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, 2 insertions, 2 deletions

diff --git a/src/init.cpp b/src/init.cpp
index 3bbdb16c3b..4420b6f658 100644
--- a/src/init.cpp
+++ b/src/init.cpp
@@ -146,9 +146,9 @@ class CCoinsViewErrorCatcher : public CCoinsViewBacked
 {
 public:
     CCoinsViewErrorCatcher(CCoinsView* view) : CCoinsViewBacked(view) {}
-    bool GetCoins(const uint256 &txid, CCoins &coins) const {
+    bool GetCoins(const COutPoint &outpoint, Coin &coin) const override {
         try {
-            return CCoinsViewBacked::GetCoins(txid, coins);
+            return CCoinsViewBacked::GetCoins(outpoint, coin);
         } catch(const std::runtime_error& e) {
             uiInterface.ThreadSafeMessageBox(_("Error reading from database, shutting down."), "", CClientUIInterface::MSG_ERROR);
             LogPrintf("Error reading from database: %s\n", e.what());