px schrieb:
> Thanks Thomas! This was very helpful indeed. Working great now :)
>
> Came across another problem trying to read back an unsigned byte buffer..
> I'm pretty stumped
>
> # COMMETHOD([], HRESULT, 'Read',
> # ( ['out'], POINTER(c_ubyte), 'data' ),
> # ( ['in'], c_int, 'len' ),
> # ( ['out'], POINTER(c_int), 'actual' )),
>
> When I call Read(2048), I always just get 13 back for the data field (first
> element in returned tuple) but I actually expect more bytes.
>
> I took a shot at doing a ctypes style call, but when I try to make the call
> x.Read(byref(data), len, byref(actual))
> I get
> TypeError: call takes exactly 2 arguments (4 given)
>
> It seems that comtypes only wants the in 'len' parameter.
>
>>From the IDL:
> HRESULT Read(
> [out, size_is(length), length_is(*actual)] BYTE* data,
> [in] long length,
> [out] long* actual);
comtypes isn't able to handle the 'length_is(...)' attribute. Besides,
the info from this attribute isn't present in the TLB at all. So,
you should override the generated 'Read' method in this way,
which passes the pointer as 'in' argument, and later unpacks it:
COMMETHOD([], HRESULT, 'Read',
( ['in'], POINTER(c_ubyte), 'data' ),
( ['in'], c_int, 'len' ),
( ['out'], POINTER(c_int), 'actual' )),
...]
def Read(self, len):
data = POINTER(c_ubyte)()
actual = self._Read(byref(data), len)
result = data[:actual]
# I guess you need to free the memory here?
# windll.ole32.CoTaskMemFree(data)
return result
Thomas
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