winapi - How to use DispCallFunc to call IStream::SetSize(0) in plain C -

i have stream created hglobal in winapi (in plain c, created createstreamonhglobal()). use save gpimages jpeg in memory.

i want re-use same memory stream save multiple gpimages. so, need reset stream between each call gdipsaveimagetostream().

the documentation of istream shows method ::setsize(), i'm in plain c.

i know solution winapi function dispcallfunc don't know how use , can't find documentation it.

any help? :)

you can use istream_reset example, on plain c can easy direct call interfaces methods, istream_seek macro. dispcallfunc here absolute unrelated