namespace NTFSExtensions
public static class Compression
SetSparseAttribute
Mark or unmark any data stream on NTFS volume as sparse.
Signatures
public static void SetSparseAttribute(this FileInfo File, bool Sparse = true)public static void SetSparseAttribute(this FileStream File, bool Sparse = true)public static void SetSparseAttribute(SafeFileHandle FileStream, bool Sparse = true)
Parameters
this FileInfo File- A FileInfo object as a reference to file. You may call this method directly from this object, because this is an extension method.
this FileStream File- A FileStream object as a reference to opened stream. You may call this method directly from this object, because this is an extension method.
SafeFileHandle FileStream- Handle to openned stream. You can become this handle from file stream object or using WinAPI function CreateFile.
bool Sparse- Set or unset the Compressed attribute
Remarks
Using the SetSparseAttribute method you can mark or unmark any unlocked stream on NTFS volume as a sparse stream. Unlike most other attributes, the "sparse" can be changed only using a special WinAPI call.
After setting this flag you may free some regions of a stream using method SetZeroData. If the cleared region contains removable clusters, this clusters will be released, so the file will occupy less space.
Before unsetting this flag you shall fill all cleared regions. Use method RefillZeroRegions to refill all regions before unset this flag. You can unset this flag only on systems Windows Vista+. On older systems you should rewrite the stream contents to new file or stream.
Attribute changing will fail if you have not sufficient access rights or if the file is in use.
All this methods call WinAPI function, that needs a file handle. So, the most fast and safe overload is the one with SafeFileHandle.
Example
Example: working with sparse streams