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.

2 files changed, 30 insertions, 24 deletions

diff --git a/src/rpc/blockchain.cpp b/src/rpc/blockchain.cpp
index 3e9b1a1b12..77f1dcb21f 100644
--- a/src/rpc/blockchain.cpp
+++ b/src/rpc/blockchain.cpp
@@ -816,24 +816,27 @@ static bool GetUTXOStats(CCoinsView *view, CCoinsStats &stats)
         stats.nHeight = mapBlockIndex.find(stats.hashBlock)->second->nHeight;
     }
     ss << stats.hashBlock;
+    uint256 prevkey;
+    std::map<uint32_t, Coin> outputs;
     while (pcursor->Valid()) {
         boost::this_thread::interruption_point();
-        uint256 key;
-        CCoins coins;
-        if (pcursor->GetKey(key) && pcursor->GetValue(coins)) {
-            std::map<uint32_t, Coin> outputs;
-            for (unsigned int i=0; i<coins.vout.size(); i++) {
-                CTxOut &out = coins.vout[i];
-                if (!out.IsNull()) {
-                    outputs[i] = Coin(std::move(out), coins.nHeight, coins.fCoinBase);
-                }
+        COutPoint key;
+        Coin coin;
+        if (pcursor->GetKey(key) && pcursor->GetValue(coin)) {
+            if (!outputs.empty() && key.hash != prevkey) {
+                ApplyStats(stats, ss, prevkey, outputs);
+                outputs.clear();
             }
-            ApplyStats(stats, ss, key, outputs);
+            prevkey = key.hash;
+            outputs[key.n] = std::move(coin);
         } else {
             return error("%s: unable to read value", __func__);
         }
         pcursor->Next();
     }
+    if (!outputs.empty()) {
+        ApplyStats(stats, ss, prevkey, outputs);
+    }
     stats.hashSerialized = ss.GetHash();
     stats.nDiskSize = view->EstimateSize();
     return true;
@@ -973,35 +976,37 @@ UniValue gettxout(const JSONRPCRequest& request)
     std::string strHash = request.params[0].get_str();
     uint256 hash(uint256S(strHash));
     int n = request.params[1].get_int();
+    COutPoint out(hash, n);
     bool fMempool = true;
     if (request.params.size() > 2)
         fMempool = request.params[2].get_bool();
 
-    CCoins coins;
+    Coin coin;
     if (fMempool) {
         LOCK(mempool.cs);
         CCoinsViewMemPool view(pcoinsTip, mempool);
-        if (!view.GetCoins(hash, coins) || mempool.isSpent(COutPoint(hash, n))) // TODO: this should be done by the CCoinsViewMemPool
+        if (!view.GetCoins(out, coin) || mempool.isSpent(out)) { // TODO: filtering spent coins should be done by the CCoinsViewMemPool
             return NullUniValue;
+        }
     } else {
-        if (!pcoinsTip->GetCoins(hash, coins))
+        if (!pcoinsTip->GetCoins(out, coin)) {
             return NullUniValue;
+        }
     }
-    if (n<0 || (unsigned int)n>=coins.vout.size() || coins.vout[n].IsNull())
-        return NullUniValue;
 
     BlockMap::iterator it = mapBlockIndex.find(pcoinsTip->GetBestBlock());
     CBlockIndex *pindex = it->second;
     ret.push_back(Pair("bestblock", pindex->GetBlockHash().GetHex()));
-    if ((unsigned int)coins.nHeight == MEMPOOL_HEIGHT)
+    if (coin.nHeight == MEMPOOL_HEIGHT) {
         ret.push_back(Pair("confirmations", 0));
-    else
-        ret.push_back(Pair("confirmations", pindex->nHeight - coins.nHeight + 1));
-    ret.push_back(Pair("value", ValueFromAmount(coins.vout[n].nValue)));
+    } else {
+        ret.push_back(Pair("confirmations", (int64_t)(pindex->nHeight - coin.nHeight + 1)));
+    }
+    ret.push_back(Pair("value", ValueFromAmount(coin.out.nValue)));
     UniValue o(UniValue::VOBJ);
-    ScriptPubKeyToUniv(coins.vout[n].scriptPubKey, o, true);
+    ScriptPubKeyToUniv(coin.out.scriptPubKey, o, true);
     ret.push_back(Pair("scriptPubKey", o));
-    ret.push_back(Pair("coinbase", coins.fCoinBase));
+    ret.push_back(Pair("coinbase", (bool)coin.fCoinBase));
 
     return ret;
 }
diff --git a/src/rpc/rawtransaction.cpp b/src/rpc/rawtransaction.cpp
index 3f7b6adead..8ecbf9ede5 100644
--- a/src/rpc/rawtransaction.cpp
+++ b/src/rpc/rawtransaction.cpp
@@ -219,9 +219,10 @@ UniValue gettxoutproof(const JSONRPCRequest& request)
             throw JSONRPCError(RPC_INVALID_ADDRESS_OR_KEY, "Block not found");
         pblockindex = mapBlockIndex[hashBlock];
     } else {
-        CCoins coins;
-        if (pcoinsTip->GetCoins(oneTxid, coins) && coins.nHeight > 0 && coins.nHeight <= chainActive.Height())
-            pblockindex = chainActive[coins.nHeight];
+        const Coin& coin = AccessByTxid(*pcoinsTip, oneTxid);
+        if (!coin.IsPruned() && coin.nHeight > 0 && coin.nHeight <= chainActive.Height()) {
+            pblockindex = chainActive[coin.nHeight];
+        }
     }
 
     if (pblockindex == NULL)