (dirp->current.d_name,
      _getdirname (&dirp->current),
      NAME_MAX);
  dirp->current.d_name[NAME_MAX] = '\0'; /*char d_name[NAME_MAX+1]*/
}
  
# ifdef __cplusplus
}
# endif
# define NAMLEN(dp) ((int)(strlen((dp)->d_name)))

#else
# error "missing dirent interface"
#endif


#endif /*DIRENT_H*/