Function parseField

fdbrpc/TokenSign.cpp:380–412

template <class FieldType>
bool parseField(Arena& arena, Optional<FieldType>& out, const rapidjson::Document& d, const char* fieldName) {
	auto fieldItr = d.FindMember(fieldName);
	if (fieldItr == d.MemberEnd())
		return true;
	auto const& field = fieldItr->value;
	static_assert(std::is_same_v<StringRef, FieldType> || std::is_same_v<FieldType, uint64_t> ||
	              std::is_same_v<FieldType, VectorRef<StringRef>>);
	if constexpr (std::is_same_v<FieldType, StringRef>) {
		if (!field.IsString())
			return false;
		out = StringRef(arena, reinterpret_cast<const uint8_t*>(field.GetString()), field.GetStringLength());
	} else if constexpr (std::is_same_v<FieldType, uint64_t>) {
		if (!field.IsNumber())
			return false;
		out = static_cast<uint64_t>(field.GetDouble());
	} else {
		if (!field.IsArray())
			return false;
		if (field.Size() > 0) {
			auto vector = new (arena) StringRef[field.Size()];
			for (auto i = 0; i < field.Size(); i++) {
				if (!field[i].IsString())
					return false;
				vector[i] = StringRef(
				    arena, reinterpret_cast<const uint8_t*>(field[i].GetString()), field[i].GetStringLength());
			}
			out = VectorRef<StringRef>(vector, field.Size());
		} else {
			out = VectorRef<StringRef>();
		}
	}
	return true;
}

bool parsePayloadPart(Arena& arena, TokenRef& token, StringRef b64urlPayload) {
	auto tmpArena = Arena();