The following GridFS methods use stream_copy_to_stream():

• downloadToStream
• downloadToStreamByName
• uploadFromStream

These methods currently throw exceptions if the file cannot be opened or a driver exception is encountered, but they do not check that stream_copy_to_stream() succeeds.

Users may already be aware of stream IO errors since our StreamWrapper may emit an E_USER_WARNING with an internal exception message, but we would do well to throw an exception if stream_copy_to_stream() returns boolean false.