Type-safe CFeeRate class

Use CFeeRate instead of an int64_t for quantities that are
fee-per-size.

Helps prevent unit-conversion mismatches between the wallet,
relaying, and mining code.

1 files changed, 22 insertions, 20 deletions

diff --git a/src/miner.cpp b/src/miner.cpp
index 94fc8e3888..4e131c088b 100644
--- a/src/miner.cpp
+++ b/src/miner.cpp
@@ -52,25 +52,30 @@ void SHA256Transform(void* pstate, void* pinput, const void* pinit)
         ((uint32_t*)pstate)[i] = ctx.h[i];
 }
 
-// Some explaining would be appreciated
+//
+// Unconfirmed transactions in the memory pool often depend on other
+// transactions in the memory pool. When we select transactions from the
+// pool, we select by highest priority or fee rate, so we might consider
+// transactions that depend on transactions that aren't yet in the block.
+// The COrphan class keeps track of these 'temporary orphans' while
+// CreateBlock is figuring out which transactions to include.
+//
 class COrphan
 {
 public:
     const CTransaction* ptx;
     set<uint256> setDependsOn;
     double dPriority;
-    double dFeePerKb;
+    CFeeRate feeRate;
 
-    COrphan(const CTransaction* ptxIn)
+    COrphan(const CTransaction* ptxIn) : ptx(ptxIn), feeRate(0), dPriority(0)
     {
-        ptx = ptxIn;
-        dPriority = dFeePerKb = 0;
     }
 
     void print() const
     {
-        LogPrintf("COrphan(hash=%s, dPriority=%.1f, dFeePerKb=%.1f)\n",
-               ptx->GetHash().ToString(), dPriority, dFeePerKb);
+        LogPrintf("COrphan(hash=%s, dPriority=%.1f, fee=%s)\n",
+                  ptx->GetHash().ToString(), dPriority, feeRate.ToString());
         BOOST_FOREACH(uint256 hash, setDependsOn)
             LogPrintf("   setDependsOn %s\n", hash.ToString());
     }
@@ -80,8 +85,8 @@ public:
 uint64_t nLastBlockTx = 0;
 uint64_t nLastBlockSize = 0;
 
-// We want to sort transactions by priority and fee, so:
-typedef boost::tuple<double, double, const CTransaction*> TxPriority;
+// We want to sort transactions by priority and fee rate, so:
+typedef boost::tuple<double, CFeeRate, const CTransaction*> TxPriority;
 class TxPriorityCompare
 {
     bool byFee;
@@ -210,18 +215,15 @@ CBlockTemplate* CreateNewBlock(const CScript& scriptPubKeyIn)
             unsigned int nTxSize = ::GetSerializeSize(tx, SER_NETWORK, PROTOCOL_VERSION);
             dPriority = tx.ComputePriority(dPriority, nTxSize);
 
-            // This is a more accurate fee-per-kilobyte than is used by the client code, because the
-            // client code rounds up the size to the nearest 1K. That's good, because it gives an
-            // incentive to create smaller transactions.
-            double dFeePerKb =  double(nTotalIn-tx.GetValueOut()) / (double(nTxSize)/1000.0);
+            CFeeRate feeRate(nTotalIn-tx.GetValueOut(), nTxSize);
 
             if (porphan)
             {
                 porphan->dPriority = dPriority;
-                porphan->dFeePerKb = dFeePerKb;
+                porphan->feeRate = feeRate;
             }
             else
-                vecPriority.push_back(TxPriority(dPriority, dFeePerKb, &mi->second.GetTx()));
+                vecPriority.push_back(TxPriority(dPriority, feeRate, &mi->second.GetTx()));
         }
 
         // Collect transactions into block
@@ -237,7 +239,7 @@ CBlockTemplate* CreateNewBlock(const CScript& scriptPubKeyIn)
         {
             // Take highest priority transaction off the priority queue:
             double dPriority = vecPriority.front().get<0>();
-            double dFeePerKb = vecPriority.front().get<1>();
+            CFeeRate feeRate = vecPriority.front().get<1>();
             const CTransaction& tx = *(vecPriority.front().get<2>());
 
             std::pop_heap(vecPriority.begin(), vecPriority.end(), comparer);
@@ -254,7 +256,7 @@ CBlockTemplate* CreateNewBlock(const CScript& scriptPubKeyIn)
                 continue;
 
             // Skip free transactions if we're past the minimum block size:
-            if (fSortedByFee && (dFeePerKb < CTransaction::nMinRelayTxFee) && (nBlockSize + nTxSize >= nBlockMinSize))
+            if (fSortedByFee && (feeRate < CTransaction::minRelayTxFee) && (nBlockSize + nTxSize >= nBlockMinSize))
                 continue;
 
             // Prioritize by fee once past the priority size or we run out of high-priority
@@ -298,8 +300,8 @@ CBlockTemplate* CreateNewBlock(const CScript& scriptPubKeyIn)
 
             if (fPrintPriority)
             {
-                LogPrintf("priority %.1f feeperkb %.1f txid %s\n",
-                       dPriority, dFeePerKb, tx.GetHash().ToString());
+                LogPrintf("priority %.1f fee %s txid %s\n",
+                          dPriority, feeRate.ToString(), tx.GetHash().ToString());
             }
 
             // Add transactions that depend on this one to the priority queue
@@ -312,7 +314,7 @@ CBlockTemplate* CreateNewBlock(const CScript& scriptPubKeyIn)
                         porphan->setDependsOn.erase(hash);
                         if (porphan->setDependsOn.empty())
                         {
-                            vecPriority.push_back(TxPriority(porphan->dPriority, porphan->dFeePerKb, porphan->ptx));
+                            vecPriority.push_back(TxPriority(porphan->dPriority, porphan->feeRate, porphan->ptx));
                             std::push_heap(vecPriority.begin(), vecPriority.end(), comparer);
                         }
                     }