free function serialization DSL

Example usage for Seraphis types (in global or `sp` namespace):

```
BEGIN_SERIALIZE_OBJECT_FN(sp::SpCoinbaseEnoteCore)
    FIELD_F(onetime_address)
    VARINT_FIELD_F(amount)
END_SERIALIZE()

BEGIN_SERIALIZE_OBJECT_FN(sp::SpEnoteCore)
    FIELD_F(onetime_address)
    FIELD_F(amount_commitment)
END_SERIALIZE()
```

1 files changed, 44 insertions, 0 deletions

diff --git a/src/serialization/serialization.h b/src/serialization/serialization.h
index 2911aecb5..d1f97e324 100644
--- a/src/serialization/serialization.h
+++ b/src/serialization/serialization.h
@@ -123,6 +123,17 @@ inline bool do_serialize(Archive &ar, bool &v)
   template <bool W, template <bool> class Archive>			\
   bool member_do_serialize(Archive<W> &ar) {
 
+/*! \macro BEGIN_SERIALIZE_FN
+ *
+ * \brief Begins the environment of the DSL as a free function
+ *
+ * Inside, instead of FIELD() and VARINT_FIELD(), use FIELD_F() and
+ * VARINT_FIELD_F(). Otherwise, this macro is similar to BEGIN_SERIALIZE().
+ */
+#define BEGIN_SERIALIZE_FN(stype)                   \
+  template <bool W, template <bool> class Archive>  \
+  bool do_serialize(Archive<W> &ar, stype &v) {
+
 /*! \macro BEGIN_SERIALIZE_OBJECT
  *
  *  \brief begins the environment of the DSL
@@ -139,6 +150,27 @@ inline bool do_serialize(Archive &ar, bool &v)
   template <bool W, template <bool> class Archive>			\
   bool do_serialize_object(Archive<W> &ar){
 
+/*! \macro BEGIN_SERIALIZE_OBJECT_FN
+ *
+ * \brief Begins the environment of the DSL as a free function in object-style
+ *
+ * Inside, instead of FIELD() and VARINT_FIELD(), use FIELD_F() and
+ * VARINT_FIELD_F(). Otherwise, this macro is similar to
+ * BEGIN_SERIALIZE_OBJECT(), as you should list only field serializations.
+ */
+#define BEGIN_SERIALIZE_OBJECT_FN(stype)               \
+  template <bool W, template <bool> class Archive>     \
+  bool do_serialize_object(Archive<W> &ar, stype &v);  \
+  template <bool W, template <bool> class Archive>     \
+  bool do_serialize(Archive<W> &ar, stype &v) {        \
+    ar.begin_object();                                 \
+    bool r = do_serialize_object(ar, v);               \
+    ar.end_object();                                   \
+    return r;                                          \
+  }                                                    \
+  template <bool W, template <bool> class Archive>     \
+  bool do_serialize_object(Archive<W> &ar, stype &v) { \
+
 /*! \macro PREPARE_CUSTOM_VECTOR_SERIALIZATION
  */
 #define PREPARE_CUSTOM_VECTOR_SERIALIZATION(size, vec)			\
@@ -173,6 +205,12 @@ inline bool do_serialize(Archive &ar, bool &v)
     if (!r || !ar.good()) return false;			\
   } while(0);
 
+/*! \macro FIELD_F(f)
+ *
+ * \brief tags the field with the variable name and then serializes it (for use in a free function)
+ */
+#define FIELD_F(f) FIELD_N(#f, v.f)
+
 /*! \macro FIELDS(f)
  *
  * \brief does not add a tag to the serialized value
@@ -204,6 +242,12 @@ inline bool do_serialize(Archive &ar, bool &v)
     if (!ar.good()) return false;		\
   } while(0);
 
+/*! \macro VARINT_FIELD_F(f)
+ *
+ * \brief tags and serializes the varint \a f (for use in a free function)
+ */
+#define VARINT_FIELD_F(f) VARINT_FIELD_N(#f, v.f)
+
 /*! \macro MAGIC_FIELD(m)
  */
 #define MAGIC_FIELD(m)				\