1  // Copyright (c) 2009-2010 Satoshi Nakamoto
 2  // Copyright (c) 2009-2022 The Bitcoin Core developers
 3  // Distributed under the MIT software license, see the accompanying
 4  // file COPYING or http://www.opensource.org/licenses/mit-license.php.
 5  
 6  #ifndef BITCOIN_POLICY_FEERATE_H
 7  #define BITCOIN_POLICY_FEERATE_H
 8  
 9  #include <consensus/amount.h>
10  #include <serialize.h>
11  
12  
13  #include <cstdint>
14  #include <string>
15  #include <type_traits>
16  
17  const std::string CURRENCY_UNIT = "BTC"; // One formatted unit
18  const std::string CURRENCY_ATOM = "sat"; // One indivisible minimum value unit
19  
20  /* Used to determine type of fee estimation requested */
21  enum class FeeEstimateMode {
22      UNSET,        //!< Use default settings based on other criteria
23      ECONOMICAL,   //!< Force estimateSmartFee to use non-conservative estimates
24      CONSERVATIVE, //!< Force estimateSmartFee to use conservative estimates
25      BTC_KVB,      //!< Use BTC/kvB fee rate unit
26      SAT_VB,       //!< Use sat/vB fee rate unit
27  };
28  
29  /**
30   * Fee rate in satoshis per kilovirtualbyte: CAmount / kvB
31   */
32  class CFeeRate
33  {
34  private:
35      /** Fee rate in sat/kvB (satoshis per 1000 virtualbytes) */
36      CAmount nSatoshisPerK;
37  
38  public:
39      /** Fee rate of 0 satoshis per kvB */
40      CFeeRate() : nSatoshisPerK(0) { }
41      template<typename I>
42      explicit CFeeRate(const I _nSatoshisPerK): nSatoshisPerK(_nSatoshisPerK) {
43          // We've previously had bugs creep in from silent double->int conversion...
44          static_assert(std::is_integral<I>::value, "CFeeRate should be used without floats");
45      }
46  
47      /**
48       * Construct a fee rate from a fee in satoshis and a vsize in vB.
49       *
50       * param@[in]   nFeePaid    The fee paid by a transaction, in satoshis
51       * param@[in]   num_bytes   The vsize of a transaction, in vbytes
52       */
53      CFeeRate(const CAmount& nFeePaid, uint32_t num_bytes);
54  
55      /**
56       * Return the fee in satoshis for the given vsize in vbytes.
57       * If the calculated fee would have fractional satoshis, then the
58       * returned fee will always be rounded up to the nearest satoshi.
59       */
60      CAmount GetFee(uint32_t num_bytes) const;
61  
62      /**
63       * Return the fee in satoshis for a vsize of 1000 vbytes
64       */
65      CAmount GetFeePerK() const { return nSatoshisPerK; }
66      friend bool operator<(const CFeeRate& a, const CFeeRate& b) { return a.nSatoshisPerK < b.nSatoshisPerK; }
67      friend bool operator>(const CFeeRate& a, const CFeeRate& b) { return a.nSatoshisPerK > b.nSatoshisPerK; }
68      friend bool operator==(const CFeeRate& a, const CFeeRate& b) { return a.nSatoshisPerK == b.nSatoshisPerK; }
69      friend bool operator<=(const CFeeRate& a, const CFeeRate& b) { return a.nSatoshisPerK <= b.nSatoshisPerK; }
70      friend bool operator>=(const CFeeRate& a, const CFeeRate& b) { return a.nSatoshisPerK >= b.nSatoshisPerK; }
71      friend bool operator!=(const CFeeRate& a, const CFeeRate& b) { return a.nSatoshisPerK != b.nSatoshisPerK; }
72      CFeeRate& operator+=(const CFeeRate& a) { nSatoshisPerK += a.nSatoshisPerK; return *this; }
73      std::string ToString(const FeeEstimateMode& fee_estimate_mode = FeeEstimateMode::BTC_KVB) const;
74      friend CFeeRate operator*(const CFeeRate& f, int a) { return CFeeRate(a * f.nSatoshisPerK); }
75      friend CFeeRate operator*(int a, const CFeeRate& f) { return CFeeRate(a * f.nSatoshisPerK); }
76  
77      SERIALIZE_METHODS(CFeeRate, obj) { READWRITE(obj.nSatoshisPerK); }
78  };
79  
80  #endif // BITCOIN_POLICY_FEERATE_H