4.13 sdds::Reader page reading

• name:
  Reader::next, Reader::readAll
• description:
  Decode the next page with optional field projection and row slicing, or materialize every remaining page. Trailing-row selection uses bounded storage when the page row count is not known in advance.
• synopsis:
  std::optional<sdds::Page> next(sdds::ReadRequest request = {});  
  sdds::MaterializedDataset readAll(sdds::ReadRequest request = {});

• arguments:
  • request — Independent parameter, array, column, and row selection. The default loads the complete page.
• return value:
  next returns the next page or an empty optional at end of input. readAll returns the complete layout and all remaining pages.
• exceptions:
  sdds::IoError, sdds::FormatError, sdds::StateError, or sdds::LimitError, with page, field, row, and byte-offset context when available. Malformed content is fatal unless recovery was enabled and the failure is a recoverably truncated final page.
• see also:
  Sections 4.6, 4.14, and 4.15.