fix MP of uint128 (doublecheck)

Author: fcarreiro

barretenberg/cpp/src/barretenberg/serialize/msgpack.hpp

@@ -150,8 +150,11 @@ inline constexpr std::string camel_case(std::string_view name)
 } // namespace msgpack_detail
 
 // Same as MSGPACK_FIELDS but expecting the serialized names to be in camelCase.
+// NOTE: We create an intermediate variable because `pack_fn` requires lvalues, and since `camel_case` returns a
+// std::string things get weird.
 #define MSGPACK_CAMEL_CASE_FIELDS(...)                                                                                 \
     void msgpack(auto pack_fn)                                                                                         \
     {                                                                                                                  \
-        pack_fn(NVPFG(::msgpack_detail::camel_case, , __VA_ARGS__));                                                   \
+        auto args = std::make_tuple(NVPFG(::msgpack_detail::camel_case, , __VA_ARGS__));                               \
+        std::apply(pack_fn, args);                                                                                     \
     }

barretenberg/cpp/src/barretenberg/serialize/msgpack_impl/uint_128_t_adaptor.hpp

@@ -7,6 +7,17 @@
 
 namespace msgpack::adaptor {
 
+// Pack function for uint128_t
+template <> struct pack<uint128_t> {
+    template <typename Stream> msgpack::packer<Stream>& operator()(msgpack::packer<Stream>& o, uint128_t const& v) const
+    {
+        // Use the bin format for 16 bytes of data
+        o.pack_bin(16);
+        o.pack_bin_body(reinterpret_cast<const char*>(&v), 16);
+        return o;
+    }
+};
+
 template <> struct convert<uint128_t> {
     msgpack::object const& operator()(msgpack::object const& o, uint128_t& v) const
     {

barretenberg/cpp/src/barretenberg/vm2/common/aztec_types.hpp

@@ -6,6 +6,7 @@
 
 #include "barretenberg/common/streams.hpp" // Derives operator<< from MSGPACK_FIELDS.
 #include "barretenberg/serialize/msgpack.hpp"
+#include "barretenberg/serialize/msgpack_impl/uint_128_t_adaptor.hpp"
 #include "barretenberg/vm2/common/aztec_constants.hpp"
 #include "barretenberg/vm2/common/field.hpp"
 #include "msgpack/adaptor/define_decl.hpp"