IStream::SetSize

Changes the size of the stream object.

HRESULT SetSize(

ULARGE_INTEGER libNewSize

//Specifies the new size of the stream object

);

Parameter

libNewSize: [in] Specifies the new size of the stream as a number of bytes.

Return Values

S_OK: The size of the stream object was successfully changed.
E_PENDING: Asynchronous Storage only: Part or all of the stream’s data is currently unavailable. For more information see IFillLockBytes and Asynchronous Storage.
STG_E_MEDIUMFULL: The stream size is not changed because there is no space left on the storage device.
STG_E_INVALIDFUNCTION: The value of the libNewSize parameter is not valid. Since streams cannot be greater than 232 bytes in the OLE-provided implementation, the high DWORD of libNewSize must be 0. If it is nonzero, this parameter is not valid.
STG_E_REVERTED: The object has been invalidated by a revert operation above it in the transaction tree.

Remarks

IStream::SetSize changes the size of the stream object. Call this method to preallocate space for the stream. If the libNewSize parameters larger than the current stream size, the stream is extended to the indicated size by filling the intervening space with bytes of undefined value. This operation is similar to the IStream::Write method if the seek pointer is past the current end-of-stream.

If the libNewSize parameter is smaller than the current stream, then the stream is truncated to the indicated size.

The seek pointer is not affected by the change in stream size.

Calling IStream::SetSize can be an effective way of trying to obtain a large chunk of contiguous space.

ULARGE_INTEGER libNewSize	//Specifies the new size of the stream object
);