Variant Streaming Code
Posted
by Kenneth Kasajian
on October 9th, 2000
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Overview
This code provides two global functions, WriteVariantToStream and ReadVariantFromStream, that enable you to read and write a variant to a stream. In addition, there are two other global functions, ReadVariantFromBlob and WriteVariantToBlob, for reading and writing a variant to a BLOB.Highlights
Here are some of the main advantages of these functions:- Uses any given IStream to stream the Variant into and out of.
- Data is streamed in efficient binary form.
- Stream is versioned for backwards compatibility.
- Supports arbitrary size and arbitrary dimension safe-arrays.
- Object streaming is supported if the object in variant supports IPersistStream[Init].
- All code is in one header file (VariantStream.h) and only two routines are exposed: WriteVariantToStream and ReadVariantFromStream.
- Comes with supporting test code that tests the header file -- in case code is modified
- Does not use C++ exception handling. Test project has EH flag turned..
- Doesn't use the CRT.
- Does not use any Direct-To-COM (VC++'s comdef.h, such as _variant_t, _bstr_t, _com_ptr, _com_error)
- Works in both Unicode and ANSI
Comments
Code moved to Github
Posted by Kenneth Kasajian on 08/08/2017 10:56pmSee Github: https://github.com/kasajian/VariantStream
ReplyThere may be a way to do this using VARIANT_UserMarshal, VARIANT_UserUnmarshal
Posted by kasajian on 01/14/2010 05:14pmIt may be possible to do this using these functions: VARIANT_UserMarshal VARIANT_UserUnmarshal
ReplyThe hope page for this code
Posted by kasajian on 08/23/2007 12:31pmhttp://kasajian.com/VariantStream.html
ReplyExcellent!
Posted by Legacy on 01/09/2003 12:00amOriginally posted by: Greg Holt
Very well thought out code. Very clean and easy to understand. I don't understand why Microsoft doesn't provide this functionality.
Only enhancement that I would like to see (and will probably end up writing it myself) is the ability to use BLOB data instead of an IStream. I know that you can use StreamToTaskMemory and BlobToStream but I don't want the overhead of having to always create a Stream everytime I want to write/read a variant.
Reply