complete 'cgpt show' and refactor for incoming commands.

src/platform/vboot_reference/utility/cgpt/cgpt_attribute.c

 /* Copyright (c) 2010 The Chromium OS Authors. All rights reserved.
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  *
  * Update GPT attribute bits.
  */
 #include <getopt.h>
 #include <stdio.h>
 #include <stdlib.h>
 #include "cgpt.h"
@@ skipping 81 matching lines @@
                      attribute_options_details))
     return CGPT_FAILED;
   if (help != NOT_INITED) {
     AttributeHelp();
     return CGPT_FAILED;
   }
 
   if (CGPT_OK != OpenDriveInLastArgument(argc, argv, &drive))
     return CGPT_FAILED;
 
+  if (CheckValid(&drive) != CGPT_OK) return CGPT_FAILED;
+
   debug("[OPTION] i:%d b:%d s:%d t:%d p:%d\n", partition, bad, successful, tries, priority);  /* FIXME */
 
   /* partition is not specified, search for the first Chromeos kernel. */
   if (partition == NOT_INITED) {
     int i;
     for (i = 0; i < GetNumberOfEntries(&drive.gpt); ++i) {
       static Guid chromeos_kernel = GPT_ENT_TYPE_CHROMEOS_KERNEL;
       GptEntry *entry;
       entry = GetEntry(&drive.gpt, PRIMARY, i);
       if (!Memcmp(&chromeos_kernel, &entry->type, sizeof(Guid))) {
@@ skipping 26 matching lines @@
   RepairHeader(&drive.gpt, MASK_PRIMARY);
   /* Forces headers and entries are modified so that CRC32 will be re-calculated
    * and headers and entries will be updated to drive. */
   drive.gpt.modified |= (GPT_MODIFIED_HEADER1 | GPT_MODIFIED_ENTRIES1 |
                          GPT_MODIFIED_HEADER2 | GPT_MODIFIED_ENTRIES2);
   UpdateCrc(&drive.gpt);
   DriveClose(&drive);
 
   return CGPT_OK;
 }