Cache witness hash in CTransaction

src/primitives/transaction.cpp

@@ -67,18 +67,18 @@ uint256 CTransaction::ComputeHash() const
     return SerializeHash(*this, SER_GETHASH, SERIALIZE_TRANSACTION_NO_WITNESS);
 }
 
-uint256 CTransaction::GetWitnessHash() const
+uint256 CTransaction::ComputeWitnessHash() const
 {
     if (!HasWitness()) {
-        return GetHash();
+        return hash;
     }
     return SerializeHash(*this, SER_GETHASH, 0);
 }
 
 /* For backward compatibility, the hash is initialized to 0. TODO: remove the need for this default constructor entirely. */
-CTransaction::CTransaction() : vin(), vout(), nVersion(CTransaction::CURRENT_VERSION), nLockTime(0), hash() {}
-CTransaction::CTransaction(const CMutableTransaction &tx) : vin(tx.vin), vout(tx.vout), nVersion(tx.nVersion), nLockTime(tx.nLockTime), hash(ComputeHash()) {}
-CTransaction::CTransaction(CMutableTransaction &&tx) : vin(std::move(tx.vin)), vout(std::move(tx.vout)), nVersion(tx.nVersion), nLockTime(tx.nLockTime), hash(ComputeHash()) {}
+CTransaction::CTransaction() : vin(), vout(), nVersion(CTransaction::CURRENT_VERSION), nLockTime(0), hash{}, m_witness_hash{} {}
+CTransaction::CTransaction(const CMutableTransaction& tx) : vin(tx.vin), vout(tx.vout), nVersion(tx.nVersion), nLockTime(tx.nLockTime), hash{ComputeHash()}, m_witness_hash{ComputeWitnessHash()} {}
+CTransaction::CTransaction(CMutableTransaction&& tx) : vin(std::move(tx.vin)), vout(std::move(tx.vout)), nVersion(tx.nVersion), nLockTime(tx.nLockTime), hash{ComputeHash()}, m_witness_hash{ComputeWitnessHash()} {}
 
 CAmount CTransaction::GetValueOut() const
 {

src/primitives/transaction.h

@@ -286,8 +286,10 @@ public:
 private:
     /** Memory only. */
     const uint256 hash;
+    const uint256 m_witness_hash;
 
     uint256 ComputeHash() const;
+    uint256 ComputeWitnessHash() const;
 
 public:
     /** Construct a CTransaction that qualifies as IsNull() */
@@ -311,12 +313,8 @@ public:
         return vin.empty() && vout.empty();
     }
 
-    const uint256& GetHash() const {
-        return hash;
-    }
-
-    // Compute a hash that includes both transaction and witness data
-    uint256 GetWitnessHash() const;
+    const uint256& GetHash() const { return hash; }
+    const uint256& GetWitnessHash() const { return m_witness_hash; };
 
     // Return sum of txouts.
     CAmount GetValueOut() const;