ReleaseStgMedium

Frees the specified storage medium.

  • oid ReleaseStgMedium(

STGMEDIUM * pmedium
//Storage medium to be freed
);

Parameter

pmedium

Points to the storage medium that is to be freed.

Return Value

None.

Comments

The ReleaseStgMedium function frees the specified storage medium. Use this function during data transfer operations where storage medium structures are parameters, such as IDataObject::GetData or IDataObject::SetData. This structure specifies the appropriate IUnknown::Release method for releasing the storage medium when it is no longer needed.

The ReleaseStgMedium function calls the appropriate method or function to release the specified storage medium. Either the original provider of the medium or the receiver of the medium can call ReleaseStgMedium.

In cases where the original provider of the medium is responsible for freeing the medium, the provider calls ReleaseStgMedium. The ReleaseStgMedium function first makes a call as described in the following table, depending on the type of storage medium being freed.

Medium
ReleaseStgMedium Action
TYMED_HGLOBAL
None.
TYMED_GDI
None.
TYMED_ENHMF
None.
TYMED_MFPICT
None.
TYMED_FILE
Frees the filename string using standard memory management mechanisms.
TYMED_ISTREAM
Calls IStream::Release.
TYMED_ISTORAGE
Calls IStorage::Release.

After making the call described in the preceding table, ReleaseStgMedium then calls the IUnknown::Release method for the specified storage medium. This method is specified in the storage medium structure.

In cases where the receiver of the medium is responsible for freeing the medium, the storage medium structure specifies NULL for the IUnknown::Release method. In this case, the receiver calls ReleaseStgMedium, which makes a call as described in the following table depending on the type of storage medium being freed.

Medium
ReleaseStgMedium Action
TYMED_HGLOBAL
Calls GlobalFree on the handle.
TYMED_GDI
Calls DeleteObject on the handle.
TYMED_ENHMF
Deletes the enhanced metafile.
TYMED_MFPICT
The hMF that it contains is deleted with DeleteMetaFile; then the handle itself is passed to GlobalFree.
TYMED_FILE
Frees the disk file by deleting it. Frees the file name string by using the standard memory management paradigm.
TYMED_ISTREAM
Calls IStream::Release.
TYMED_ISTORAGE
Calls IStorage::Release.

In either case after the call to ReleaseStgMedium, the specified storage medium is invalid and can no longer be used.

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