Method Tell

r/src/io.cpp:235–256

  }

  arrow::Result<int64_t> Tell() const override {
    if (closed()) {
      return arrow::Status::IOError("R connection is closed");
    }

    // R connections use seek() with no additional arguments as a tell()
    // implementation; however, non-seekable connections will error if you
    // do this. This heuristic allows Tell() to return a reasonable value
    // (used by at least the IPC writer).
    if (!seekable_ && bytes_written_ > 0) {
      return bytes_written_;
    } else if (!seekable_) {
      return bytes_read_;
    }

    return SafeCallIntoR<int64_t>(
        [&]() {
          cpp11::sexp result = cpp11::package("base")["seek"](connection_sexp_);
          return cpp11::as_cpp<int64_t>(result);
        },
        "tell() on R connection");
  }

  bool closed() const override { return closed_; }