How does VC determine that the current process is under the Administrator permission?

# Include
<
Windows. h
>

# Include
<
Stdio. h
>

Bool isadmin (
Void
);

Int
Main (
Int
Argc,
Char
*
Argv [])
{

If
(Isadmin ())
Printf (
"
Isadmin-true
"
);

Else

Printf (
"
Isadmin-false
"
);

Return
0;
}

Bool isadmin (
Void
)
{
Handle haccesstoken;
Byte
*
Infobuffer;
Ptoken_groups ptggroups;
DWORD dwinfobuffersize;
Psid psidadministrators;
Sid_identifier_authority siantauthority
=
Security_nt_authority;
Uint I;
Bool Bret
=
False;

If
(
!
Openprocesstoken (getcurrentprocess (), token_query,
&
Haccesstoken ))

Goto
Cleanup;

Infobuffer
=

New
Byte [
1024
];

If
(
!
Infobuffer)

Goto
Cleanup;

Bret
=
Gettokeninformation (haccesstoken,
Tokengroups,
Infobuffer,

1024
,

&
Dwinfobuffersize );

Closehandle (haccesstoken );

If
(
!
Bret)

Goto
Cleanup;

If
(
!
Allocateandinitializesid (
&
Siantauthority,

2
,
Security_builtin_domain_rid,
Domain_alias_rid_admins,

0
,
0
,
0
,
0
,
0
,
0
,

&
Psidadministrators ))

Goto
Cleanup;

Bret
=
False;

Ptggroups
=
(Ptoken_groups) infobuffer;

For
(I
=
0
; I
<
Ptggroups
->
Groupcount; I
++
)
{

If
(Partition Sid (psidadministrators, ptggroups
->
Groups [I]. Sid ))
{
Bret
=
True;

Break
;
}
}

Freesid (psidadministrators );

Cleanup:

If
(Infobuffer)
Delete infobuffer;

Return
Bret;
}