source: vendor/glibc-tests/glibc/stdio-common/test_rdwr.c

/* Copyright (C) 1991,1992,1996,1997,1998,2000 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, write to the Free
   Software Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA
   02111-1307 USA.  */

#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, "/tmp/%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)
      {
        register 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;
}