How can I marshall between XLOPER and VARIANT? [closed]

问题

I'm working on an Excel plugin (XLL), which communicates with COM objects. So, I have to marshall between XLOPER and VARIANT. I've got most of this working, but arrays are definitely a pain. I need to support 1- and 2D arrays.

I imagine someone has already had to deal with this before. What's the best way to simplify dealing with VARIANT, SAFEARRAY, and XLOPER (and XLOPER12)?

回答1:

I had to hand-roll my own marshalling code for this. There were no freely available libs to handle this. XLW is meant for wrapping your entire plugin - this was not an option for me.

In the end, it just took a lot of time, looking through the documentation for xloper and variant, and figuring out how to map them to each other.

For the curious:

arrays in xloper(12):

.xltype is xltypeMulti
.val.array is a pointer to an array of xlopers.

arrays in variant:

.vt is VT_ARRAY | VT_VARIANT
.parray is a SafeArray of variants

other tips with this marshalling:

xltypeRef and xltypeSRef: use xlCoerce to look up actual cell values.
integer values run the risk of overflow. boost::numeric_cast helps with that.
string marshalling is annoying. xloper uses char, xloper12 uses wchar, variant uses bstr.
Remember to free the buffers you allocate for your new xloper strings. Use xlbitDLLFree and xlAutoFree(12) accordingly.
Template programming is useful for the xloper/xloper12 issue. Boost helps. _bstr_t also helps.

回答2:

I use XLL Plus (costs) http://www.as-ltd.co.uk/xllplus/default.htm

There is also XLW (opensource) http://xlw.sourceforge.net/

and probably others I am not aware of

来源：https://stackoverflow.com/questions/4514679/how-can-i-marshall-between-xloper-and-variant

标签

c++

excel

marshalling

variant

safearray