From c26649f9ed03fa9505e44aaf7f8cfdaa81f734cc Mon Sep 17 00:00:00 2001
From: Alex Morcos <morcos@chaincode.com>
Date: Tue, 26 Aug 2014 12:59:21 -0400
Subject: [PATCH] Track modified size in TxMemPoolEntry so that we can
 correctly compute priority.

---
 src/core.cpp      | 12 ++++++++++--
 src/core.h        |  3 +++
 src/txmempool.cpp |  4 +++-
 src/txmempool.h   |  1 +
 4 files changed, 17 insertions(+), 3 deletions(-)

diff --git a/src/core.cpp b/src/core.cpp
index 8dcda0126..491e4fa68 100644
--- a/src/core.cpp
+++ b/src/core.cpp
@@ -123,6 +123,14 @@ int64_t CTransaction::GetValueOut() const
 }
 
 double CTransaction::ComputePriority(double dPriorityInputs, unsigned int nTxSize) const
+{
+    nTxSize = CalculateModifiedSize(nTxSize);
+    if (nTxSize == 0) return 0.0;
+
+    return dPriorityInputs / nTxSize;
+}
+
+unsigned int CTransaction::CalculateModifiedSize(unsigned int nTxSize) const
 {
     // In order to avoid disincentivizing cleaning up the UTXO set we don't count
     // the constant overhead for each txin and up to 110 bytes of scriptSig (which
@@ -131,14 +139,14 @@ double CTransaction::ComputePriority(double dPriorityInputs, unsigned int nTxSiz
     // risk encouraging people to create junk outputs to redeem later.
     if (nTxSize == 0)
         nTxSize = ::GetSerializeSize(*this, SER_NETWORK, PROTOCOL_VERSION);
+
     BOOST_FOREACH(const CTxIn& txin, vin)
     {
         unsigned int offset = 41U + std::min(110U, (unsigned int)txin.scriptSig.size());
         if (nTxSize > offset)
             nTxSize -= offset;
     }
-    if (nTxSize == 0) return 0.0;
-    return dPriorityInputs / nTxSize;
+    return nTxSize;
 }
 
 std::string CTransaction::ToString() const
diff --git a/src/core.h b/src/core.h
index 34c00c414..1233fbde6 100644
--- a/src/core.h
+++ b/src/core.h
@@ -284,6 +284,9 @@ public:
     // Compute priority, given priority of inputs and (optionally) tx size
     double ComputePriority(double dPriorityInputs, unsigned int nTxSize=0) const;
 
+    // Compute modified tx size for priority calculation (optionally given tx size)
+    unsigned int CalculateModifiedSize(unsigned int nTxSize=0) const;
+
     bool IsCoinBase() const
     {
         return (vin.size() == 1 && vin[0].prevout.IsNull());
diff --git a/src/txmempool.cpp b/src/txmempool.cpp
index 238d5bab1..acdf51c95 100644
--- a/src/txmempool.cpp
+++ b/src/txmempool.cpp
@@ -23,6 +23,8 @@ CTxMemPoolEntry::CTxMemPoolEntry(const CTransaction& _tx, int64_t _nFee,
     tx(_tx), nFee(_nFee), nTime(_nTime), dPriority(_dPriority), nHeight(_nHeight)
 {
     nTxSize = ::GetSerializeSize(tx, SER_NETWORK, PROTOCOL_VERSION);
+
+    nModSize = tx.CalculateModifiedSize(nTxSize);
 }
 
 CTxMemPoolEntry::CTxMemPoolEntry(const CTxMemPoolEntry& other)
@@ -34,7 +36,7 @@ double
 CTxMemPoolEntry::GetPriority(unsigned int currentHeight) const
 {
     int64_t nValueIn = tx.GetValueOut()+nFee;
-    double deltaPriority = ((double)(currentHeight-nHeight)*nValueIn)/nTxSize;
+    double deltaPriority = ((double)(currentHeight-nHeight)*nValueIn)/nModSize;
     double dResult = dPriority + deltaPriority;
     return dResult;
 }
diff --git a/src/txmempool.h b/src/txmempool.h
index 360364d8b..b9d50ee0b 100644
--- a/src/txmempool.h
+++ b/src/txmempool.h
@@ -31,6 +31,7 @@ private:
     CTransaction tx;
     int64_t nFee; // Cached to avoid expensive parent-transaction lookups
     size_t nTxSize; // ... and avoid recomputing tx size
+    size_t nModSize; // ... and modified size for priority
     int64_t nTime; // Local time when entering the mempool
     double dPriority; // Priority when entering the mempool
     unsigned int nHeight; // Chain height when entering the mempool