/* cmd.c - command to cmp an operating system */
/*
 *  GRUB  --  GRand Unified Bootloader
 *  Copyright (C) 2003,2005,2006,2007  Free Software Foundation, Inc.
 *
 *  GRUB is free software: you can redistribute it and/or modify
 *  it under the terms of the GNU General Public License as published by
 *  the Free Software Foundation, either version 3 of the License, or
 *  (at your option) any later version.
 *
 *  GRUB 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 General Public License for more details.
 *
 *  You should have received a copy of the GNU General Public License
 *  along with GRUB.  If not, see <http://www.gnu.org/licenses/>.
 */

#include <grub/dl.h>
#include <grub/misc.h>
#include <grub/file.h>
#include <grub/mm.h>
#include <grub/gzio.h>
#include <grub/command.h>

#define BUFFER_SIZE 512

static grub_err_t
grub_cmd_cmp (grub_command_t cmd __attribute__ ((unused)),
	      int argc, char **args)
{
  grub_ssize_t rd1, rd2;
  grub_off_t pos;
  grub_file_t file1 = 0;
  grub_file_t file2 = 0;
  char *buf1 = 0;
  char *buf2 = 0;

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

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

  file1 = grub_gzfile_open (args[0], 1);
  file2 = grub_gzfile_open (args[1], 1);
  if (! file1 || ! file2)
    goto cleanup;

  if (grub_file_size (file1) != grub_file_size (file2))
    grub_printf ("Files differ in size: %llu [%s], %llu [%s]\n",
		 (unsigned long long) grub_file_size (file1), args[0],
		 (unsigned long long) grub_file_size (file2), args[1]);
  else
    {
      pos = 0;

      buf1 = grub_malloc (BUFFER_SIZE);
      buf2 = grub_malloc (BUFFER_SIZE);

      if (! buf1 || ! buf2)
        goto cleanup;

      do
	{
	  int i;

	  rd1 = grub_file_read (file1, buf1, BUFFER_SIZE);
	  rd2 = grub_file_read (file2, buf2, BUFFER_SIZE);

	  if (rd1 != rd2)
	    goto cleanup;

	  for (i = 0; i < rd2; i++)
	    {
	      if (buf1[i] != buf2[i])
		{
		  grub_printf ("Files differ at the offset %llu: 0x%x [%s], 0x%x [%s]\n",
			       (unsigned long long) (i + pos), buf1[i], args[0],
			       buf2[i], args[1]);
		  goto cleanup;
		}
	    }
	  pos += BUFFER_SIZE;

	}
      while (rd2);

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

cleanup:

  if (buf1)
    grub_free (buf1);
  if (buf2)
    grub_free (buf2);
  if (file1)
    grub_file_close (file1);
  if (file2)
    grub_file_close (file2);

  return grub_errno;
}

static grub_command_t cmd;

GRUB_MOD_INIT(cmp)
{
  cmd = grub_register_command ("cmp", grub_cmd_cmp,
			       "cmp FILE1 FILE2", "Compare two files.");
}

GRUB_MOD_FINI(cmp)
{
  grub_unregister_command (cmd);
}