Make CTransaction actually immutable

2 files changed, 87 insertions, 90 deletions

diff --git a/src/primitives/transaction.cpp b/src/primitives/transaction.cpp
index 91f4d29488..11d7eace55 100644
--- a/src/primitives/transaction.cpp
+++ b/src/primitives/transaction.cpp
@@ -62,9 +62,9 @@ uint256 CMutableTransaction::GetHash() const
     return SerializeHash(*this, SER_GETHASH, SERIALIZE_TRANSACTION_NO_WITNESS);
 }
 
-void CTransaction::UpdateHash() const
+uint256 CTransaction::ComputeHash() const
 {
-    *const_cast<uint256*>(&hash) = SerializeHash(*this, SER_GETHASH, SERIALIZE_TRANSACTION_NO_WITNESS);
+    return SerializeHash(*this, SER_GETHASH, SERIALIZE_TRANSACTION_NO_WITNESS);
 }
 
 uint256 CTransaction::GetWitnessHash() const
@@ -72,25 +72,10 @@ uint256 CTransaction::GetWitnessHash() const
     return SerializeHash(*this, SER_GETHASH, 0);
 }
 
-CTransaction::CTransaction() : nVersion(CTransaction::CURRENT_VERSION), vin(), vout(), nLockTime(0) { }
-
-CTransaction::CTransaction(const CMutableTransaction &tx) : nVersion(tx.nVersion), vin(tx.vin), vout(tx.vout), wit(tx.wit), nLockTime(tx.nLockTime) {
-    UpdateHash();
-}
-
-CTransaction::CTransaction(CMutableTransaction &&tx) : nVersion(tx.nVersion), vin(std::move(tx.vin)), vout(std::move(tx.vout)), wit(std::move(tx.wit)), nLockTime(tx.nLockTime) {
-    UpdateHash();
-}
-
-CTransaction& CTransaction::operator=(const CTransaction &tx) {
-    *const_cast<int*>(&nVersion) = tx.nVersion;
-    *const_cast<std::vector<CTxIn>*>(&vin) = tx.vin;
-    *const_cast<std::vector<CTxOut>*>(&vout) = tx.vout;
-    *const_cast<CTxWitness*>(&wit) = tx.wit;
-    *const_cast<unsigned int*>(&nLockTime) = tx.nLockTime;
-    *const_cast<uint256*>(&hash) = tx.hash;
-    return *this;
-}
+/* For backward compatibility, the hash is initialized to 0. TODO: remove the need for this default constructor entirely. */
+CTransaction::CTransaction() : nVersion(CTransaction::CURRENT_VERSION), vin(), vout(), nLockTime(0), hash() {}
+CTransaction::CTransaction(const CMutableTransaction &tx) : nVersion(tx.nVersion), vin(tx.vin), vout(tx.vout), wit(tx.wit), nLockTime(tx.nLockTime), hash(ComputeHash()) {}
+CTransaction::CTransaction(CMutableTransaction &&tx) : nVersion(tx.nVersion), vin(std::move(tx.vin)), vout(std::move(tx.vout)), wit(std::move(tx.wit)), nLockTime(tx.nLockTime), hash(ComputeHash()) {}
 
 CAmount CTransaction::GetValueOut() const
 {
diff --git a/src/primitives/transaction.h b/src/primitives/transaction.h
index 0fa85a1519..66fefafef5 100644
--- a/src/primitives/transaction.h
+++ b/src/primitives/transaction.h
@@ -286,73 +286,81 @@ struct CMutableTransaction;
  *   - CTxWitness wit;
  * - uint32_t nLockTime
  */
-template<typename Stream, typename Operation, typename TxType>
-inline void SerializeTransaction(TxType& tx, Stream& s, Operation ser_action) {
+template<typename Stream, typename TxType>
+inline void UnserializeTransaction(TxType& tx, Stream& s) {
     const bool fAllowWitness = !(s.GetVersion() & SERIALIZE_TRANSACTION_NO_WITNESS);
 
