Consensus: Policy: MOVEONLY: Move CFeeRate out of the consensus module

...from amount.o to policy/feerate.o

Policy, because it moves policy code to the policy directory (common module)

src/policy/feerate.cpp

@@ -0,0 +1,43 @@
+// Copyright (c) 2009-2010 Satoshi Nakamoto
+// Copyright (c) 2009-2016 The Bitcoin Core developers
+// Distributed under the MIT software license, see the accompanying
+// file COPYING or http://www.opensource.org/licenses/mit-license.php.
+
+#include "feerate.h"
+
+#include "tinyformat.h"
+
+const std::string CURRENCY_UNIT = "BTC";
+
+CFeeRate::CFeeRate(const CAmount& nFeePaid, size_t nBytes_)
+{
+    assert(nBytes_ <= uint64_t(std::numeric_limits<int64_t>::max()));
+    int64_t nSize = int64_t(nBytes_);
+
+    if (nSize > 0)
+        nSatoshisPerK = nFeePaid * 1000 / nSize;
+    else
+        nSatoshisPerK = 0;
+}
+
+CAmount CFeeRate::GetFee(size_t nBytes_) const
+{
+    assert(nBytes_ <= uint64_t(std::numeric_limits<int64_t>::max()));
+    int64_t nSize = int64_t(nBytes_);
+
+    CAmount nFee = nSatoshisPerK * nSize / 1000;
+
+    if (nFee == 0 && nSize != 0) {
+        if (nSatoshisPerK > 0)
+            nFee = CAmount(1);
+        if (nSatoshisPerK < 0)
+            nFee = CAmount(-1);
+    }
+
+    return nFee;
+}
+
+std::string CFeeRate::ToString() const
+{
+    return strprintf("%d.%08d %s/kB", nSatoshisPerK / COIN, nSatoshisPerK % COIN, CURRENCY_UNIT);
+}