Keep vanetza-idf in obu-firmware, so a plain clone builds the firmware

obu-firmware builds against the vanetza-idf C-ITS library, which until now
came from the colleague's microbu-esp32c5 tree beside the repository and was
not tracked here, so a clone of this repository could not build the firmware
it ships. The library alone is now part of obu-firmware, as
obu-firmware/external/vanetza-idf: their external/vanetza-idf at commit
cf4b99f, unchanged (9775 files; see its PROVENANCE.md). CMake takes it from
there by default; -DVANETZA_IDF_DIR still points the build elsewhere.

The rest of the colleague's tree (their own VAM firmware, PKI tooling,
station-link Python tools, the V2X2MAP bridge) stays out of this repository
and gitignored; nothing is pushed to their repository. NOTES.md, docs/06,
TODO.md and the pcap verifier's usage line point at the new location.

obu-firmware/external/vanetza-idf/vanetza/geonet/lifetime.cpp

@@ -0,0 +1,102 @@
+#include "lifetime.hpp"
+#include "serialization.hpp"
+#include <vanetza/common/byte_order.hpp>
+#include <boost/units/cmath.hpp>
+#include <stdexcept>
+
+namespace vanetza
+{
+namespace geonet
+{
+
+const Lifetime Lifetime::zero()
+{
+    return Lifetime();
+}
+
+Lifetime::Lifetime()
+{
+    set(Base::Fifty_Milliseconds, 0);
+}
+
+Lifetime::Lifetime(Base base, BitNumber<uint8_t, 6> multiplier)
+{
+    set(base, multiplier);
+}
+
+void Lifetime::set(Base base, BitNumber<uint8_t, 6> multiplier)
+{
+    m_lifetime = multiplier.raw() << 2 | (static_cast<uint8_t>(base) & base_mask);
+}
+
+bool Lifetime::operator<(const Lifetime& other) const
+{
+    return this->decode() < other.decode();
+}
+
+bool Lifetime::operator==(const Lifetime& other) const
+{
+    const units::Duration diff = this->decode() - other.decode();
+    // 50 ms is the smallest non-zero value Lifetime can represent
+    const auto min_value = 0.050 * units::si::seconds;
+    return abs(diff) < min_value;
+}
+
+void Lifetime::encode(units::Duration duration)
+{
+    double seconds = duration / boost::units::si::seconds;
+    if (seconds >= 630.0) {
+        set(Base::Hundred_Seconds, std::lround(seconds / 100.0));
+    } else if (seconds >= 63.0) {
+        set(Base::Ten_Seconds, std::lround(seconds / 10.0));
+    } else if (seconds >= 3.15) {
+        set(Base::One_Second, std::lround(seconds));
+    } else {
+        set(Base::Fifty_Milliseconds, std::lround(seconds / 0.050));
+    }
+}
+
+units::Duration Lifetime::decode() const
+{
+    using vanetza::units::si::seconds;
+    Base base = static_cast<Base>(m_lifetime & base_mask);
+    const double multiplier = (m_lifetime & multiplier_mask) >> 2;
+    units::Duration unit;
+
+    switch (base) {
+        case Base::Fifty_Milliseconds:
+            unit = 0.050 * seconds;
+            break;
+        case Base::One_Second:
+            unit = 1.0 * seconds;
+            // already done
+            break;
+        case Base::Ten_Seconds:
+            unit = 10.0 * seconds;
+            break;
+        case Base::Hundred_Seconds:
+            unit = 100.0 * seconds;
+            break;
+        default:
+            throw std::runtime_error("Decoding of Lifetime::Base failed");
+            break;
+    };
+
+    return multiplier * unit;
+}
+
+void serialize(const Lifetime& lifetime, OutputArchive& ar)
+{
+    serialize(host_cast(lifetime.raw()), ar);
+}
+
+void deserialize(Lifetime& lifetime, InputArchive& ar)
+{
+    uint8_t raw;
+    deserialize(raw, ar);
+    lifetime.raw(raw);
+}
+
+} // namespace geonet
+} // namespace vanetza
+