nmbs (Normalised Metadata Binding Service)

nmbs is a lightweight C++ library for generating and parsing NATO confidentiality metadata. It implements core components of the ADatP-4774 and ADatP-4778 specifications, enabling developers to consistently attach standards-compliant labels to files.

Getting Started

If installed via Debian packages (e.g., libnmbs-dev), this documentation is available locally at /usr/share/doc/libnmbs-dev/html/index.html. You can open this directly in a web browser or utilize a package such as dochelp.

The API is rooted in the nmbs namespace and is highly functional. Data structures are kept as simple, immutable structs with minimal internal logic. Most operations are performed via top-level functions (see the nmbs namespace reference).

Integration

Integrate libnmbs1 into your CMake project:

find_package(NMBS REQUIRED CONFIG)
 
target_link_libraries(Your-Target
        PRIVATE
        NMBS::NMBS-Library
)

Ensure the core header is included in your source files:

#include <nmbs/nmbs.h>

Example Usage

The following minimal example demonstrates writing and reading XMP metadata on an image.

Error handling is managed via nmbs::Expected (an alias for std::expected<T, nmbs::Error>), providing both human-readable messages and programmatic exit codes. Further examples can be found in the targets/NMBS-Examples directory of the source tree.

#include <iostream>
#include <nmbs/nmbs.h>
 
int main()
{
    const std::filesystem::path file{"my-image.jpg"};
 
    std::vector<nmbs::ConfidentialityLabel> labels(1);
    labels[0].confidentiality_information.policy_identifier = "PUBLIC";
    labels[0].confidentiality_information.classification = "UNMARKED";
 
    if (const auto output = nmbs::write_labels(file, labels); !output.has_value())
    {
        std::cerr << output.error().message() << std::endl;
        return output.error().code();
    }
 
    if (const auto result = nmbs::read_binding(file); result && *result)
    {
        for (const nmbs::binding::BindingInformation& binding = **result; const auto& label : binding.labels)
        {
            std::cout << label.confidentiality_information.policy_identifier << " " <<
                label.confidentiality_information.classification << std::endl;
        }
        return nmbs::ExitCode::success;
    }
    else if (!result)
    {
        std::cerr << result.error().message() << std::endl;
        return result.error().code();
    }
    return nmbs::ExitCode::no_label_present;
}