Generic TransactionSignatureCreator works with both CTransaction and CMutableTransaction

Templated version so that no copying of CMutableTransaction into a CTransaction is
necessary. This speeds up the test case transaction_tests/test_big_witness_transaction
from 7.9 seconds to 3.1 seconds on my machine.

4 files changed, 53 insertions, 42 deletions

diff --git a/src/script/interpreter.cpp b/src/script/interpreter.cpp
index 13f41a7cbf..4b982d647d 100644
--- a/src/script/interpreter.cpp
+++ b/src/script/interpreter.cpp
@@ -1089,9 +1089,11 @@ namespace {
  * Wrapper that serializes like CTransaction, but with the modifications
  *  required for the signature hash done in-place
  */
-class CTransactionSignatureSerializer {
+template <class T>
+class CTransactionSignatureSerializer
+{
 private:
-    const CTransaction& txTo;  //!< reference to the spending transaction (the one being serialized)
+    const T& txTo;             //!< reference to the spending transaction (the one being serialized)
     const CScript& scriptCode; //!< output script being consumed
     const unsigned int nIn;    //!< input index of txTo being signed
     const bool fAnyoneCanPay;  //!< whether the hashtype has the SIGHASH_ANYONECANPAY flag set
@@ -1099,7 +1101,7 @@ private:
     const bool fHashNone;      //!< whether the hashtype is SIGHASH_NONE
 
 public:
-    CTransactionSignatureSerializer(const CTransaction &txToIn, const CScript &scriptCodeIn, unsigned int nInIn, int nHashTypeIn) :
+    CTransactionSignatureSerializer(const T& txToIn, const CScript& scriptCodeIn, unsigned int nInIn, int nHashTypeIn) :
         txTo(txToIn), scriptCode(scriptCodeIn), nIn(nInIn),
         fAnyoneCanPay(!!(nHashTypeIn & SIGHASH_ANYONECANPAY)),
         fHashSingle((nHashTypeIn & 0x1f) == SIGHASH_SINGLE),
@@ -1180,7 +1182,9 @@ public:
     }
 };
 
-uint256 GetPrevoutHash(const CTransaction& txTo) {
+template <class T>
+uint256 GetPrevoutHash(const T& txTo)
+{
     CHashWriter ss(SER_GETHASH, 0);
     for (const auto& txin : txTo.vin) {
         ss << txin.prevout;
@@ -1188,7 +1192,9 @@ uint256 GetPrevoutHash(const CTransaction& txTo) {
     return ss.GetHash();
 }
 
-uint256 GetSequenceHash(const CTransaction& txTo) {
+template <class T>
+uint256 GetSequenceHash(const T& txTo)
+{
     CHashWriter ss(SER_GETHASH, 0);
     for (const auto& txin : txTo.vin) {
         ss << txin.nSequence;
@@ -1196,7 +1202,9 @@ uint256 GetSequenceHash(const CTransaction& txTo) {
     return ss.GetHash();
 }
 
-uint256 GetOutputsHash(const CTransaction& txTo) {
+template <class T>
+uint256 GetOutputsHash(const T& txTo)
+{
     CHashWriter ss(SER_GETHASH, 0);
     for (const auto& txout : txTo.vout) {
         ss << txout;
@@ -1206,7 +1214,8 @@ uint256 GetOutputsHash(const CTransaction& txTo) {
 
 } // namespace
 
-PrecomputedTransactionData::PrecomputedTransactionData(const CTransaction& txTo)
+template <class T>
+PrecomputedTransactionData::PrecomputedTransactionData(const T& txTo)
 {
     // Cache is calculated only for transactions with witness
     if (txTo.HasWitness()) {
@@ -1217,7 +1226,12 @@ PrecomputedTransactionData::PrecomputedTransactionData(const CTransaction& txTo)
     }
 }
 
