private static PB.Direction ToPBDirection(Request.GetRangeDirection direction)
        {
            switch (direction)
            {
            case Request.GetRangeDirection.Forward:
                return(PB.Direction.FORWARD);

            case Request.GetRangeDirection.Backward:
                return(PB.Direction.BACKWARD);

            default:
                throw new ArgumentException("unknown direction type:" + direction);
            }
        }
        private PB.Direction MakeDirection(Request.GetRangeDirection direction)
        {
            switch (direction)
            {
            case Request.GetRangeDirection.Forward:
                return(PB.Direction.FORWARD);

            case Request.GetRangeDirection.Backward:
                return(PB.Direction.BACKWARD);

            default:
                throw new OTSClientException(
                          String.Format("Invalid direction: {0}", direction)
                          );
            }
        }