Merge #12731: Support serialization as another type without casting

818dc74 Support serialization as another type without casting (Pieter Wuille)

Pull request description:

  This adds a `READWRITEAS(type, obj)` macro which serializes `obj` as if it were converted to `const type&` when `const`, and to `type&` when non-`const`. No actual cast is involved, so this only works when this conversion can be done automatically.

  This makes it usable in serialization code that uses a single implementation for both serialization and deserializing, which doesn't know the constness of the object involved.

  This is a redo of #12712, using a slightly different interface.

Tree-SHA512: 262f0257284ff99b5ffaec9b997c194e221522ba35c3ac8eaa9bb344449d7ea0a314de254dc77449fa7aaa600f8cd9a24da65aade8c1ec6aa80c6e9a7bba5ca7

1 files changed, 6 insertions, 1 deletions

diff --git a/src/serialize.h b/src/serialize.h
index e90b041cc2..57e434faf1 100644
--- a/src/serialize.h
+++ b/src/serialize.h
@@ -155,7 +155,12 @@ enum
     SER_GETHASH         = (1 << 2),
 };
 
-#define READWRITE(...)      (::SerReadWriteMany(s, ser_action, __VA_ARGS__))
+//! Convert the reference base type to X, without changing constness or reference type.
+template<typename X> X& ReadWriteAsHelper(X& x) { return x; }
+template<typename X> const X& ReadWriteAsHelper(const X& x) { return x; }
+
+#define READWRITE(...) (::SerReadWriteMany(s, ser_action, __VA_ARGS__))
+#define READWRITEAS(type, obj) (::SerReadWriteMany(s, ser_action, ReadWriteAsHelper<type>(obj)))
 
 /** 
  * Implement three methods for serializable objects. These are actually wrappers over