text()

std::optional< std::string_view > MayaFlux::Kakshya::Composite::text ( std::string_view  field_name ) const

noexcept

Read a present std::string field as borrowed UTF-8 bytes.

Parameters

field_name

Field to read.

Returns

Text view, or std::nullopt for an absent field, type mismatch, or invalid stored text bounds. An empty string is a present value.

Definition at line 332 of file Composite.cpp.

{
    const auto field_index = m_layout->find_field(field_name);
    if (!field_index || !has(field_name))
        return std::nullopt;
 
    const auto& field = m_layout->fields()[*field_index];
    if (field.type != typeid(std::string) && field.type != typeid(detail::CompositeDynamic))
        return std::nullopt;
 
    const auto& rows = std::get<std::vector<uint8_t>>(*m_rows);
    const auto* source = rows.data() + m_index * m_layout->stride_bytes() + field.offset_bytes;
    TextSlice slice;
    if (field.type == typeid(detail::CompositeDynamic)) {
        DynamicCell cell;
        std::memcpy(&cell, source, sizeof(cell));
        if (cell.kind != text_kind)
            return std::nullopt;
        slice = { cell.payload, cell.length };
    } else {
        std::memcpy(&slice, source, sizeof(slice));
    }
 
    const auto& text = std::get<std::vector<uint8_t>>(*m_text);
    if (slice.offset > text.size() || slice.length > text.size() - slice.offset)
        return std::nullopt;
 
    if (slice.length == 0)
        return std::string_view {};
 
    return std::string_view(
        reinterpret_cast<const char*>(text.data() + slice.offset),
        static_cast<size_t>(slice.length));
}

References MayaFlux::Kakshya::CompositeLayout::find_field(), and rows.

Referenced by MayaFlux::IO::DelimitedTextWriter::write_element().

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