code: func NewRawV4EventReader(src io.Reader, srcName string) EventReader {
  	buf := make([]byte, sizeOfBasicV4EventHeader, sizeOfBasicV4EventHeader)
  	return &rawV4EventReader{
  		src:             src,
  		srcName:         srcName,
  		logPosition:     0,
  		rawHeaderBuffer: buf,
  		isClosed:        false,
  		headerBuffer:    nil,
  		bodyBuffer:      nil,
  		nextEvent:       nil,
  	}
  }
docs: // This returns an EventReader which extracts entries from the src event stream
  // and returns the entries as RawV4Event objects.  The src stream can be a
  // binary log event stream or a relay log event stream.  NOTE: This reader
  // assumes there is no binlog magic marker at the beginning of the stream.
  // It also assumes the event entries are serialized using v4 binlog format.
  // Finally, this reader does not set sizes for extra headers, fixed length data,
  // and checksum (i.e. event.VariableLengthData() will return the entire event
  // payload).