func (rpc *grpcService) readFrom(request *pb.ReadRequest, reader io.ReaderAt, stream pb.ByteStream_ReadServer) error {
limit := int(request.ReadLimit)
if limit < 0 {
return grpc.Errorf(codes.InvalidArgument, "Read(): read_limit=%d is invalid", limit)
}
offset := request.ReadOffset
if offset < 0 {
return grpc.Errorf(codes.InvalidArgument, "Read(): offset=%d is invalid", offset)
}
var buf []byte
if limit > 0 {
buf = make([]byte, limit)
} else {
buf = make([]byte, 1024*1024) // 1M buffer is reasonable.
}
bytesSent := 0
for limit == 0 || bytesSent < limit {
n, err := reader.ReadAt(buf, offset)
if n > 0 {
if err := stream.Send(&pb.ReadResponse{Data: buf[:n]}); err != nil {
return grpc.Errorf(grpc.Code(err), "Send(resourceName=%q offset=%d): %v", request.ResourceName, offset, grpc.ErrorDesc(err))
}
} else if err == nil {
return grpc.Errorf(codes.Internal, "nil error on empty read: io.ReaderAt contract violated")
}
offset += int64(n)
bytesSent += n
if err == io.EOF {
break
}
if err != nil {
return grpc.Errorf(codes.Unknown, "ReadAt(resourceName=%q offset=%d): %v", request.ResourceName, offset, err)
}
}
return nil
}
// Read handles a pb.ReadRequest sending bytes to the pb.ByteStream_ReadServer
// Implements bytestream.proto "rpc Read(ReadRequest) returns (stream ReadResponse)"
func (rpc *grpcService) Read(request *pb.ReadRequest, stream pb.ByteStream_ReadServer) error {
if rpc.parent.readHandler == nil {
return grpc.Errorf(codes.Unimplemented, "instance of NewServer(readHandler = nil) rejects all reads")
}
if request == nil {
return grpc.Errorf(codes.Internal, "Read(ReadRequest == nil)")
}
if request.ResourceName == "" {
return grpc.Errorf(codes.InvalidArgument, "ReadRequest: empty or missing resource_name")
}
reader, err := rpc.parent.readHandler.GetReader(stream.Context(), request.ResourceName)
if err != nil {
return err
}
if err = rpc.readFrom(request, reader, stream); err != nil {
rpc.parent.readHandler.Close(stream.Context(), request.ResourceName)
return err
}
if err = rpc.parent.readHandler.Close(stream.Context(), request.ResourceName); err != nil {
return err
}
return nil
}