Support deserializing into temporaries

Currently, the READWRITE macro cannot be passed any non-const temporaries, as
the SerReadWrite function only accepts lvalue references.

Deserializing into a temporary is very common, however. See for example
things like 's >> VARINT(n)'. The VARINT macro produces a temporary wrapper
that holds a reference to n.

Fix this by accepting non-const rvalue references instead of lvalue references.
We don't propagate the rvalue-ness down, as there are no useful optimizations
that only apply to temporaries.

Then use this new functionality to get rid of many (but not all) uses of the
'REF' macro (which casts away constness).

Author: sipa

src/blockencodings.h

@@ -90,11 +90,11 @@ class BlockTransactions {
             while (txn.size() < txn_size) {
                 txn.resize(std::min((uint64_t)(1000 + txn.size()), txn_size));
                 for (; i < txn.size(); i++)
-                    READWRITE(REF(TransactionCompressor(txn[i])));
+                    READWRITE(TransactionCompressor(txn[i]));
             }
         } else {
             for (size_t i = 0; i < txn.size(); i++)
-                READWRITE(REF(TransactionCompressor(txn[i])));
+                READWRITE(TransactionCompressor(txn[i]));
         }
     }
 };
@@ -115,7 +115,7 @@ struct PrefilledTransaction {
         if (idx > std::numeric_limits<uint16_t>::max())
             throw std::ios_base::failure("index overflowed 16-bits");
         index = idx;
-        READWRITE(REF(TransactionCompressor(tx)));
+        READWRITE(TransactionCompressor(tx));
     }
 };
 

src/coins.h

@@ -69,7 +69,7 @@ class Coin
         ::Unserialize(s, VARINT(code));
         nHeight = code >> 1;
         fCoinBase = code & 1;
-        ::Unserialize(s, REF(CTxOutCompressor(out)));
+        ::Unserialize(s, CTxOutCompressor(out));
     }
 
     bool IsSpent() const {

src/compressor.h

@@ -73,7 +73,7 @@ class CScriptCompressor
         s >> VARINT(nSize);
         if (nSize < nSpecialScripts) {
             std::vector<unsigned char> vch(GetSpecialSize(nSize), 0x00);
-            s >> REF(CFlatData(vch));
+            s >> CFlatData(vch);
             Decompress(nSize, vch);
             return;
         }
@@ -84,7 +84,7 @@ class CScriptCompressor
             s.ignore(nSize);
         } else {
             script.resize(nSize);
-            s >> REF(CFlatData(script));
+            s >> CFlatData(script);
         }
     }
 };

src/hash.h

@@ -173,7 +173,7 @@ class CHashVerifier : public CHashWriter
     }
 
     template<typename T>
-    CHashVerifier<Source>& operator>>(T& obj)
+    CHashVerifier<Source>& operator>>(T&& obj)
     {
         // Unserialize from this stream
         ::Unserialize(*this, obj);

src/script/bitcoinconsensus.cpp

@@ -40,7 +40,7 @@ class TxInputStream
     }
 
     template<typename T>
-    TxInputStream& operator>>(T& obj)
+    TxInputStream& operator>>(T&& obj)
     {
         ::Unserialize(*this, obj);
         return *this;

src/serialize.h

@@ -350,10 +350,10 @@ I ReadVarInt(Stream& is)
     }
 }
 
-#define FLATDATA(obj) REF(CFlatData((char*)&(obj), (char*)&(obj) + sizeof(obj)))
-#define VARINT(obj) REF(WrapVarInt(REF(obj)))
-#define COMPACTSIZE(obj) REF(CCompactSize(REF(obj)))
-#define LIMITED_STRING(obj,n) REF(LimitedString< n >(REF(obj)))
+#define FLATDATA(obj) CFlatData((char*)&(obj), (char*)&(obj) + sizeof(obj))
+#define VARINT(obj) WrapVarInt(REF(obj))
+#define COMPACTSIZE(obj) CCompactSize(REF(obj))
+#define LIMITED_STRING(obj,n) LimitedString< n >(REF(obj))
 
