Switch CCoinsView and chainstate db from per-txid to per-txout

This patch makes several related changes:
* Changes the CCoinsView virtual methods (GetCoins, HaveCoins, ...)
  to be COutPoint/Coin-based rather than txid/CCoins-based.
* Changes the chainstate db to a new incompatible format that is also
  COutPoint/Coin based.
* Implements reconstruction code for hash_serialized_2.
* Adapts the coins_tests unit tests (thanks to Russell Yanofsky).

A side effect of the new CCoinsView model is that we can no longer
use the (unreliable) test for transaction outputs in the UTXO set
to determine whether we already have a particular transaction.

1 files changed, 27 insertions, 6 deletions

diff --git a/src/txmempool.h b/src/txmempool.h
index 6547f64f74..c86859118a 100644
--- a/src/txmempool.h
+++ b/src/txmempool.h
@@ -30,8 +30,8 @@
 class CAutoFile;
 class CBlockIndex;
 
-/** Fake height value used in CCoins to signify they are only in the memory pool (since 0.8) */
-static const unsigned int MEMPOOL_HEIGHT = 0x7FFFFFFF;
+/** Fake height value used in Coin to signify they are only in the memory pool (since 0.8) */
+static const uint32_t MEMPOOL_HEIGHT = 0x7FFFFFFF;
 
 struct LockPoints
 {
@@ -321,6 +321,20 @@ enum class MemPoolRemovalReason {
     REPLACED     //! Removed for replacement
 };
 
+class SaltedTxidHasher
+{
+private:
+    /** Salt */
+    const uint64_t k0, k1;
+
+public:
+    SaltedTxidHasher();
+
+    size_t operator()(const uint256& txid) const {
+        return SipHashUint256(k0, k1, txid);
+    }
+};
+
 /**
  * CTxMemPool stores valid-according-to-the-current-best-chain transactions
  * that may be included in the next block.
@@ -570,10 +584,10 @@ public:
     CFeeRate GetMinFee(size_t sizelimit) const;
 
     /** Remove transactions from the mempool until its dynamic size is <= sizelimit.
-      *  pvNoSpendsRemaining, if set, will be populated with the list of transactions
+      *  pvNoSpendsRemaining, if set, will be populated with the list of outpoints
       *  which are not in mempool which no longer have any spends in this mempool.
       */
-    void TrimToSize(size_t sizelimit, std::vector<uint256>* pvNoSpendsRemaining=NULL);
+    void TrimToSize(size_t sizelimit, std::vector<COutPoint>* pvNoSpendsRemaining=NULL);
 
     /** Expire all transaction (and their dependencies) in the mempool older than time. Return the number of removed transactions. */
     int Expire(int64_t time);
@@ -599,6 +613,13 @@ public:
         return (mapTx.count(hash) != 0);
     }
 
+    bool exists(const COutPoint& outpoint) const
+    {
+        LOCK(cs);
+        auto it = mapTx.find(outpoint.hash);
+        return (it != mapTx.end() && outpoint.n < it->GetTx().vout.size());
+    }
+
     CTransactionRef get(const uint256& hash) const;
     TxMempoolInfo info(const uint256& hash) const;
     std::vector<TxMempoolInfo> infoAll() const;
@@ -658,8 +679,8 @@ protected:
 
 public:
     CCoinsViewMemPool(CCoinsView* baseIn, const CTxMemPool& mempoolIn);
-    bool GetCoins(const uint256 &txid, CCoins &coins) const;
-    bool HaveCoins(const uint256 &txid) const;
+    bool GetCoins(const COutPoint &outpoint, Coin &coin) const;
+    bool HaveCoins(const COutPoint &outpoint) const;
 };
 
 #endif // BITCOIN_TXMEMPOOL_H