On 12/3/2011 11:41 AM, Vladimir Serbinenko wrote:
>
>> /* nthibr.c - tests whether an MS Windows system partition is hibernated */
>> /*
>>    *  GRUB  --  GRand Unified Bootloader
>>    *  Copyright (C) 2007,2008,2009,2011  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/types.h>
>> #include<grub/mm.h>
>> #include<grub/disk.h>
>> #include<grub/file.h>
>> #include<grub/misc.h>
>> #include<grub/dl.h>
>> #include<grub/extcmd.h>
>> #include<grub/lib/arg.h>
>> #include<grub/err.h>
>> #include<grub/i18n.h>
>>
>> GRUB_MOD_LICENSE("GPLv3+");
>>
>> /* Define this 'empty' array to let the '-h' and '-u' switches be processed */
>> static const struct grub_arg_option options[] = {
>>     {0, 0, 0, 0, 0, 0}
>> };
>>
> No need for empty array. passing 0 instead of this array works.
I have tried it both ways.  For some reason, passing the empty array 
works, but passing a null pointer doesn't.
That is, when I try the latter, the options '-u' and '-h' are treated as 
regular arguments to the command.
>> static grub_err_t
>> grub_cmd_nthibr (grub_extcmd_context_t ctxt __attribute__ ((unused)),
>>                    int argc, char **args)
>> {
>>     grub_err_t status = GRUB_ERR_NONE;
>>     char *partition_name, *hibr_file_path = 0, hibr_file_magic[5];
>>     grub_size_t name_length;
>>     grub_ssize_t magic_size;
>>     grub_disk_t partition;
>>     grub_file_t hibr_file = 0;
>>
>>     /* Check argument count */
>>     if (!argc)
>>       {
>>         status = grub_error (GRUB_ERR_BAD_ARGUMENT,
>>                              N_("too few arguments specified"));
>>         goto exit;
>>       }
>>     else if (argc>   1)
>>       {
>>         status = grub_error (GRUB_ERR_BAD_ARGUMENT,
>>                              N_("too many arguments specified"));
>>         goto exit;
>>       }
>>
>>     partition_name = args[0];
>>     name_length = grub_strlen (partition_name);
>>
>>     /* Check if partition specifier 'looks right' */
>>     if (partition_name[0] != '(' || partition_name[name_length - 1] != ')')
>>       {
>>         status = grub_error (GRUB_ERR_BAD_FILENAME,
>>                              N_("invalid partition specifier"));
>>         goto exit;
>>       }
>>
> I would recommend adding '(' and ')' if none found rather than giving error.
>>     /* Check if partition actually exists */
>>     partition_name[name_length - 1] = '\0';
>>     partition = grub_disk_open (partition_name + 1);
>>     if (!partition)
>>       {
>>         status = grub_error (GRUB_ERR_UNKNOWN_DEVICE,
>>                              N_("partition not found"));
> No need to run grub_error here. grub_disk_open already sets grub_errno
> and grub_errmsg. Just status = grub_errno is enough.
>>         goto exit;
>>       }
>>     else
>>       {
>>         grub_disk_close (partition);
>>         partition_name[name_length - 1] = ')';
>>       }
>>
> No need for 'else' clause (goto already takes care of it)
>>     /* Build path to 'hiberfil.sys' */
>>     hibr_file_path = grub_malloc (grub_strlen (partition_name)
>>                                   + grub_strlen ("/hiberfil.sys") + 1);
>>     if (!hibr_file_path)
>>       {
>>         status = grub_error (GRUB_ERR_OUT_OF_MEMORY,
>>                              N_("out of memory"));
>>         goto exit;
>>       }
>>     else
>>       {
>>         grub_strcpy (hibr_file_path, partition_name);
>>         grub_strcat (hibr_file_path, "/hiberfil.sys");
>>       }
>>
> Same here (no need for grub_error and else)
>>     /* Try to open 'hiberfil.sys' */
>>     hibr_file = grub_file_open (hibr_file_path);
>>     if (!hibr_file)
>>       {
>>         status = grub_error (GRUB_ERR_FILE_NOT_FOUND,
>>                              N_("'hiberfil.sys' not found"));
> ditto
>>         goto exit;
>>       }
>>
>>     /* Try to read magic number of 'hiberfil.sys' */
>>     magic_size = sizeof (hibr_file_magic) - 1;
>>     grub_memset (hibr_file_magic, 0, sizeof (hibr_file_magic));
>>     if (grub_file_read (hibr_file, hibr_file_magic, magic_size)<   magic_size)
>>       {
>>         status = grub_error (GRUB_ERR_BAD_FILE_TYPE,
>>                              N_("'hiberfil.sys' too small"));
> you need to conditionalize call to grub_error. if (!grub_errno) ...
> since incomplete read may indicate an FS problem in which case you want
> the original error message to remain.
>>         goto exit;
>>       }
>>
>>     /* Return SUCCESS if magic indicates file is active; else return FAILURE */
>>     if (!grub_strncasecmp ("hibr", hibr_file_magic, magic_size))
>>       grub_puts (N_("The system is hibernated."));
>>     else
>>       {
>>         grub_puts (N_("The system is NOT hibernated."));
>>         status = GRUB_ERR_TEST_FAILURE;
>>       }
>>
> We also do grub_error (GRUB_ERR_TEST_FAILURE, "false");
>> exit:
>>     /* Ensure unmanaged resources are cleaned up */
>>     if (hibr_file_path)
>>       grub_free (hibr_file_path);
> grub_free already checks for not-NULL pointers.
>>     if (hibr_file)
>>       grub_file_close (hibr_file);
>>
>>     return status;
> You can eliminate status and the need of keeping one by using return
> grub_errno;
I was unaware 'grub_errno' was used so extensively.  Thanks for the tip: 
it definitely makes the logic cleaner.
>> }
>

I've followed all your recommendations (as far as possible).  Here's the 
code again.

~Peter Lustig