Segwit light for spending coins.

Handle segwit-light properly when spending coins, either for staking
or normal transactions in the wallet.  Depending on when a transaction
was confirmed, we need to make sure to include the right outpoint (with
txid or bare txid) in the transaction spending an output.  This is done
through a custom UTXO hasher used in the wallet, which specifically
works for CWalletTx.

Author: domob1812

divi/src/StakableCoin.h

@@ -1,10 +1,10 @@
 #ifndef STAKABLE_COIN_H
 #define STAKABLE_COIN_H
+#include <merkletx.h>
 #include <uint256.h>
-#include <primitives/transaction.h>
 struct StakableCoin
 {
-    const CTransaction* tx;
+    const CMerkleTx* tx;
     unsigned outputIndex;
     uint256 blockHashOfFirstConfirmation;
     COutPoint utxo;
@@ -18,7 +18,7 @@ struct StakableCoin
     }
 
     StakableCoin(
-        const CTransaction* txIn,
+        const CMerkleTx* txIn,
         unsigned outputIndexIn,
         uint256 blockHashIn
         ): tx(txIn)
@@ -32,4 +32,4 @@ struct StakableCoin
         return utxo < other.utxo;
     }
 };
-#endif//STAKABLE_COIN_H
+#endif//STAKABLE_COIN_H

divi/src/kernel.cpp

@@ -254,7 +254,7 @@ bool CheckProofOfStakeContextAndRecoverStakingData(
     uint256 hashBlock;
     CTransaction txPrev;
     if (!GetTransaction(txin.prevout.hash, txPrev, hashBlock, true))
-        return error("CheckProofOfStake() : INFO: read txPrev failed");
+        return error("CheckProofOfStake() : INFO: read txPrev failed for %s", txin.prevout.hash.GetHex());
 
     const CScript &kernelScript = txPrev.vout[txin.prevout.n].scriptPubKey;
 

divi/src/merkletx.h

@@ -57,4 +57,4 @@ class CMerkleTx : public CTransaction
     bool AcceptToMemoryPool(bool fLimitFree);
     bool IsTransactionLockTimedOut() const;
 };
-#endif// MERKLE_TX_H
+#endif// MERKLE_TX_H

divi/src/primitives/transaction.h

@@ -137,6 +137,8 @@ class CTransaction
 
     CTransaction& operator=(const CTransaction& tx);
 
+    virtual ~CTransaction() = default;
+
     ADD_SERIALIZE_METHODS;
 
     template <typename Stream, typename Operation>

divi/src/wallet.cpp

@@ -180,28 +180,52 @@ bool WriteTxToDisk(const CWallet* walletPtr, const CWalletTx& transactionToWrite
 namespace
 {
 
-/** Dummy UTXO hasher for the wallet.  For now, this just always returns
- *  the normal txid, but we will later change it to return the proper hash
- *  for a WalletTx.  */
+/** UTXO hasher for wallet transactions.  It uses the transaction's known block
+ *  hash (from CMerkleTx) to determine the activation state of segwit light.  */
 class WalletUtxoHasher : public TransactionUtxoHasher
 {
 
+private:
+
+  const CChain& chainActive_;
+
 public:
 
+  WalletUtxoHasher(const CChain& chain)
+    : chainActive_(chain)
+  {}
+
   uint256 GetUtxoHash(const CTransaction& tx) const override
   {
-    return tx.GetHash();
+    const CMerkleTx* mtx = dynamic_cast<const CMerkleTx*>(&tx);
+    assert(mtx != nullptr);
+
+    const CBlockIndex* pindexBlock = nullptr;
+    const int depth = mtx->GetNumberOfBlockConfirmations(pindexBlock);
+
+    /* If the transaction is not yet confirmed in a block, we use the current
+       tip to determine the segwit-light activation status.  This is not
+       perfect around the activation time, but there is nothing we can do
+       in that case anyway.  Mempool and wallet discourage spending unconfirmed
+       outputs around the segwit-light fork anyway.  */
+    if (depth <= 0)
+        pindexBlock = chainActive_.Tip();
+
+    assert(pindexBlock != nullptr);
+    const ActivationState as(pindexBlock);
+
+    return as.IsActive(Fork::SegwitLight) ? mtx->GetBareTxid() : mtx->GetHash();
   }
 
 };
 
-} // anonymous namespace
+}
 
 CWallet::CWallet(const CChain& chain, const BlockMap& blockMap
     ): cs_wallet()
     , transactionRecord_(new WalletTransactionRecord(cs_wallet,strWalletFile) )
     , outputTracker_( new SpentOutputTracker(*transactionRecord_) )
-    , utxoHasher(new WalletUtxoHasher() )
+    , utxoHasher(new WalletUtxoHasher(chain) )
     , chainActive_(chain)
     , mapBlockIndex_(blockMap)
     , orderedTransactionIndex()