LCOV - code coverage report
Current view: top level - src/wallet - coinselection.h (source / functions) Hit Total Coverage
Test: fuzz_coverage.info Lines: 0 99 0.0 %
Date: 2023-10-05 12:38:51 Functions: 0 41 0.0 %
Branches: 0 42 0.0 %

           Branch data     Line data    Source code
       1                 :            : // Copyright (c) 2017-2022 The Bitcoin Core developers
       2                 :            : // Distributed under the MIT software license, see the accompanying
       3                 :            : // file COPYING or http://www.opensource.org/licenses/mit-license.php.
       4                 :            : 
       5                 :            : #ifndef BITCOIN_WALLET_COINSELECTION_H
       6                 :            : #define BITCOIN_WALLET_COINSELECTION_H
       7                 :            : 
       8                 :            : #include <consensus/amount.h>
       9                 :            : #include <consensus/consensus.h>
      10                 :            : #include <outputtype.h>
      11                 :            : #include <policy/feerate.h>
      12                 :            : #include <primitives/transaction.h>
      13                 :            : #include <random.h>
      14                 :            : #include <util/check.h>
      15                 :            : #include <util/insert.h>
      16                 :            : #include <util/result.h>
      17                 :            : 
      18                 :            : #include <optional>
      19                 :            : 
      20                 :            : 
      21                 :            : namespace wallet {
      22                 :            : //! lower bound for randomly-chosen target change amount
      23                 :            : static constexpr CAmount CHANGE_LOWER{50000};
      24                 :            : //! upper bound for randomly-chosen target change amount
      25                 :            : static constexpr CAmount CHANGE_UPPER{1000000};
      26                 :            : 
      27                 :            : /** A UTXO under consideration for use in funding a new transaction. */
      28                 :            : struct COutput {
      29                 :            : private:
      30                 :            :     /** The output's value minus fees required to spend it and bump its unconfirmed ancestors to the target feerate. */
      31                 :            :     std::optional<CAmount> effective_value;
      32                 :            : 
      33                 :            :     /** The fee required to spend this output at the transaction's target feerate and to bump its unconfirmed ancestors to the target feerate. */
      34                 :            :     std::optional<CAmount> fee;
      35                 :            : 
      36                 :            : public:
      37                 :            :     /** The outpoint identifying this UTXO */
      38                 :            :     COutPoint outpoint;
      39                 :            : 
      40                 :            :     /** The output itself */
      41                 :            :     CTxOut txout;
      42                 :            : 
      43                 :            :     /**
      44                 :            :      * Depth in block chain.
      45                 :            :      * If > 0: the tx is on chain and has this many confirmations.
      46                 :            :      * If = 0: the tx is waiting confirmation.
      47                 :            :      * If < 0: a conflicting tx is on chain and has this many confirmations. */
      48                 :            :     int depth;
      49                 :            : 
      50                 :            :     /** Pre-computed estimated size of this output as a fully-signed input in a transaction. Can be -1 if it could not be calculated */
      51                 :            :     int input_bytes;
      52                 :            : 
      53                 :            :     /** Whether we have the private keys to spend this output */
      54                 :            :     bool spendable;
      55                 :            : 
      56                 :            :     /** Whether we know how to spend this output, ignoring the lack of keys */
      57                 :            :     bool solvable;
      58                 :            : 
      59                 :            :     /**
      60                 :            :      * Whether this output is considered safe to spend. Unconfirmed transactions
      61                 :            :      * from outside keys and unconfirmed replacement transactions are considered
      62                 :            :      * unsafe and will not be used to fund new spending transactions.
