Merge #17850: Serialization improvements (minimal initial commits)

9250a08 Convert addrdb/addrman to new serialization (Pieter Wuille)
ca33451 Introduce new serialization macros without casts (Pieter Wuille)

Pull request description:

  This is a minimal subset of #10785 that still does *something*.

  It adds a new saner serialization macro, which can be used in parallel with the old one. Then the addrdb code is converted to use this new macro.

  I'll add follow-up PRs that add more functionality + converting of other modules as things get merged.

ACKs for top commit:
  jamesob:
    ACK 9250a08 ([`jamesob/ackr/17850.1.sipa.serialization_improvemen`](https://github.com/jamesob/bitcoin/tree/ackr/17850.1.sipa.serialization_improvemen))
  kallewoof:
    ACK 9250a08
  laanwj:
    code review ACK 9250a08

Tree-SHA512: d4f58c7f85d8ada7543ee43159be57d320746abe003af11395508d280d339fac7faa198e707d1a689fb0a775fc36b3945178c3ae1c0cf9ffe685773c6ddc10c1

Author: laanwj

src/addrdb.h

@@ -49,15 +49,7 @@ class CBanEntry
         banReason = ban_reason_in;
     }
 
-    ADD_SERIALIZE_METHODS;
-
-    template <typename Stream, typename Operation>
-    inline void SerializationOp(Stream& s, Operation ser_action) {
-        READWRITE(this->nVersion);
-        READWRITE(nCreateTime);
-        READWRITE(nBanUntil);
-        READWRITE(banReason);
-    }
+    SERIALIZE_METHODS(CBanEntry, obj) { READWRITE(obj.nVersion, obj.nCreateTime, obj.nBanUntil, obj.banReason); }
 
     void SetNull()
     {

src/addrman.h

@@ -53,14 +53,10 @@ class CAddrInfo : public CAddress
 
 public:
 
-    ADD_SERIALIZE_METHODS;
-
-    template <typename Stream, typename Operation>
-    inline void SerializationOp(Stream& s, Operation ser_action) {
-        READWRITEAS(CAddress, *this);
-        READWRITE(source);
-        READWRITE(nLastSuccess);
-        READWRITE(nAttempts);
+    SERIALIZE_METHODS(CAddrInfo, obj)
+    {
+        READWRITEAS(CAddress, obj);
+        READWRITE(obj.source, obj.nLastSuccess, obj.nAttempts);
     }
 
     CAddrInfo(const CAddress &addrIn, const CNetAddr &addrSource) : CAddress(addrIn), source(addrSource)
@@ -294,7 +290,7 @@ class CAddrMan
      * This format is more complex, but significantly smaller (at most 1.5 MiB), and supports
      * changes to the ADDRMAN_ parameters without breaking the on-disk structure.
      *
-     * We don't use ADD_SERIALIZE_METHODS since the serialization and deserialization code has
+     * We don't use SERIALIZE_METHODS since the serialization and deserialization code has
      * very little in common.
      */
     template<typename Stream>

src/serialize.h

@@ -199,6 +199,30 @@ template<typename X> const X& ReadWriteAsHelper(const X& x) { return x; }
         SerializationOp(s, CSerActionUnserialize());                  \
     }
 
+/**
+ * Implement the Serialize and Unserialize methods by delegating to a single templated
+ * static method that takes the to-be-(de)serialized object as a parameter. This approach
+ * has the advantage that the constness of the object becomes a template parameter, and
+ * thus allows a single implementation that sees the object as const for serializing
+ * and non-const for deserializing, without casts.
+ */
+#define SERIALIZE_METHODS(cls, obj)                                                 \
+    template<typename Stream>                                                       \
+    void Serialize(Stream& s) const                                                 \
+    {                                                                               \
+        static_assert(std::is_same<const cls&, decltype(*this)>::value, "Serialize type mismatch"); \
+        SerializationOps(*this, s, CSerActionSerialize());                          \
+    }                                                                               \
+    template<typename Stream>                                                       \
+    void Unserialize(Stream& s)                                                     \
+    {                                                                               \
+        static_assert(std::is_same<cls&, decltype(*this)>::value, "Unserialize type mismatch"); \
+        SerializationOps(*this, s, CSerActionUnserialize());                        \
+    }                                                                               \
+    template<typename Stream, typename Type, typename Operation>                    \
+    static inline void SerializationOps(Type& obj, Stream& s, Operation ser_action) \
+
+
 #ifndef CHAR_EQUALS_INT8
 template<typename Stream> inline void Serialize(Stream& s, char a    ) { ser_writedata8(s, a); } // TODO Get rid of bare char
 #endif