-uint256 SignatureHash(const CScript& scriptCode, const CTransaction& txTo, unsigned int nIn, int nHashType, const CAmount& amount, SigVersion sigversion, const PrecomputedTransactionData* cache)
+// explicit instantiation
+template PrecomputedTransactionData::PrecomputedTransactionData(const CTransaction& txTo);
+template PrecomputedTransactionData::PrecomputedTransactionData(const CMutableTransaction& txTo);
+
+template <class T>
+uint256 SignatureHash(const CScript& scriptCode, const T& txTo, unsigned int nIn, int nHashType, const CAmount& amount, SigVersion sigversion, const PrecomputedTransactionData* cache)
 {
     assert(nIn < txTo.vin.size());
 
@@ -1278,7 +1292,7 @@ uint256 SignatureHash(const CScript& scriptCode, const CTransaction& txTo, unsig
     }
 
     // Wrapper to serialize only the necessary parts of the transaction being signed
-    CTransactionSignatureSerializer txTmp(txTo, scriptCode, nIn, nHashType);
+    CTransactionSignatureSerializer<T> txTmp(txTo, scriptCode, nIn, nHashType);
 
     // Serialize and hash
     CHashWriter ss(SER_GETHASH, 0);
@@ -1286,12 +1300,14 @@ uint256 SignatureHash(const CScript& scriptCode, const CTransaction& txTo, unsig
     return ss.GetHash();
 }
 
-bool TransactionSignatureChecker::VerifySignature(const std::vector<unsigned char>& vchSig, const CPubKey& pubkey, const uint256& sighash) const
+template <class T>
+bool GenericTransactionSignatureChecker<T>::VerifySignature(const std::vector<unsigned char>& vchSig, const CPubKey& pubkey, const uint256& sighash) const
 {
     return pubkey.Verify(sighash, vchSig);
 }
 
-bool TransactionSignatureChecker::CheckSig(const std::vector<unsigned char>& vchSigIn, const std::vector<unsigned char>& vchPubKey, const CScript& scriptCode, SigVersion sigversion) const
+template <class T>
+bool GenericTransactionSignatureChecker<T>::CheckSig(const std::vector<unsigned char>& vchSigIn, const std::vector<unsigned char>& vchPubKey, const CScript& scriptCode, SigVersion sigversion) const
 {
     CPubKey pubkey(vchPubKey);
     if (!pubkey.IsValid())
@@ -1312,7 +1328,8 @@ bool TransactionSignatureChecker::CheckSig(const std::vector<unsigned char>& vch
     return true;
 }
 
-bool TransactionSignatureChecker::CheckLockTime(const CScriptNum& nLockTime) const
+template <class T>
+bool GenericTransactionSignatureChecker<T>::CheckLockTime(const CScriptNum& nLockTime) const
 {
     // There are two kinds of nLockTime: lock-by-blockheight
     // and lock-by-blocktime, distinguished by whether
@@ -1348,7 +1365,8 @@ bool TransactionSignatureChecker::CheckLockTime(const CScriptNum& nLockTime) con
     return true;
 }
 
-bool TransactionSignatureChecker::CheckSequence(const CScriptNum& nSequence) const
+template <class T>
+bool GenericTransactionSignatureChecker<T>::CheckSequence(const CScriptNum& nSequence) const
 {
     // Relative lock times are supported by comparing the passed
     // in operand to the sequence number of the input.
@@ -1394,6 +1412,10 @@ bool TransactionSignatureChecker::CheckSequence(const CScriptNum& nSequence) con
     return true;
 }
 
+// explicit instantiation
+template class GenericTransactionSignatureChecker<CTransaction>;
+template class GenericTransactionSignatureChecker<CMutableTransaction>;
+
 static bool VerifyWitnessProgram(const CScriptWitness& witness, int witversion, const std::vector<unsigned char>& program, unsigned int flags, const BaseSignatureChecker& checker, ScriptError* serror)
 {
     std::vector<std::vector<unsigned char> > stack;
diff --git a/src/script/interpreter.h b/src/script/interpreter.h
index 2800473a68..2d21aa81df 100644
--- a/src/script/interpreter.h
+++ b/src/script/interpreter.h
@@ -124,7 +124,8 @@ struct PrecomputedTransactionData
     uint256 hashPrevouts, hashSequence, hashOutputs;
     bool ready = false;
 
