/* Read a line from an nss_files database file.

   Copyright (C) 2020 Free Software Foundation, Inc.

   This file is part of the GNU C Library.

   The GNU C 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.

   The GNU C 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 the GNU C Library; if not, see

   <https://www.gnu.org/licenses/>.  */

#include <nss_files.h>

#include <ctype.h>

#include <errno.h>

#include <string.h>

int

__nss_readline (FILE *fp, char *buf, size_t len, off64_t *poffset)

{

  /* We need space for at least one character, the line terminator,

     and the NUL byte.  */

  if (len < 3)

    {

      *poffset = -1;

      __set_errno (ERANGE);

      return ERANGE;

    }

  while (true)

    {

      /* Keep original offset for retries.  */

      *poffset = __ftello64 (fp);

      buf[len - 1] = '\xff';        /* Marker to recognize truncation.  */

      if (fgets_unlocked (buf, len, fp) == NULL)

        {

          if (feof_unlocked (fp))

            {

              __set_errno (ENOENT);

              return ENOENT;

            }

          else

            {

              /* Any other error.  Do not return ERANGE in this case

                 because the caller would retry.  */

              if (errno == ERANGE)

                __set_errno (EINVAL);

              return errno;

            }

        }

      else if (buf[len - 1] != '\xff')

        /* The buffer is too small.  Arrange for re-reading the same

           line on the next call.  */

        return __nss_readline_seek (fp, *poffset);

      /* fgets_unlocked succeeded.  */

      /* Remove leading whitespace.  */

      char *p = buf;

      while (isspace (*p))

        ++p;

      if (*p == '\0' || *p == '#')

        /* Skip empty lines and comments.  */

        continue;

      if (p != buf)

        memmove (buf, p, strlen (p));

      /* Return line to the caller.  */

      return 0;

    }

}

libc_hidden_def (__nss_readline)

int

__nss_readline_seek (FILE *fp, off64_t offset)

{

  if (offset < 0 /* __ftello64 failed.  */

      || __fseeko64 (fp, offset, SEEK_SET) < 0)

    {

      /* Without seeking support, it is not possible to

         re-read the same line, so this is a hard failure.  */

      fseterr_unlocked (fp);

      __set_errno (ESPIPE);

      return ESPIPE;

    }

  else

    {

      __set_errno (ERANGE);

      return ERANGE;

    }

}