IMAPISupport::IStorageFromStream

The IMAPISupport::IStorageFromStream method implements a storage object to access a stream.

Quick Info

See IMAPISupport : IUnknown.

HRESULT IStorageFromStream(
  LPUNKNOWN lpUnkIn,             
  LPCIID lpInterface,            
  ULONG ulFlags,                 
  LPSTORAGE FAR * lppStorageOut  
);
 

Parameters

lpUnkIn

[in] Pointer to a stream object.

lpInterface

[in] Pointer to the interface identifier (IID) that represents the interface to be used to access the stream pointed to by lpUnkIn. Any of the following values are valid: NULL, indicating that IStream should be used to access the stream, IID_IStream, or IID_ILockBytes.

ulFlags

[in] Bitmask of flags that controls how the storage object is to be created relative to the stream object. By default, the storage is created with read-only access and the stream starts at position zero within the storage. The following flags can be set:

STGSTRM_CREATE

A new storage object should be created for the stream object.

STGSTRM_CURRENT

The storage object should start at the current position of the stream.

STGSTRM_MODIFY

The caller should have read/write access to the returned storage object.

STGSTRM_RESET

The storage object should start at position zero.

lppStorageOut

[out] Pointer to a pointer to the storage object.

Return Values

S_OK

The storage object was successfully created.

Remarks

The IMAPISupport::IStorageFromStream method is implemented for all service provider support objects. Service providers call IStorageFromStream to create a storage object to use for opening particular properties. Service providers that have their own implementation of IStorage do not need to call IStorageFromStream.

The storage object created by IStorageFromStream calls the stream's IUnknown::AddRef method to increment its reference count and then decrements the count when the storage is released.

Notes to Callers

When the IMAPIProp::OpenProperty method of one of your objects is called to open a property with the IStorage interface, perform the following tasks:

1. Open a stream object with read/write access for the property.
2. Internally mark the property stream as a storage object.
3. Call IStorageFromStream to generate a storage object.
   1. Return a pointer to this storage object.

If you implement additional interfaces that use the storage object, create an object that wraps the storage object and implement a higher level IUnknown::QueryInterface method.

Do not allow a property to be opened with the IStream interface if it was created with IStorage. Conversely, do not allow a property to be opened with the IStorage interface if it was created with IStream.

With one exception, it is acceptable to use the IStreamDocfile interface to stream a storage object from one container to another, but the IID_IStreamDocfile interface identifier must be passed in the OpenProperty method's lpInterface parameter.

See Also

IMAPIProp::OpenProperty