-    READWRITE(*const_cast<int32_t*>(&tx.nVersion));
+    s >> tx.nVersion;
     unsigned char flags = 0;
-    if (ser_action.ForRead()) {
-        const_cast<std::vector<CTxIn>*>(&tx.vin)->clear();
-        const_cast<std::vector<CTxOut>*>(&tx.vout)->clear();
-        const_cast<CTxWitness*>(&tx.wit)->SetNull();
-        /* Try to read the vin. In case the dummy is there, this will be read as an empty vector. */
-        READWRITE(*const_cast<std::vector<CTxIn>*>(&tx.vin));
-        if (tx.vin.size() == 0 && fAllowWitness) {
-            /* We read a dummy or an empty vin. */
-            READWRITE(flags);
-            if (flags != 0) {
-                READWRITE(*const_cast<std::vector<CTxIn>*>(&tx.vin));
-                READWRITE(*const_cast<std::vector<CTxOut>*>(&tx.vout));
-            }
-        } else {
-            /* We read a non-empty vin. Assume a normal vout follows. */
-            READWRITE(*const_cast<std::vector<CTxOut>*>(&tx.vout));
-        }
-        if ((flags & 1) && fAllowWitness) {
-            /* The witness flag is present, and we support witnesses. */
-            flags ^= 1;
-            const_cast<CTxWitness*>(&tx.wit)->vtxinwit.resize(tx.vin.size());
-            READWRITE(tx.wit);
-        }
-        if (flags) {
-            /* Unknown flag in the serialization */
-            throw std::ios_base::failure("Unknown transaction optional data");
+    tx.vin.clear();
+    tx.vout.clear();
+    tx.wit.SetNull();
+    /* Try to read the vin. In case the dummy is there, this will be read as an empty vector. */
+    s >> tx.vin;
+    if (tx.vin.size() == 0 && fAllowWitness) {
+        /* We read a dummy or an empty vin. */
+        s >> flags;
+        if (flags != 0) {
+            s >> tx.vin;
+            s >> tx.vout;
         }
     } else {
-        // Consistency check
-        assert(tx.wit.vtxinwit.size() <= tx.vin.size());
-        if (fAllowWitness) {
-            /* Check whether witnesses need to be serialized. */
-            if (!tx.wit.IsNull()) {
-                flags |= 1;
-            }
-        }
-        if (flags) {
-            /* Use extended format in case witnesses are to be serialized. */
-            std::vector<CTxIn> vinDummy;
-            READWRITE(vinDummy);
-            READWRITE(flags);
+        /* We read a non-empty vin. Assume a normal vout follows. */
+        s >> tx.vout;
+    }
+    if ((flags & 1) && fAllowWitness) {
+        /* The witness flag is present, and we support witnesses. */
+        flags ^= 1;
+        tx.wit.vtxinwit.resize(tx.vin.size());
+        s >> tx.wit;
+    }
+    if (flags) {
+        /* Unknown flag in the serialization */
+        throw std::ios_base::failure("Unknown transaction optional data");
+    }
+    s >> tx.nLockTime;
+}
+
+template<typename Stream, typename TxType>
+inline void SerializeTransaction(const TxType& tx, Stream& s) {
+    const bool fAllowWitness = !(s.GetVersion() & SERIALIZE_TRANSACTION_NO_WITNESS);
+
+    s << tx.nVersion;
+    unsigned char flags = 0;
+    // Consistency check
+    assert(tx.wit.vtxinwit.size() <= tx.vin.size());
+    if (fAllowWitness) {
+        /* Check whether witnesses need to be serialized. */
+        if (!tx.wit.IsNull()) {
+            flags |= 1;
         }
-        READWRITE(*const_cast<std::vector<CTxIn>*>(&tx.vin));
-        READWRITE(*const_cast<std::vector<CTxOut>*>(&tx.vout));
-        if (flags & 1) {
-            const_cast<CTxWitness*>(&tx.wit)->vtxinwit.resize(tx.vin.size());
-            READWRITE(tx.wit);
+    }
+    if (flags) {
+        /* Use extended format in case witnesses are to be serialized. */
+        std::vector<CTxIn> vinDummy;
+        s << vinDummy;
+        s << flags;
+    }
+    s << tx.vin;
+    s << tx.vout;
+    if (flags & 1) {
+        for (size_t i = 0; i < tx.vin.size(); i++) {
+            if (i < tx.wit.vtxinwit.size()) {
+                s << tx.wit.vtxinwit[i];
+            } else {
+                s << CTxInWitness();
+            }
         }
     }
-    READWRITE(*const_cast<uint32_t*>(&tx.nLockTime));
+    s << tx.nLockTime;
 }
 
+
 /** The basic transaction that is broadcasted on the network and contained in
  * blocks.  A transaction can contain multiple inputs and outputs.
  */
 class CTransaction
 {
-private:
-    /** Memory only. */
-    const uint256 hash;
-
 public:
     // Default transaction version.
     static const int32_t CURRENT_VERSION=1;
@@ -374,6 +382,13 @@ public:
     CTxWitness wit; // Not const: can change without invalidating the txid cache
     const uint32_t nLockTime;
 
+private:
+    /** Memory only. */
+    const uint256 hash;
+
+    uint256 ComputeHash() const;
+
+public:
     /** Construct a CTransaction that qualifies as IsNull() */
     CTransaction();
 
@@ -381,18 +396,13 @@ public:
     CTransaction(const CMutableTransaction &tx);
     CTransaction(CMutableTransaction &&tx);
 
-    CTransaction& operator=(const CTransaction& tx);
-
-    ADD_SERIALIZE_METHODS;
-
-    template <typename Stream, typename Operation>
-    inline void SerializationOp(Stream& s, Operation ser_action) {
-        SerializeTransaction(*this, s, ser_action);
-        if (ser_action.ForRead()) {
-            UpdateHash();
-        }
+    template <typename Stream>
+    inline void Serialize(Stream& s) const {
+        SerializeTransaction(*this, s);
     }
 
+    /** This deserializing constructor is provided instead of an Unserialize method.
+     *  Unserialize is not possible, since it would require overwriting const fields. */
     template <typename Stream>
     CTransaction(deserialize_type, Stream& s) : CTransaction(CMutableTransaction(deserialize, s)) {}
 
@@ -417,7 +427,7 @@ public:
 
     // Compute modified tx size for priority calculation (optionally given tx size)
     unsigned int CalculateModifiedSize(unsigned int nTxSize=0) const;
-    
+
     /**
      * Get the total transaction size in bytes, including witness data.
      * "Total Size" defined in BIP141 and BIP144.
@@ -441,8 +451,6 @@ public:
     }
 
     std::string ToString() const;
-
-    void UpdateHash() const;
 };
 
 /** A mutable version of CTransaction. */
@@ -457,11 +465,15 @@ struct CMutableTransaction
     CMutableTransaction();
     CMutableTransaction(const CTransaction& tx);
 
-    ADD_SERIALIZE_METHODS;
+    template <typename Stream>
+    inline void Serialize(Stream& s) const {
+        SerializeTransaction(*this, s);
+    }
 
-    template <typename Stream, typename Operation>
-    inline void SerializationOp(Stream& s, Operation ser_action) {
-        SerializeTransaction(*this, s, ser_action);
+
+    template <typename Stream>
+    inline void Unserialize(Stream& s) {
+        UnserializeTransaction(*this, s);
     }
 
     template <typename Stream>