Refactor GetTxid() into UpdateTxid() to match coding style of hash me…

…mber variable.

UpdateTxid() is called alongside UpdateHash() when a CTransaction is
deserialized or constructed.  GetTxid() now returns a const reference.

src/primitives/transaction.cpp

@@ -132,6 +132,7 @@ CTransaction::CTransaction(const CMutableTransaction &tx) : nVersion(tx.nVersion
                                                            joinSplitPubKey(tx.joinSplitPubKey), joinSplitSig(tx.joinSplitSig)
{
    UpdateHash();
    UpdateTxid();
}

CTransaction& CTransaction::operator=(const CTransaction &tx) {
@@ -143,6 +144,7 @@ CTransaction& CTransaction::operator=(const CTransaction &tx) {
    *const_cast<uint256*>(&joinSplitPubKey) = tx.joinSplitPubKey;
    *const_cast<joinsplit_sig_t*>(&joinSplitSig) = tx.joinSplitSig;
    *const_cast<uint256*>(&hash) = tx.hash;
    *const_cast<uint256*>(&txid) = tx.txid;
    return *this;
}

@@ -227,7 +229,7 @@ std::string CTransaction::ToString() const

// Return a txid which is non-malleable.
// Signature data is cleared before the transaction is serialized and hashed.
uint256 CTransaction::GetTxid() const
void CTransaction::UpdateTxid() const
{
    // Create a deep copy of this transaction
    CMutableTransaction tx(*this);
@@ -241,10 +243,9 @@ uint256 CTransaction::GetTxid() const
    tx.joinSplitSig.assign(0);

    // Return double SHA256 hash
    return tx.GetSerializeHash();
    *const_cast<uint256*>(&txid) = tx.GetSerializeHash();
}


// Return a txid which is non-malleable.
uint256 CMutableTransaction::GetTxid() const
{

src/primitives/transaction.h

@@ -288,6 +288,8 @@ class CTransaction
    /** Memory only. */
    const uint256 hash;
    void UpdateHash() const;
    uint256 txid;
    void UpdateTxid() const;

public:
    typedef boost::array<unsigned char, 64> joinsplit_sig_t;
@@ -331,8 +333,10 @@ class CTransaction
                READWRITE(*const_cast<joinsplit_sig_t*>(&joinSplitSig));
            }
        }
        if (ser_action.ForRead())
        if (ser_action.ForRead()) {
            UpdateHash();
            UpdateTxid();
        }
    }

    bool IsNull() const {
@@ -374,9 +378,10 @@ class CTransaction

    std::string ToString() const;

    // Return the txid which is the double SHA256 hash of the transaction.
    uint256 GetTxid() const;

    // Return the txid, which is the double SHA256 hash over portions of the transaction.
    const uint256& GetTxid() const {
        return txid;
    }
};

/** A mutable version of CTransaction. */