as_composite_access

MAYAFLUX_API std::optional< CompositeAccess > as_composite_access ( const DataVariant &  , const DataVariant &  , const DataVariant &  , const CompositeLayout &    )

friend

Validate and borrow packed Composite-compatible NDData.

Parameters

elements	DataVariant holding vector<uint8_t> packed elements.
text	DataVariant holding vector<uint8_t> UTF-8 bytes.
blob	DataVariant holding vector<uint8_t> binary bytes.
layout	Finalized layout for the packed elements.

Returns

Access view, or std::nullopt for incompatible storage or layout.

Note

This validates storage types, stride, and field extents. Individual text and binary offset bounds are checked when fields are read.

Definition at line 24 of file CompositeAccess.cpp.

{
    const auto* element_bytes = std::get_if<std::vector<uint8_t>>(&elements);
    const auto* text_bytes = std::get_if<std::vector<uint8_t>>(&text);
    const auto* blob_bytes = std::get_if<std::vector<uint8_t>>(&blob);
    const size_t stride = layout.stride_bytes();
    if (!element_bytes || !text_bytes || !blob_bytes || stride == 0
        || element_bytes->size() % stride != 0) {
        MF_WARN(Journal::Component::Kakshya, Journal::Context::Runtime,
            "as_composite_access: invalid storage or element stride");
        return std::nullopt;
    }
 
    for (const auto& field : layout.fields()) {
        if (field.offset_bytes > stride || field.size_bytes > stride - field.offset_bytes
            || ((field.type == typeid(std::string)
                    || field.type == typeid(std::vector<uint8_t>))
                && field.size_bytes != 2 * sizeof(uint64_t))
            || (field.type == typeid(detail::CompositeDynamic)
                && field.size_bytes != 3 * sizeof(uint64_t))) {
            MF_WARN(Journal::Component::Kakshya, Journal::Context::Runtime,
                "as_composite_access: invalid layout for field '{}'", field.name);
            return std::nullopt;
        }
    }
 
    return CompositeAccess(elements, text, blob, layout);
}