base support for differentiated record field accessors

src/Sessions.cc

@@ -344,8 +344,8 @@ Connection* NetSessions::FindConnection(Val* v)
 	const IPAddr& orig_addr = vl->GetFieldAs<AddrVal>(orig_h);
 	const IPAddr& resp_addr = vl->GetFieldAs<AddrVal>(resp_h);
 
-	const PortVal* orig_portv = vl->GetFieldAs<PortVal>(orig_p);
-	const PortVal* resp_portv = vl->GetFieldAs<PortVal>(resp_p);
+	auto orig_portv = vl->GetFieldAs<PortVal>(orig_p);
+	auto resp_portv = vl->GetFieldAs<PortVal>(resp_p);
 
 	ConnID id;
 

src/Val.h

@@ -73,6 +73,7 @@ class EnumVal;
 class OpaqueVal;
 class VectorVal;
 class TableEntryVal;
+class TypeVal;
 
 using AddrValPtr = IntrusivePtr<AddrVal>;
 using EnumValPtr = IntrusivePtr<EnumVal>;
@@ -446,14 +447,19 @@ public:
 	// Returns a masked port number
 	static uint32_t Mask(uint32_t port_num, TransportProto port_type);
 
-	const PortVal* Get() const	{ return AsPortVal(); }
-
 protected:
 	friend class ValManager;
 	PortVal(uint32_t p);
 
 	void ValDescribe(ODesc* d) const override;
 	ValPtr DoClone(CloneState* state) override;
+
+private:
+	// This method is just here to trick the interface in
+	// `RecordVal::GetFieldAs` into returning the right type.
+	// It shouldn't actually be used for anything.
+	friend class RecordVal;
+	PortValPtr Get()	{ return {NewRef{}, this}; }
 };
 
 class AddrVal final : public Val {
@@ -996,6 +1002,39 @@ private:
 	PDict<TableEntryVal>* table_val;
 };
 
+// This would be way easier with is_convertible_v, but sadly that won't
+// work here because Obj has deleted copy constructors (and for good
+// reason). Instead we make up our own type trait here that basically
+// combines a bunch of is_same traits into a single trait to make life
+// easier in the definitions of GetFieldAs().
+template <typename T>
+struct is_zeek_val
+	{
+	static const bool value = std::disjunction_v<
+		std::is_same<AddrVal, T>,
+		std::is_same<BoolVal, T>,
+		std::is_same<CountVal, T>,
+		std::is_same<DoubleVal, T>,
+		std::is_same<EnumVal, T>,
+		std::is_same<FileVal, T>,
+		std::is_same<FuncVal, T>,
+		std::is_same<IntVal, T>,
+		std::is_same<IntervalVal, T>,
+		std::is_same<ListVal, T>,
+		std::is_same<OpaqueVal, T>,
+		std::is_same<PatternVal, T>,
+		std::is_same<PortVal, T>,
+		std::is_same<RecordVal, T>,
+		std::is_same<StringVal, T>,
+		std::is_same<SubNetVal, T>,
+		std::is_same<TableVal, T>,
+		std::is_same<TimeVal, T>,
+		std::is_same<TypeVal, T>,
+		std::is_same<VectorVal, T>>;
+	};
+template <typename T>
+inline constexpr bool is_zeek_val_v = is_zeek_val<T>::value;
+
 class RecordVal final : public Val, public notifier::detail::Modifiable {
 public:
 	explicit RecordVal(RecordTypePtr t, bool init_fields = true);
@@ -1148,22 +1187,77 @@ public:
 
 	// The following return the given field converted to a particular
 	// underlying value.  We provide these to enable efficient
-	// access to record fields (without requiring an intermediary Val)
-	// if we change the underlying representation of records.
-	template <typename T>
-    auto GetFieldAs(int field) const -> std::invoke_result_t<decltype(&T::Get), T>
+	// access to record fields (without requiring an intermediary Val).
+	// It is up to the caller to ensure that the field exists in the
+	// record (using HasField(), if necessary).
+	template <typename T,
+	          typename std::enable_if_t<is_zeek_val_v<T>, bool> = true>
+	auto GetFieldAs(int field) const -> std::invoke_result_t<decltype(&T::Get), T>
 		{
-		auto field_ptr = GetField(field);
-		auto field_val_ptr = static_cast<T*>(field_ptr.get());
-		return field_val_ptr->Get();
+		if constexpr ( std::is_same_v<T, BoolVal> ||
+		               std::is_same_v<T, IntVal> ||
+		               std::is_same_v<T, EnumVal> )
+			return record_val->at(field).int_val;
+		else if constexpr ( std::is_same_v<T, CountVal> )
+			return record_val->at(field).uint_val;
+		else if constexpr ( std::is_same_v<T, DoubleVal> ||
+		                    std::is_same_v<T, TimeVal> ||
+		                    std::is_same_v<T, IntervalVal> )
+			return record_val->at(field).double_val;
+		else if constexpr ( std::is_same_v<T, PortVal> )
+			return val_mgr->Port(record_val->at(field).uint_val);
+		else if constexpr ( std::is_same_v<T, StringVal> )
+			return record_val->at(field).string_val->Get();
+		else if constexpr ( std::is_same_v<T, AddrVal> )
+			return record_val->at(field).addr_val->Get();
+		else if constexpr ( std::is_same_v<T, SubNetVal> )
+			return record_val->at(field).subnet_val->Get();
+		else if constexpr ( std::is_same_v<T, File> )
+			return *(record_val->at(field).file_val);
+		else if constexpr ( std::is_same_v<T, Func> )
+			return *(record_val->at(field).func_val);
+		else if constexpr ( std::is_same_v<T, PatternVal> )
+			return record_val->at(field).re_val->Get();
+		else if constexpr ( std::is_same_v<T, RecordVal> )
+			return record_val->at(field).record_val;
+		else if constexpr ( std::is_same_v<T, VectorVal> )
+			return record_val->at(field).vector_val;
+		else if constexpr ( std::is_same_v<T, TableVal> )
+			return record_val->at(field).table_val->Get();
+		else
+			{
+			// TODO: error here, although because of the
+			// type trait it really shouldn't ever get here.
+			}
+		}
+
+	template <typename T,
+	          typename std::enable_if_t<!is_zeek_val_v<T>, bool> = true>
+	T GetFieldAs(int field) const
+		{
+		if constexpr ( std::is_integral_v<T> && std::is_signed_v<T> )
+			return record_val->at(field).int_val;
+		else if constexpr ( std::is_integral_v<T> &&
+					std::is_unsigned_v<T> )
+			return record_val->at(field).uint_val;
+		else if constexpr ( std::is_floating_point_v<T> )
+			return record_val->at(field).double_val;
+
+		// Could add other types here using type traits,
+		// such as is_same_v<T, std::string>, etc.
+
+		return T{};
 		}
 
 	template <typename T>
-    auto GetFieldAs(const char* field) const -> std::invoke_result_t<decltype(&T::Get), T>
+	auto GetFieldAs(const char* field) const
 		{
-		auto field_ptr = GetField(field);
-		auto field_val_ptr = static_cast<T*>(field_ptr.get());
-		return field_val_ptr->Get();
+		int idx = GetType()->AsRecordType()->FieldOffset(field);
+
+		if ( idx < 0 )
+			reporter->InternalError("missing record field: %s", field);
+
+		return GetFieldAs<T>(idx);
 		}
 
 	void Describe(ODesc* d) const override;