SAFEARRAY on linux

问题

I'm using a proprietary library on linux that uses SAFEARRAY type in a callback function:

HRESULT Write(SAFEARRAY *Data)

SAFEARRAY is defined in a header file as typedef void SAFEARRAY.

I must define a callback function that will get the data (eg. as *unsigned char) and it's length (eg. as int or size_t) and write the data somewhere.

Something like:

HRESULT MyWrite(SAFEARRAY *Data) {
  unsigned char *data = SafeArrayGetData(Data);
  size_t length = SafeArrayGetLength(Data);
  write_data_somewhere(data, length);
}

And then use it with the library:

ProprietaryLib::ExportThing(thing, MyWrite);

So my question is: How to get the data and it's length on linux, where I have no oaidl.h or oleauto.h header file.

回答1:

Two thoughts on the matter:

• Maybe you've seen it already, but Wine implements SAFEARRAY. Thus you may have a look at

  • https://github.com/wine-mirror/wine/blob/master/dlls/oleaut32/safearray.c
  • https://github.com/wine-mirror/wine/blob/master/include/oaidl.idl
  • https://github.com/wine-mirror/wine/blob/master/include/oleauto.h

• It seems to me that to get length and data of the array, it should be fine to just access the members of the struct. For instance, in safearray.c they simply read cbElements at various places, and the method SafeArrayAccessData basically only returns pvData. (In addition, it "locks" the array. The "locking" seems to be a reference counter that is checked when a SAFEARRAY is resized or freed.)

  One idea why your MYSAFEARRAY (mentioned in comments) does not work is that struct packing might interfere. In https://docs.microsoft.com/en-us/cpp/build/reference/zp-struct-member-alignment they say that Windows SDK presupposes that structs are packed on 8-byte boundaries. So perhaps you could output the raw bytes and see if you detect a pattern. If that turns out to be the problem, try to change your compiler settings.

来源：https://stackoverflow.com/questions/54345277/safearray-on-linux