/* Copyright (C) 1991-2018 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

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

#include <errno.h>

#include <stdio.h>

#include <stdlib.h>

#include <string.h>

int

main (int argc, char **argv)

{

  static const char hello[] = "Hello, world.\n";

  static const char replace[] = "Hewwo, world.\n";

  static const size_t replace_from = 2, replace_to = 4;

  char filename[FILENAME_MAX];

  char *name = strrchr (*argv, '/');

  char buf[BUFSIZ];

  FILE *f;

  int lose = 0;

  if (name != NULL)

    ++name;

  else

    name = *argv;

  (void) sprintf (filename, OBJPFX "%s.test", name);

  f = fopen (filename, "w+");

  if (f == NULL)

    {

      perror (filename);

      exit (1);

    }

  (void) fputs (hello, f);

  rewind (f);

  (void) fgets (buf, sizeof (buf), f);

  rewind (f);

  (void) fputs (buf, f);

  rewind (f);

  {

    size_t i;

    for (i = 0; i < replace_from; ++i)

      {

	int c = getc (f);

	if (c == EOF)

	  {

	    printf ("EOF at %Zu.\n", i);

	    lose = 1;

	    break;

	  }

	else if (c != hello[i])

	  {

	    printf ("Got '%c' instead of '%c' at %Zu.\n",

		    (unsigned char) c, hello[i], i);

	    lose = 1;

	    break;

	  }

      }

  }

  {

    long int where = ftell (f);

    if (where == (long int) replace_from)

      {

	size_t i;

	for (i = replace_from; i < replace_to; ++i)

	  if (putc(replace[i], f) == EOF)

	    {

	      printf ("putc('%c') got %s at %Zu.\n",

		      replace[i], strerror (errno), i);

	      lose = 1;

	      break;

	    }

      }

    else if (where == -1L)

      {

	printf ("ftell got %s (should be at %Zu).\n",

		strerror (errno), replace_from);

	lose = 1;

      }

    else

      {

	printf ("ftell returns %lu; should be %Zu.\n", where, replace_from);

	lose = 1;

      }

  }

  if (!lose)

    {

      rewind (f);

      if (fgets (buf, sizeof (buf), f) == NULL)

	{

	  printf ("fgets got %s.\n", strerror(errno));

	  lose = 1;

	}

      else if (strcmp (buf, replace))

	{

	  printf ("Read \"%s\" instead of \"%s\".\n", buf, replace);

	  lose = 1;

	}

    }

  if (lose)

    printf ("Test FAILED!  Losing file is \"%s\".\n", filename);

  else

    {

      (void) remove (filename);

      puts ("Test succeeded.");

    }

  return lose ? EXIT_FAILURE : EXIT_SUCCESS;

}