grub2: commands/cmp.c: grub_cmd_cmp()

["Rodrigo Steinmüller Wanderley" <rwanderley@natalnet.br>]

Good Morning!

I'm reading grub2 commands in order to understand the syntax to add new
builtins into it.  When reading the cmp commands I found some points I
couldn't understand, think they are bugs, but maybe some of you guys can
prove me wrong...

I will comment the points I didn't understand here:

static grub_err_t
grub_cmd_cmp (struct grub_arg_list *state __attribute__ ((unused)),
	      int argc, char **args)
{
  /* ... */
  file1 = grub_file_open (args[0]);
  if (! file1)
    return grub_errno;

  file2 = grub_file_open (args[1]);
  if (! file2)
    {
      grub_file_close (file2);

*** Shouldn't we be closing file1 here? ***

      return grub_errno;
    }

  /* ... */

      do
	{
	  int i;
	  rd1 = grub_file_read (file1, buf1, 512);
	  rd2 = grub_file_read (file2, buf2, 512);

	  if (rd1 != rd2)

*** We are returning without closing file1 and file2 ***
	    return 0;

	  for (i = 0; i < 512; i++)
	    {
	      if (buf1[i] != buf2[i])
		{
		  grub_printf ("Differ at the offset %d: 0x%x [%s], 0x%x
[%s]\n",			       i + pos, buf1[i], args[0],
			       buf2[i], args[1]);

		  grub_file_close (file1);
		  grub_file_close (file2);

*** I think here is ok, but wouldn't it be better to use a goto and have
*** a single exit point here?
		  return 0;
		}
	    }
	  pos += 512;
	  
	} while (rd2);
    }

  grub_printf ("The files are identical.\n");

  return 0;
}

What I'm thinking is something like (even though this function still
looks somewhat ugly to me):

static grub_err_t
grub_cmd_cmp (struct grub_arg_list *state __attribute__ ((unused)),
	      int argc, char **args)
{
  grub_file_t file1 = 0;
  grub_file_t file2 = 0;
  grub_err_t err = 0;

  if (argc != 2)
    return grub_error (GRUB_ERR_BAD_ARGUMENT, "two arguments required");

  grub_printf ("Compare `%s' and `%s':\n", args[0],
	       args[1]);

  file1 = grub_file_open (args[0]);
  if (! file1) {
    err = grub_errno;
    goto finish;
  }

  file2 = grub_file_open (args[1]);
  if (! file2)
    {
      err = grub_errno;
      goto finish;
    }

  if (grub_file_size (file1) != grub_file_size (file2))
    grub_printf ("Differ in size: %d [%s], %d [%s]\n", 
		 grub_file_size (file1), args[0], 
		 grub_file_size (file2), args[1]);
  
  else
    {
      char buf1[512];
      char buf2[512];
      grub_ssize_t rd1, rd2;
      grub_uint32_t pos = 0;
     
      do
	{
	  int i;
	  rd1 = grub_file_read (file1, buf1, 512);
	  rd2 = grub_file_read (file2, buf2, 512);

	  if (rd1 != rd2)
	    goto finish;

	  for (i = 0; i < 512; i++)
	    {
	      if (buf1[i] != buf2[i])
		{
		  grub_printf ("Differ at the offset %d: 0x%x [%s], 0x%x
[%s]\n",			       i + pos, buf1[i], args[0],
			       buf2[i], args[1]);

		  goto finish;
		}
	    }
	  pos += 512;
	  
	} while (rd2);
      grub_printf ("The files are identical.\n");
    }

 finish:
  if (file1)
    grub_file_close (file1);
  if (file2)
    grub_file_close (file2);

  return err;
}

Best Regards,
  Rodrigo Steinmuller Wanderley


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