1  // Copyright (c) 2009-2010 Satoshi Nakamoto
 2  // Copyright (c) 2009-present 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  #include <util/feefrac.h>
12  
13  
14  #include <cstdint>
15  #include <string>
16  #include <type_traits>
17  
18  const std::string CURRENCY_UNIT = "BTC"; // One formatted unit
19  const std::string CURRENCY_ATOM = "sat"; // One indivisible minimum value unit
20  
21  /* Used to determine type of fee estimation requested */
22  enum class FeeEstimateMode {
23      UNSET,        //!< Use default settings based on other criteria
24      ECONOMICAL,   //!< Force estimateSmartFee to use non-conservative estimates
25      CONSERVATIVE, //!< Force estimateSmartFee to use conservative estimates
26      BTC_KVB,      //!< Use BTC/kvB fee rate unit
27      SAT_VB,       //!< Use sat/vB fee rate unit
28  };
29  
30  /**
31   * Fee rate in satoshis per virtualbyte: CAmount / vB
32   * the feerate is represented internally as FeeFrac
33   */
34  class CFeeRate
35  {
36  private:
37      /** Fee rate in sats/vB (satoshis per N virtualbytes) */
38      FeePerVSize m_feerate;
39  
40  public:
41      /** Fee rate of 0 satoshis per 0 vB */
42      CFeeRate() = default;
43      template<std::integral I> // Disallow silent float -> int conversion
44      explicit CFeeRate(const I m_feerate_kvb) : m_feerate(FeePerVSize(m_feerate_kvb, 1000)) {}
45  
46      /**
47       * Construct a fee rate from a fee in satoshis and a vsize in vB.
48       *
49       * Passing any virtual_bytes less than or equal to 0 will result in 0 fee rate per 0 size.
50       */
51      CFeeRate(const CAmount& nFeePaid, int32_t virtual_bytes);
52  
53      /**
54       * Return the fee in satoshis for the given vsize in vbytes.
55       * If the calculated fee would have fractional satoshis, then the
56       * returned fee will always be rounded up to the nearest satoshi.
57       */
58      CAmount GetFee(int32_t virtual_bytes) const;
59  
60      FeePerVSize GetFeePerVSize() const { return m_feerate; }
61  
62      /**
63       * Return the fee in satoshis for a vsize of 1000 vbytes
64       */
65      CAmount GetFeePerK() const { return CAmount(m_feerate.EvaluateFeeDown(1000)); }
66      friend std::weak_ordering operator<=>(const CFeeRate& a, const CFeeRate& b) noexcept
67      {
68          return FeeRateCompare(a.m_feerate, b.m_feerate);
69      }
70      friend bool operator==(const CFeeRate& a, const CFeeRate& b) noexcept
71      {
72          return FeeRateCompare(a.m_feerate, b.m_feerate) == std::weak_ordering::equivalent;
73      }
74      CFeeRate& operator+=(const CFeeRate& a) {
75          m_feerate = FeePerVSize(GetFeePerK() + a.GetFeePerK(), 1000);
76          return *this;
77      }
78      std::string ToString(const FeeEstimateMode& fee_estimate_mode = FeeEstimateMode::BTC_KVB) const;
79      friend CFeeRate operator*(const CFeeRate& f, int a) { return CFeeRate(a * f.m_feerate.fee, f.m_feerate.size); }
80      friend CFeeRate operator*(int a, const CFeeRate& f) { return CFeeRate(a * f.m_feerate.fee, f.m_feerate.size); }
81  
82      SERIALIZE_METHODS(CFeeRate, obj) { READWRITE(obj.m_feerate.fee, obj.m_feerate.size); }
83  };
84  
85  #endif // BITCOIN_POLICY_FEERATE_H