IRootStorage Interface

IID_IRootStorage

{00000012-0000-0000-C000-000000000046}

The IRootStorage interface contains a single method that switches a storage object to a different underlying file and saves the storage object to that file. The save operation occurs even with low-memory conditions and uncommitted changes to the storage object. A subsequent call to IStorage::Commit is guaranteed to not consume additional memory.

The primary use for the IRootStorage interface is to save a storage object to a file during low-memory conditions. Typically, the container application calls the IRootStorage interface to switch to a new file. This interface is also useful on older systems where limits on file handles can be exceeded.

If you have an IStorage pointer to a compound file object, you can call IStorage::QueryInterface with IID_IRootStorage to obtain a pointer to the IRootStorage interface.

Methods in VTable order

IUnknown Methods

Description

QueryInterface

Returns pointers to supported interfaces.

AddRef

Increments reference count.

Release

Decrements reference count.

IRootStorage Methods

Description

SwitchToFile

Copies the file underlying this root storage object, and then associates this storage with the copied file.

QueryInterface

FUNCTION IRootStorage_QueryInterface ( _

  BYVAL pthis AS DWORD PTR _

, BYREF riid AS GUID _

, BYREF ppvObj AS DWORD _

  ) AS LONG

  LOCAL HRESULT AS LONG
  CALL DWORD @@pthis[0] USING IRootStorage_QueryInterface (pthis, riid, ppvObj) TO HRESULT
  FUNCTION = HRESULT
 

END FUNCTION

AddRef

FUNCTION IRootStorage_AddRef ( _

  BYVAL pthis AS DWORD PTR _

  ) AS DWORD
 

  LOCAL DWRESULT AS LONG
  CALL DWORD @@pthis[1] USING IRootStorage_AddRef (pthis) TO DWRESULT
  FUNCTION = DWRESULT
 

END FUNCTION

Release

FUNCTION IRootStorage_Release ( _

  BYVAL pthis AS DWORD PTR _

  ) AS DWORD
 

  LOCAL DWRESULT AS DWORD
  CALL DWORD @@pthis[2] USING IRootStorage_Release (pthis) TO DWRESULT
  FUNCTION = DWRESULT
 

END FUNCTION

SwitchToFile

FUNCTION Proto_IRootStorage_SwitchToFile ( _

  BYVAL pthis AS DWORD PTR _

, BYVAL pszFile AS DWORD _

  ) AS LONG
 

FUNCTION IRootStorage_SwitchToFile ( _

  BYVAL pthis AS DWORD PTR _

, BYVAL strFile AS STRING _

  ) AS LONG
 

  LOCAL HRESULT AS LONG

  LOCAL pszFile AS DWORD

  IF LEN(strFile) THEN
     strFile = UCODE$(strFile) & $NUL

     pszFile = STRPTR(strFile)

  END IF
  CALL DWORD @@pthis[3] USING Proto_IRootStorage_SwitchToFile (pthis, pszFile) TO HRESULT
  FUNCTION = HRESULT
 

END FUNCTION