-    explicit PrecomputedTransactionData(const CTransaction& tx);
+    template <class T>
+    explicit PrecomputedTransactionData(const T& tx);
 };
 
 enum class SigVersion
@@ -137,7 +138,8 @@ enum class SigVersion
 static constexpr size_t WITNESS_V0_SCRIPTHASH_SIZE = 32;
 static constexpr size_t WITNESS_V0_KEYHASH_SIZE = 20;
 
-uint256 SignatureHash(const CScript &scriptCode, const CTransaction& txTo, unsigned int nIn, int nHashType, const CAmount& amount, SigVersion sigversion, const PrecomputedTransactionData* cache = nullptr);
+template <class T>
+uint256 SignatureHash(const CScript& scriptCode, const T& txTo, unsigned int nIn, int nHashType, const CAmount& amount, SigVersion sigversion, const PrecomputedTransactionData* cache = nullptr);
 
 class BaseSignatureChecker
 {
@@ -160,10 +162,11 @@ public:
     virtual ~BaseSignatureChecker() {}
 };
 
-class TransactionSignatureChecker : public BaseSignatureChecker
+template <class T>
+class GenericTransactionSignatureChecker : public BaseSignatureChecker
 {
 private:
-    const CTransaction* txTo;
+    const T* txTo;
     unsigned int nIn;
     const CAmount amount;
     const PrecomputedTransactionData* txdata;
@@ -172,21 +175,15 @@ protected:
     virtual bool VerifySignature(const std::vector<unsigned char>& vchSig, const CPubKey& vchPubKey, const uint256& sighash) const;
 
 public:
-    TransactionSignatureChecker(const CTransaction* txToIn, unsigned int nInIn, const CAmount& amountIn) : txTo(txToIn), nIn(nInIn), amount(amountIn), txdata(nullptr) {}
-    TransactionSignatureChecker(const CTransaction* txToIn, unsigned int nInIn, const CAmount& amountIn, const PrecomputedTransactionData& txdataIn) : txTo(txToIn), nIn(nInIn), amount(amountIn), txdata(&txdataIn) {}
+    GenericTransactionSignatureChecker(const T* txToIn, unsigned int nInIn, const CAmount& amountIn) : txTo(txToIn), nIn(nInIn), amount(amountIn), txdata(nullptr) {}
+    GenericTransactionSignatureChecker(const T* txToIn, unsigned int nInIn, const CAmount& amountIn, const PrecomputedTransactionData& txdataIn) : txTo(txToIn), nIn(nInIn), amount(amountIn), txdata(&txdataIn) {}
     bool CheckSig(const std::vector<unsigned char>& scriptSig, const std::vector<unsigned char>& vchPubKey, const CScript& scriptCode, SigVersion sigversion) const override;
     bool CheckLockTime(const CScriptNum& nLockTime) const override;
     bool CheckSequence(const CScriptNum& nSequence) const override;
 };
 
-class MutableTransactionSignatureChecker : public TransactionSignatureChecker
-{
-private:
-    const CTransaction txTo;
-
-public:
-    MutableTransactionSignatureChecker(const CMutableTransaction* txToIn, unsigned int nInIn, const CAmount& amountIn) : TransactionSignatureChecker(&txTo, nInIn, amountIn), txTo(*txToIn) {}
-};
+using TransactionSignatureChecker = GenericTransactionSignatureChecker<CTransaction>;
+using MutableTransactionSignatureChecker = GenericTransactionSignatureChecker<CMutableTransaction>;
 
 bool EvalScript(std::vector<std::vector<unsigned char> >& stack, const CScript& script, unsigned int flags, const BaseSignatureChecker& checker, SigVersion sigversion, ScriptError* error = nullptr);
 bool VerifyScript(const CScript& scriptSig, const CScript& scriptPubKey, const CScriptWitness* witness, unsigned int flags, const BaseSignatureChecker& checker, ScriptError* serror = nullptr);
diff --git a/src/script/sign.cpp b/src/script/sign.cpp
index ac35f17f3e..c5468f633b 100644
--- a/src/script/sign.cpp
+++ b/src/script/sign.cpp
@@ -14,9 +14,9 @@
 
 typedef std::vector<unsigned char> valtype;
 
