Feature Request: Auto Casting C-types

[byehack]

In continue of #2 (comment)

All functions are typed for both arguments and results. but current behavior is, it'll raise if our entered arguments types are not exact same as specified.

proposed behavior is that it should auto casting the types for both arguments and results.

here is current working script:

from Windows.Win32.System.Rpc import RpcStringBindingComposeW
from Windows import UInt16, c_wchar_p
from ctypes import POINTER, cast

strBinding = cast(c_wchar_p(), POINTER(UInt16))
rStatus = RpcStringBindingComposeW(
    cast(c_wchar_p("0767a036-0d22-48aa-ba69-b619480f38cb"), POINTER(UInt16)),
    cast(c_wchar_p("ncalrpc"), POINTER(UInt16)),
    None,
    None,
    None,
    strBinding)
strBinding = cast(strBinding, c_wchar_p)

print(rStatus, strBinding.value)

Auto Casting will remove cast from our side:

from Windows.Win32.System.Rpc import RpcStringBindingComposeW
from Windows import UInt16, c_wchar_p

strBinding = c_wchar_p()
rStatus = RpcStringBindingComposeW(
    c_wchar_p("0767a036-0d22-48aa-ba69-b619480f38cb"),
    c_wchar_p("ncalrpc"),
    None,
    None,
    None,
    strBinding)
print(rStatus, strBinding.value)

[byehack]

Auto Casting will remove cast from our side:

from Windows.Win32.System.Rpc import RpcStringBindingComposeW
from Windows import UInt16, c_wchar_p

strBinding = c_wchar_p()
rStatus = RpcStringBindingComposeW(
    c_wchar_p("0767a036-0d22-48aa-ba69-b619480f38cb"),
    c_wchar_p("ncalrpc"),
    None,
    None,
    None,
    strBinding)
print(rStatus, strBinding.value)

And if we assume string object type is c_wchar_p and byte object type is c_char_p, we can have even simpler call:

from Windows.Win32.System.Rpc import RpcStringBindingComposeW
from Windows import c_wchar_p

strBinding = c_wchar_p()
rStatus = RpcStringBindingComposeW("0767a036-0d22-48aa-ba69-b619480f38cb", "ncalrpc", None, None, None, strBinding)
print(rStatus, strBinding.value)

I think this is current behavior in ctypes module when we are calling a typed function.

[ynkdir]

WIP
I have not confirmed yet that if getting pointer value with byref(c_wchar_p()) is safe.

[ynkdir]

It seems to work.
I merged fix.
Could you confirm that works for you.

[byehack]

That's great, I can confirm both WIP examples above have been tested and passed successfully,

[byehack]

Reopened bcz still need to work to be complete. Look at this example (you can try to repro):

currently working script:

from Windows.Win32.System.Rpc import RPC_SECURITY_QOS_V3_W
from Windows.Win32.Security import CreateWellKnownSid, WELL_KNOWN_SID_TYPE_WinLocalSystemSid
from ctypes import cast, c_ulong, c_void_p, create_string_buffer

SECURITY_MAX_SID_SIZE = 68
sidSize = c_ulong(SECURITY_MAX_SID_SIZE)
sid = create_string_buffer(SECURITY_MAX_SID_SIZE)
rStatus = CreateWellKnownSid(
    WELL_KNOWN_SID_TYPE_WinLocalSystemSid,
    None,
    sid,
    sidSize)
if not rStatus:
    raise
security = RPC_SECURITY_QOS_V3_W()
security.Sid = cast(sid, c_void_p)

Expected Work with auto casting:

from Windows.Win32.System.Rpc import RPC_SECURITY_QOS_V3_W
from Windows.Win32.Security import CreateWellKnownSid, WELL_KNOWN_SID_TYPE_WinLocalSystemSid
from ctypes import cast, c_ulong, c_void_p, create_string_buffer

SECURITY_MAX_SID_SIZE = 68
sidSize = SECURITY_MAX_SID_SIZE # removed c_ulong
sid = create_string_buffer(SECURITY_MAX_SID_SIZE)
rStatus = CreateWellKnownSid(
    WELL_KNOWN_SID_TYPE_WinLocalSystemSid,
    None,
    sid,
    sidSize) # not work after removed c_ulong
if not rStatus:
    raise
security = RPC_SECURITY_QOS_V3_W()
security.Sid = sid # not work after removed cast

[byehack]

^^^ This PR still not able to to cover removed cast(sid, c_void_p)

[byehack]

In continue of #8 I decided to create a TODO list to improve auto casting:

• Parameters Pointers
• Parameters Unions
• Other types of Parameters
• Results Pointers
• Results Unions
• Other types of Results

[byehack]

py-win32more/Windows/__init__.py

Lines 65 to 74 in c723275

	def easycast(obj, type_):
	if isinstance(obj, str):
	if issubclass(type_, (POINTER(Int16), POINTER(UInt16))):
	return cast(c_wchar_p(obj), type_)
	elif isinstance(obj, c_wchar_p):
	if issubclass(type_, (POINTER(Int16), POINTER(UInt16))):
	return cast(obj, type_)
	elif issubclass(type_, (POINTER(POINTER(Int16)), POINTER(POINTER(UInt16)))):
	return cast(pointer(obj), type_)
	return obj

the function name is easycast but it has 2 more different abilities:

1. it's convert related types in python object to c-type object: c_wchar_p(obj) at line 68.
2. second is pointer(obj) at line 73.

I think these 2 should break into separate functions. if I had time, I'll send a PR for these.

[ynkdir]

sidSize) # not work after removed c_ulong

For POINTER(c_int) type, it is ambiguous that int should be converted as cast(123, POINTER(c_int)) or pointer(c_int(123)).
I guess it is better to keep as is for now.

[mominshaikhdevs]

what's the latest update on this?

[ynkdir]

I am still not sure how it should be.