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

   Copyright 1993, 1995, 1996, 2008, 2011, 2012 Karl Berry.
   Copyright 1998, 1999, 2000, 2001, 2005 Olaf Weber.

   This library is free software; you can redistribute it and/or
   modify it under the terms of the GNU Lesser General Public
   License as published by the Free Software Foundation; either
   version 2.1 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
   Lesser General Public License for more details.

   You should have received a copy of the GNU Lesser General Public License
   along with this library; if not, see <http://www.gnu.org/licenses/>.  */

#include <kpathsea/config.h>
#include <kpathsea/c-namemx.h>
#include <kpathsea/c-pathch.h>
#include <kpathsea/c-pathmx.h>
#include <kpathsea/c-stat.h>
#include <kpathsea/pathsearch.h>
#include <kpathsea/readable.h>
#include <kpathsea/tex-hush.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 defined (WIN32)
/* st must be an unsigned int under Windows */
static boolean
READABLE(const_string fn, unsigned int st)
{
  if ((st = GetFileAttributes(fn)) != 0xFFFFFFFF) {
      /* succeeded */
      errno = 0;
  } else {
      switch(GetLastError()) {
      case ERROR_BUFFER_OVERFLOW:
          errno = ENAMETOOLONG;
          break;
      case ERROR_ACCESS_DENIED:
          errno = EACCES;
          break;
      default :
          errno = EIO;          /* meaningless, will make ret=NULL later */
          break;
      }
  }
  return ((st != 0xFFFFFFFF) &&
                  !(st & 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!  */

string
kpathsea_readable_file (kpathsea kpse, string name)
{
#ifdef WIN32
  unsigned int st = 0;
#else /* ! WIN32 */
  struct stat st;
#endif

  kpathsea_normalize_path (kpse, name);
  if (READABLE (name, st)) {
      return name;
#ifdef ENAMETOOLONG
  } else if (errno == ENAMETOOLONG) {
      /* Truncate any too-long components in NAME.  */
      unsigned c_len = 0;        /* Length of current component.  */
      char *s = name;            /* Position in current component.  */
      char *t = name;            /* End of allowed length.  */
      
      for (; *s; s++) {
          if (c_len <= NAME_MAX)
              t = s;
#if defined(WIN32)
          if (IS_KANJI (s)) {
              s++;
              c_len += 2;
              continue;
          }
#endif
          if (IS_DIR_SEP (*s) || IS_DEVICE_SEP (*s)) {
              if (c_len > NAME_MAX) {
                  /* Truncate if past the max for a component.  */
                  memmove (t, s, strlen (s) + 1);
                  s = t;
              }
              /* At a directory delimiter, reset component length.  */
              c_len = 0;
          } else
              c_len++;
      }
      if (c_len > NAME_MAX)
          /* Truncate if past the max for last component.  */
          *t = 0;

      /* Perhaps some other error will occur with the truncated name, so
         let's call access again.  */
      if (READABLE (name, st)) /* Success.  */
          return name;
#endif /* ENAMETOOLONG */
  } else { /* Some other error.  */
      if (errno == EACCES) { /* Maybe warn them if permissions are bad.  */
          if (!kpathsea_tex_hush (kpse, "readable")) {
              perror (name);
          }
      }
  }
  return NULL;
}

#if defined (KPSE_COMPAT_API)
string
kpse_readable_file (string name)
{
    return kpathsea_readable_file (kpse_def, name);
}
#endif