-TransactionSignatureCreator::TransactionSignatureCreator(const CTransaction* txToIn, unsigned int nInIn, const CAmount& amountIn, int nHashTypeIn) : txTo(txToIn), nIn(nInIn), nHashType(nHashTypeIn), amount(amountIn), checker(txTo, nIn, amountIn) {}
+MutableTransactionSignatureCreator::MutableTransactionSignatureCreator(const CMutableTransaction* txToIn, unsigned int nInIn, const CAmount& amountIn, int nHashTypeIn) : txTo(txToIn), nIn(nInIn), nHashType(nHashTypeIn), amount(amountIn), checker(txTo, nIn, amountIn) {}
 
-bool TransactionSignatureCreator::CreateSig(const SigningProvider& provider, std::vector<unsigned char>& vchSig, const CKeyID& address, const CScript& scriptCode, SigVersion sigversion) const
+bool MutableTransactionSignatureCreator::CreateSig(const SigningProvider& provider, std::vector<unsigned char>& vchSig, const CKeyID& address, const CScript& scriptCode, SigVersion sigversion) const
 {
     CKey key;
     if (!provider.GetKey(address, key))
@@ -209,8 +209,7 @@ bool SignSignature(const SigningProvider &provider, const CScript& fromPubKey, C
 {
     assert(nIn < txTo.vin.size());
 
-    CTransaction txToConst(txTo);
-    TransactionSignatureCreator creator(&txToConst, nIn, amount, nHashType);
+    MutableTransactionSignatureCreator creator(&txTo, nIn, amount, nHashType);
 
     SignatureData sigdata;
     bool ret = ProduceSignature(provider, creator, fromPubKey, sigdata);
diff --git a/src/script/sign.h b/src/script/sign.h
index cf3651c1de..a10366dcd1 100644
--- a/src/script/sign.h
+++ b/src/script/sign.h
@@ -37,26 +37,19 @@ public:
 };
 
 /** A signature creator for transactions. */
-class TransactionSignatureCreator : public BaseSignatureCreator {
-    const CTransaction* txTo;
+class MutableTransactionSignatureCreator : public BaseSignatureCreator {
+    const CMutableTransaction* txTo;
     unsigned int nIn;
     int nHashType;
     CAmount amount;
-    const TransactionSignatureChecker checker;
+    const MutableTransactionSignatureChecker checker;
 
 public:
-    TransactionSignatureCreator(const CTransaction* txToIn, unsigned int nInIn, const CAmount& amountIn, int nHashTypeIn=SIGHASH_ALL);
+    MutableTransactionSignatureCreator(const CMutableTransaction* txToIn, unsigned int nInIn, const CAmount& amountIn, int nHashTypeIn = SIGHASH_ALL);
     const BaseSignatureChecker& Checker() const override { return checker; }
     bool CreateSig(const SigningProvider& provider, std::vector<unsigned char>& vchSig, const CKeyID& keyid, const CScript& scriptCode, SigVersion sigversion) const override;
 };
 
-class MutableTransactionSignatureCreator : public TransactionSignatureCreator {
-    CTransaction tx;
-
-public:
-    MutableTransactionSignatureCreator(const CMutableTransaction* txToIn, unsigned int nInIn, const CAmount& amountIn, int nHashTypeIn) : TransactionSignatureCreator(&tx, nInIn, amountIn, nHashTypeIn), tx(*txToIn) {}
-};
-
 /** A signature creator that just produces 72-byte empty signatures. */
 extern const BaseSignatureCreator& DUMMY_SIGNATURE_CREATOR;