Refactor fee rules to make them actually readable.

This (nearly) doesn't change fee rules at all:
 * To make it into the fee transaction area, the dPriority comparison
   changed from < to <=
 * We now just ignore transactions > MAX_BLOCK_SIZE/4 instead of
   doing some calculations to require increasingly large fees as
   size increases.

src/main.cpp

@@ -634,30 +634,23 @@ bool CheckTransaction(const CTransaction& tx, CValidationState &state)
     return true;
 }
 
-int64 GetMinFee(const CTransaction& tx, unsigned int nBlockSize, bool fAllowFree, enum GetMinFee_mode mode)
+int64 GetMinFee(const CTransaction& tx, bool fAllowFree, enum GetMinFee_mode mode)
 {
     // Base fee is either nMinTxFee or nMinRelayTxFee
     int64 nBaseFee = (mode == GMF_RELAY) ? tx.nMinRelayTxFee : tx.nMinTxFee;
 
     unsigned int nBytes = ::GetSerializeSize(tx, SER_NETWORK, PROTOCOL_VERSION);
-    unsigned int nNewBlockSize = nBlockSize + nBytes;
     int64 nMinFee = (1 + (int64)nBytes / 1000) * nBaseFee;
 
     if (fAllowFree)
     {
-        if (nBlockSize == 1)
-        {
-            // Transactions under 10K are free
-            // (about 4500 BTC if made of 50 BTC inputs)
-            if (nBytes < 10000)
-                nMinFee = 0;
-        }
-        else
-        {
-            // Free transaction area
-            if (nNewBlockSize < 27000)
-                nMinFee = 0;
-        }
+        // There is a free transaction area in blocks created by most miners,
+        // * If we are relaying we allow transactions up to DEFAULT_BLOCK_PRIORITY_SIZE - 1000
+        //   to be considered to fall into this category
+        // * If we are creating a transaction we allow transactions up to DEFAULT_BLOCK_PRIORITY_SIZE - 17000
+        //   (= 10000) to be considered safe and assume they can likely make it into this section
+        if (nBytes < (mode == GMF_SEND ? (DEFAULT_BLOCK_PRIORITY_SIZE - 17000) : (DEFAULT_BLOCK_PRIORITY_SIZE - 1000)))
+            nMinFee = 0;
     }
 
     // To limit dust spam, require base fee if any output is less than 0.01
@@ -668,14 +661,6 @@ int64 GetMinFee(const CTransaction& tx, unsigned int nBlockSize, bool fAllowFree
                 nMinFee = nBaseFee;
     }
 
-    // Raise the price as the block approaches full
-    if (nBlockSize != 1 && nNewBlockSize >= MAX_BLOCK_SIZE_GEN/2)
-    {
-        if (nNewBlockSize >= MAX_BLOCK_SIZE_GEN)
-            return MAX_MONEY;
-        nMinFee *= MAX_BLOCK_SIZE_GEN / (MAX_BLOCK_SIZE_GEN - nNewBlockSize);
-    }
-
     if (!MoneyRange(nMinFee))
         nMinFee = MAX_MONEY;
     return nMinFee;
@@ -799,7 +784,7 @@ bool CTxMemPool::accept(CValidationState &state, CTransaction &tx, bool fCheckIn
         unsigned int nSize = ::GetSerializeSize(tx, SER_NETWORK, PROTOCOL_VERSION);
 
         // Don't accept it if it can't get into a block
-        int64 txMinFee = GetMinFee(tx, 1000, true, GMF_RELAY);
+        int64 txMinFee = GetMinFee(tx, true, GMF_RELAY);
         if (fLimitFree && nFees < txMinFee)
             return error("CTxMemPool::accept() : not enough fees %s, %"PRI64d" < %"PRI64d,
                          hash.ToString().c_str(),
@@ -4187,7 +4172,7 @@ CBlockTemplate* CreateNewBlock(CReserveKey& reservekey)
 
     // How much of the block should be dedicated to high-priority transactions,
     // included regardless of the fees they pay
-    unsigned int nBlockPrioritySize = GetArg("-blockprioritysize", 27000);
+    unsigned int nBlockPrioritySize = GetArg("-blockprioritysize", DEFAULT_BLOCK_PRIORITY_SIZE);
     nBlockPrioritySize = std::min(nBlockMaxSize, nBlockPrioritySize);
 
     // Minimum block size you want to create; block will be filled with free transactions
@@ -4315,7 +4300,7 @@ CBlockTemplate* CreateNewBlock(CReserveKey& reservekey)
             // Prioritize by fee once past the priority size or we run out of high-priority
             // transactions:
             if (!fSortedByFee &&
-                ((nBlockSize + nTxSize >= nBlockPrioritySize) || (dPriority < COIN * 144 / 250)))
+                ((nBlockSize + nTxSize >= nBlockPrioritySize) || !AllowFree(dPriority)))
             {
                 fSortedByFee = true;
                 comparer = TxPriorityCompare(fSortedByFee);

src/main.h

@@ -52,6 +52,8 @@ static const int COINBASE_MATURITY = 100;
 static const unsigned int LOCKTIME_THRESHOLD = 500000000; // Tue Nov  5 00:53:20 1985 UTC
 /** Maximum number of script-checking threads allowed */
 static const int MAX_SCRIPTCHECK_THREADS = 16;
+/** Default amount of block size reserved for high-priority transactions (in bytes) */
+static const int DEFAULT_BLOCK_PRIORITY_SIZE = 27000;
 #ifdef USE_UPNP
 static const int fHaveUPnP = true;
 #else
@@ -262,12 +264,11 @@ struct CDiskTxPos : public CDiskBlockPos
 
 enum GetMinFee_mode
 {
-    GMF_BLOCK,
     GMF_RELAY,
     GMF_SEND,
 };
 
-int64 GetMinFee(const CTransaction& tx, unsigned int nBlockSize = 1, bool fAllowFree = true, enum GetMinFee_mode mode = GMF_BLOCK);
+int64 GetMinFee(const CTransaction& tx, bool fAllowFree, enum GetMinFee_mode mode);
 
 //
 // Check transaction inputs, and make sure any

src/wallet.cpp

@@ -1301,7 +1301,7 @@ bool CWallet::CreateTransaction(const vector<pair<CScript, int64> >& vecSend,
                 // Check that enough fee is included
                 int64 nPayFee = nTransactionFee * (1 + (int64)nBytes / 1000);
                 bool fAllowFree = AllowFree(dPriority);
-                int64 nMinFee = GetMinFee(wtxNew, 1, fAllowFree, GMF_SEND);
+                int64 nMinFee = GetMinFee(wtxNew, fAllowFree, GMF_SEND);
                 if (nFeeRet < max(nPayFee, nMinFee))
                 {
                     nFeeRet = max(nPayFee, nMinFee);