The BetterStreams Library

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AlternateStreams

AlternateStreams enables you to read, write, delete, create and list alternate data streams (ADS) in an NTFS file.  Under NTFS, each file has a "main" unnamed stream (this is the one the Framework's file I/O classes manipulate) as well as zero or more "alternate" named streams; for example, Internet Explorer uses an alternate stream named "Zone.Identifier" to record which security zone a downloaded file came from, and in general they can be used to conveniently store arbitrary metadata for a file without the need to resort to a database or a separate metadata file.  They can also be used to create "compound storage" for application data: if your application needs to serialize ten objects to a single file, you would normally sequentially write them in XML or binary; however, to modify any of the objects, the entire file would need to be rewritten.  With alternate streams you can simply create a separate named stream for each object and modify these streams individually.  Please note that AlternateStreams requires Windows 2000/XP or later.  [examples: 1, 2]

Download an evaluation copy of the library to try it in your own applications (or use the included test package).  You can also view the documentation for this class online.

Typical applications

• Store metadata associated with a file
• Compound storage: multiple, individually modifiable streams in a single file
• Find and edit alternate data streams created by other applications

Caveats

• Alternate data streams are only available for NTFS files.  If you move a file to a FAT32 partition, all the alternate data streams will be permanently lost.
• Users may not be familiar with alternate streams (Windows Explorer doesn't include them when calculating the size of a file, for example).  Make sure to notify them if you plan to store sensitive or copious data.