/* readable.c: check if a filename is a readable non-directory file.

Copyright (C) 1993, 95, 96 Karl Berry.

This library is free software; you can redistribute it and/or
modify it under the terms of the GNU Library General Public
License as published by the Free Software Foundation; either
version 2 of the License, or (at your option) any later version.

This library 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
Library General Public License for more details.

You should have received a copy of the GNU Library General Public
License along with this library; if not, write to the Free Software
Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.  */

#include <kpathsea/config.h>
#include <kpathsea/c-stat.h>
#include <kpathsea/readable.h>
#include <kpathsea/tex-hush.h>
#include <kpathsea/truncate.h>


/* If access can read FN, run stat (assigning to stat buffer ST) and
   check that fn is not a directory.  Don't check for just being a
   regular file, as it is potentially useful to read fifo's or some
   kinds of devices.  */

#ifdef __DJGPP__
/* `stat' is way too expensive for such a simple job.  */
#define READABLE(fn, st) \
  (access (fn, R_OK) == 0 && access (fn, D_OK) == -1)
#elif WIN32
#define READABLE(fn, st) \
  (GetFileAttributes(fn) != 0xFFFFFFFF && \
   !(GetFileAttributes(fn) & FILE_ATTRIBUTE_DIRECTORY))
#else
#define READABLE(fn, st) \
  (access (fn, R_OK) == 0 && stat (fn, &(st)) == 0 && !S_ISDIR (st.st_mode))
#endif

/* POSIX invented the brain-damage of not necessarily truncating
   filename components; the system's behavior is defined by the value of
   the symbol _POSIX_NO_TRUNC, but you can't change it dynamically!
   
   Generic const return warning.  See extend-fname.c.  */

string
kpse_readable_file P1C(const_string, name)
{
  struct stat st;
  string ret;
  
  if (READABLE (name, st)) {
    ret = (string) name;

#ifdef ENAMETOOLONG
  } else if (errno == ENAMETOOLONG) {
    ret = kpse_truncate_filename (name);

    /* Perhaps some other error will occur with the truncated name, so
       let's call access again.  */
    if (!READABLE (ret, st))
      { /* Failed.  */
        if (ret != name) free (ret);
        ret = NULL;
      }
#endif /* ENAMETOOLONG */

  } else { /* Some other error.  */
    if (errno == EACCES) { /* Maybe warn them if permissions are bad.  */
      if (!kpse_tex_hush ("readable")) {
        perror (name);
      }
    }
    ret = NULL;
  }
  
  return ret;
}