IStream::SetSize method (objidl.h)

The SetSize method changes the size of the stream object.


  [in] ULARGE_INTEGER libNewSize


[in] libNewSize

Specifies the new size, in bytes, of the stream.

Return value

This method can return one of these values.

Return code Description
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.
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 supported by the implementation. Not all streams support greater than 232 bytes. If a stream does not support more than 232 bytes, the high DWORD data type of libNewSize must be zero. If it is nonzero, the implementation may return STG_E_INVALIDFUNCTION. In general, COM-based implementations of the IStream interface do not support streams larger than 232 bytes.
STG_E_REVERTED The object has been invalidated by a revert operation above it in the transaction tree.


IStream::SetSize changes the size of the stream object. Call this method to preallocate space for the stream. If the libNewSize parameter is 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 ISequentialStream::Write method if the seek pointer is past the current end of the stream.

If the libNewSize parameter is smaller than the current stream, 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 to obtain a large chunk of contiguous space.


Requirement Value
Minimum supported client Windows 2000 Professional [desktop apps | UWP apps]
Minimum supported server Windows 2000 Server [desktop apps | UWP apps]
Target Platform Windows
Header objidl.h
Library Uuid.lib
DLL Ole32.dll

See also



IStream - Compound File Implementation