MR Michael Robellard (5314) schrieb:
> Hello,
>
> I am trying to implement the IURLSearchHook2 interface in comtypes and I
> am running into some issues.
>
> which generate the following in the comtypes.gen .py files:
> class IURLSearchHook2(IURLSearchHook):
> _case_insensitive_ = True
> _iid_ = GUID('{5EE44DA4-6D32-46E3-86BC-07540DEDD0E0}')
> _idlflags_ = []
> IURLSearchHook2._methods_ = [
> COMMETHOD([], HRESULT, 'TranslateWithSearchContext',
> ( ['in', 'out'], WSTRING, 'lpwszSearchURL' ),
> ( ['in'], c_ulong, 'cchBufferSize' ),
> ( ['in'], POINTER(ISearchContext), 'pSearchContext' )),
> ]
> I can get the data into the method and print it out fine.
> The problem is when I try and return a string out. It just plain hangs.
> If anyone has any thoughts. Is this even possible?
> I have tried both the "high level" and "low level" approach as discussed
> in Thomas' recent post
Mike, here are my thoughts on your problem.
The high level comtypes method implementation can only work for
automation-compatible
argument types, and WSTRING is not one of those.
WSTRING is defined as c_wchar_p in the generated file.
c_wchar_p is interpreted as a zero-terminated wide character string,
but what COM really passes is a buffer with space for 'cchBufferSize' wide
characters.
Which contains a zero-terminated string that you are supposed to change.
comtypes assumes c_wchar_p as 'const' strings which you cannot/should not
change.
I think you should change the 'TranslateWithSearchContext' method definition
to something like this:
> IURLSearchHook2._methods_ = [
> COMMETHOD([], HRESULT, 'TranslateWithSearchContext',
> ( ['in', 'out'], POINTER(c_wchar), 'lpwszSearchURL' ),
> ( ['in'], c_ulong, 'cchBufferSize' ),
> ( ['in'], POINTER(ISearchContext), 'pSearchContext' )),
> ]
and write the (low-level) implementation like so:
def TranslateWithSearchContext(self, this, lpwszSearchURL, cchBufferSize,
pSearchContext):
# lpwszSearchURL is a POINTER(c_wchar) instance.
rawdata = lpwszSearchURL[:cchBufferSize]
# rawdata is now a unicode string of length cchBufferSize, filled with
NUL characters
# at the end. The [in] unicode string can probably be get by this:
url = rawdata.split('\0')[0]
# Maybe ctypes.wstring_at(lpwszSearchURL) would also work.
# The [out] string must be written into the lpwszSearchURL buffer,
maybe this works:
lpwszSearchURL[:cchBufferSize] = '\0' * cchBufferSize # clear it
urlout = "http://web.somewhere.whatdoIknow";
lpwszSearchURL[:len(urlout)] = urlout
return S_OK
Thomas
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