GNU MultiPrecision includes a text deserialization sublibrary. This works basically the same way as the serialization sublibrary, if not simpler.
Handling public APIs & methodtables similarly.
There's a core number scanner deferring to existing parsers (from MPF, MPQ, or MPZ subparsers), to be wrapped in a scanf replacement.
1/1 Fin for today! Tomorrow: finish with tuning!