 /** 
  * Wrapper for serializing arrays and POD.
@@ -538,7 +538,7 @@ inline void Serialize(Stream& os, const T& a)
 }
 
 template<typename Stream, typename T>
-inline void Unserialize(Stream& is, T& a)
+inline void Unserialize(Stream& is, T&& a)
 {
     a.Unserialize(is);
 }
@@ -884,10 +884,10 @@ void SerializeMany(Stream& s)
 }
 
 template<typename Stream, typename Arg, typename... Args>
-void SerializeMany(Stream& s, Arg&& arg, Args&&... args)
+void SerializeMany(Stream& s, const Arg& arg, const Args&... args)
 {
-    ::Serialize(s, std::forward<Arg>(arg));
-    ::SerializeMany(s, std::forward<Args>(args)...);
+    ::Serialize(s, arg);
+    ::SerializeMany(s, args...);
 }
 
 template<typename Stream>
@@ -896,20 +896,20 @@ inline void UnserializeMany(Stream& s)
 }
 
 template<typename Stream, typename Arg, typename... Args>
-inline void UnserializeMany(Stream& s, Arg& arg, Args&... args)
+inline void UnserializeMany(Stream& s, Arg&& arg, Args&&... args)
 {
     ::Unserialize(s, arg);
     ::UnserializeMany(s, args...);
 }
 
 template<typename Stream, typename... Args>
-inline void SerReadWriteMany(Stream& s, CSerActionSerialize ser_action, Args&&... args)
+inline void SerReadWriteMany(Stream& s, CSerActionSerialize ser_action, const Args&... args)
 {
-    ::SerializeMany(s, std::forward<Args>(args)...);
+    ::SerializeMany(s, args...);
 }
 
 template<typename Stream, typename... Args>
-inline void SerReadWriteMany(Stream& s, CSerActionUnserialize ser_action, Args&... args)
+inline void SerReadWriteMany(Stream& s, CSerActionUnserialize ser_action, Args&&... args)
 {
     ::UnserializeMany(s, args...);
 }

src/streams.h

@@ -42,7 +42,7 @@ class OverrideStream
     }
 
     template<typename T>
-    OverrideStream<Stream>& operator>>(T& obj)
+    OverrideStream<Stream>& operator>>(T&& obj)
     {
         // Unserialize from this stream
         ::Unserialize(*this, obj);
@@ -399,7 +399,7 @@ class CDataStream
     }
 
     template<typename T>
-    CDataStream& operator>>(T& obj)
+    CDataStream& operator>>(T&& obj)
     {
         // Unserialize from this stream
         ::Unserialize(*this, obj);
@@ -543,7 +543,7 @@ class CAutoFile
     }
 
     template<typename T>
-    CAutoFile& operator>>(T& obj)
+    CAutoFile& operator>>(T&& obj)
     {
         // Unserialize from this stream
         if (!file)
@@ -686,7 +686,7 @@ class CBufferedFile
     }
 
     template<typename T>
-    CBufferedFile& operator>>(T& obj) {
+    CBufferedFile& operator>>(T&& obj) {
         // Unserialize from this stream
         ::Unserialize(*this, obj);
         return (*this);

src/txdb.cpp

@@ -348,7 +348,7 @@ class CCoins
         vout.assign(vAvail.size(), CTxOut());
         for (unsigned int i = 0; i < vAvail.size(); i++) {
             if (vAvail[i])
-                ::Unserialize(s, REF(CTxOutCompressor(vout[i])));
+                ::Unserialize(s, CTxOutCompressor(vout[i]));
         }
         // coinbase height
         ::Unserialize(s, VARINT(nHeight));

src/undo.h

@@ -54,7 +54,7 @@ class TxInUndoDeserializer
             int nVersionDummy;
             ::Unserialize(s, VARINT(nVersionDummy));
         }
-        ::Unserialize(s, REF(CTxOutCompressor(REF(txout->out))));
+        ::Unserialize(s, CTxOutCompressor(REF(txout->out)));
     }
 
     explicit TxInUndoDeserializer(Coin* coin) : txout(coin) {}
@@ -76,7 +76,7 @@ class CTxUndo
         uint64_t count = vprevout.size();
         ::Serialize(s, COMPACTSIZE(REF(count)));
         for (const auto& prevout : vprevout) {
-            ::Serialize(s, REF(TxInUndoSerializer(&prevout)));
+            ::Serialize(s, TxInUndoSerializer(&prevout));
         }
     }
 
@@ -90,7 +90,7 @@ class CTxUndo
         }
         vprevout.resize(count);
         for (auto& prevout : vprevout) {
-            ::Unserialize(s, REF(TxInUndoDeserializer(&prevout)));
+            ::Unserialize(s, TxInUndoDeserializer(&prevout));
         }
     }
 };