Variant Streaming Code

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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

Downloads

Download source - 37 Kb


Comments

  • There may be a way to do this using VARIANT_UserMarshal, VARIANT_UserUnmarshal

    Posted by kasajian on 01/14/2010 05:14pm

    It may be possible to do this using these functions: VARIANT_UserMarshal VARIANT_UserUnmarshal

    Reply
  • The hope page for this code

    Posted by kasajian on 08/23/2007 12:31pm

    http://kasajian.com/VariantStream.html

    Reply
  • Excellent!

    Posted by Legacy on 01/09/2003 12:00am

    Originally 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
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