ReleaseStgMedium (Windows Embedded CE 6.0)

1/6/2010

This function frees the specified storage medium.

Syntax

void ReleaseStgMedium( 
  STGMEDIUM* pmedium
);

Parameters

• pmedium
  [in] Pointer to the storage medium that is to be freed.

Return Value

None.

Remarks

The ReleaseStgMedium function calls the appropriate method or function to release the specified storage medium.

Use this function during data transfer operations where storage medium structures are parameters.

In addition to identifying the type of storage medium, this structure specifies the appropriate Release method for releasing the storage medium when it is no longer needed.

It is common to pass a STGMEDIUM from one body of code to another, in which the one called can allocate a medium and return it to the caller.

ReleaseStgMedium permits flexibility in whether the receiving body of code owns the medium, or whether the original provider of the medium still owns it; in which case the receiving code must inform the provider that it can free the medium.

When the original provider of the medium is responsible for freeing the medium, the provider calls ReleaseStgMedium, specifying the medium and the appropriate IUnknown pointer as the punkForRelease structure member.

Depending on the type of storage medium being freed, one of the following actions is taken, followed by a call to the Release method on the specified IUnknown pointer.

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

The provider indicates that the receiver of the medium is responsible for freeing the medium by specifying NULL for the punkForRelease structure member.

Then 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 the LocalFree function on the handle.
TYMED_GDI	Calls the Microsoft® Win32® DeleteObject function on the handle.
TYMED_ENHMF	Deletes the enhanced metafile.
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.

To determine whether the platform supports this function, see Determining Supported COM APIs.

Requirements

Header	ole2.h
Library	ole32.lib
Windows Embedded CE	Windows CE 2.10 and later

See Also

Reference

OLE Functions
Automation Functions
STGMEDIUM
IUnknown::Release
IUnknown

Concepts

Determining Supported COM APIs

Other Resources

LocalFree
DeleteObject