CreateStreamOnHGlobal - OLE Programmer's Reference (ole.hlp)

CreateStreamOnHGlobal

Returns an OLE-provided implementation of the IStream interface with the stream object stored in global memory.

HRESULT CreateStreamOnHGlobal(

HGLOBAL hGlobal,	//Memory handle for the stream object
BOOL fDeleteOnRelease,	//Indicates whether to free memory when the object is released
LPSTREAM * ppstm	//Points to location for pointer to the new stream object
);

Parameters
hGlobal

Contains the memory handle allocated by the GlobalAlloc function. The handle must be allocated as moveable and nondiscardable. If the handle is to be shared between processes, it must also be allocated as shared. New handles should be allocated with a size of zero. If hGlobal is NULL, the CreateStreamOnHGlobal function internally allocates a new shared memory block of size zero.

fDeleteOnRelease

Indicates whether the underlying handle for this stream object should be automatically freed when the stream object is released.

ppstm

Points to the location where this method places a pointer to the new stream object, that is, the new IStream instance. It cannot be NULL.

Return Values
S_OK

Indicates the stream object was created successfully.

E_OUTOFMEMORY

Indicates the stream could not be created due to lack of memory.

E_INVALIDARG

Indicates invalid value for one of the parameters.

Comments
This function creates a stream object in memory using the OLE-provided implementation of the IStream interface. The returned stream object supports both reading and writing, is not transacted, and does not support locking.

The initial contents of the stream are the current contents of the memory block provided in the hGlobal parameter. If the hGlobal paramter is NULL, this function internally allocates memory.

The current contents of the memory block are undisturbed by the creation of the new stream object. Thus, you can use this function to open an existing stream in memory.

The initial size of the stream is the size of the memory handle returned by the Win32 GlobalSize function. Because of rounding, this is not necessarily the same size that was originally allocated for the handle. If the logical size of the stream is important, you should follow the call to this function with a call to the IStream::SetSize method.

See Also
CreateStreamOnHGlobal, IStream::SetSize
GlobalSize in Win32

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