      63                 :            :      */
      64                 :            :     bool safe;
      65                 :            : 
      66                 :            :     /** The time of the transaction containing this output as determined by CWalletTx::nTimeSmart */
      67                 :            :     int64_t time;
      68                 :            : 
      69                 :            :     /** Whether the transaction containing this output is sent from the owning wallet */
      70                 :            :     bool from_me;
      71                 :            : 
      72                 :            :     /** The fee required to spend this output at the consolidation feerate. */
      73                 :          0 :     CAmount long_term_fee{0};
      74                 :            : 
      75                 :            :     /** The fee necessary to bump this UTXO's ancestor transactions to the target feerate */
      76                 :          0 :     CAmount ancestor_bump_fees{0};
      77                 :            : 
      78                 :          0 :     COutput(const COutPoint& outpoint, const CTxOut& txout, int depth, int input_bytes, bool spendable, bool solvable, bool safe, int64_t time, bool from_me, const std::optional<CFeeRate> feerate = std::nullopt)
      79                 :          0 :         : outpoint{outpoint},
      80                 :          0 :           txout{txout},
      81                 :          0 :           depth{depth},
      82                 :          0 :           input_bytes{input_bytes},
      83                 :          0 :           spendable{spendable},
      84                 :          0 :           solvable{solvable},
      85                 :          0 :           safe{safe},
      86                 :          0 :           time{time},
      87                 :          0 :           from_me{from_me}
      88                 :            :     {
      89         [ #  # ]:          0 :         if (feerate) {
      90                 :            :             // base fee without considering potential unconfirmed ancestors
      91   [ #  #  #  #  :          0 :             fee = input_bytes < 0 ? 0 : feerate.value().GetFee(input_bytes);
             #  #  #  # ]
      92   [ #  #  #  # ]:          0 :             effective_value = txout.nValue - fee.value();
      93                 :          0 :         }
      94                 :          0 :     }
      95                 :            : 
      96                 :          0 :     COutput(const COutPoint& outpoint, const CTxOut& txout, int depth, int input_bytes, bool spendable, bool solvable, bool safe, int64_t time, bool from_me, const CAmount fees)
      97                 :          0 :         : COutput(outpoint, txout, depth, input_bytes, spendable, solvable, safe, time, from_me)
      98                 :            :     {
      99                 :            :         // if input_bytes is unknown, then fees should be 0, if input_bytes is known, then the fees should be a positive integer or 0 (input_bytes known and fees = 0 only happens in the tests)
     100                 :          0 :         assert((input_bytes < 0 && fees == 0) || (input_bytes > 0 && fees >= 0));
     101                 :          0 :         fee = fees;
     102                 :          0 :         effective_value = txout.nValue - fee.value();
     103                 :          0 :     }
     104                 :            : 
     105                 :            :     std::string ToString() const;
     106                 :            : 
     107                 :            :     bool operator<(const COutput& rhs) const
     108                 :            :     {
     109                 :            :         return outpoint < rhs.outpoint;
     110                 :            :     }
     111                 :            : 
     112                 :          0 :     void ApplyBumpFee(CAmount bump_fee)
     113                 :            :     {
     114         [ #  # ]:          0 :         assert(bump_fee >= 0);
     115                 :          0 :         ancestor_bump_fees = bump_fee;
     116         [ #  # ]:          0 :         assert(fee);
     117                 :          0 :         *fee += bump_fee;
     118                 :            :         // Note: assert(effective_value - bump_fee == nValue - fee.value());
     119                 :          0 :         effective_value = txout.nValue - fee.value();
     120                 :          0 :     }
     121                 :            : 
     122                 :          0 :     CAmount GetFee() const
     123                 :            :     {
     124         [ #  # ]:          0 :         assert(fee.has_value());
     125                 :          0 :         return fee.value();
     126                 :            :     }
     127                 :            : 
     128                 :          0 :     CAmount GetEffectiveValue() const
     129                 :            :     {
     130         [ #  # ]:          0 :         assert(effective_value.has_value());
     131                 :          0 :         return effective_value.value();
     132                 :            :     }
     133                 :            : 
     134                 :          0 :     bool HasEffectiveValue() const { return effective_value.has_value(); }
     135                 :            : };
     136                 :            : 
     137                 :            : /** Parameters for one iteration of Coin Selection. */
     138                 :            : struct CoinSelectionParams {
     139                 :            :     /** Randomness to use in the context of coin selection. */
     140                 :            :     FastRandomContext& rng_fast;
     141                 :            :     /** Size of a change output in bytes, determined by the output type. */
     142                 :          0 :     size_t change_output_size = 0;
     143                 :            :     /** Size of the input to spend a change output in virtual bytes. */
     144                 :          0 :     size_t change_spend_size = 0;
     145                 :            :     /** Mininmum change to target in Knapsack solver: select coins to cover the payment and
     146                 :            :      * at least this value of change. */
     147                 :          0 :     CAmount m_min_change_target{0};
     148                 :            :     /** Minimum amount for creating a change output.
     149                 :            :      * If change budget is smaller than min_change then we forgo creation of change output.
     150                 :            :      */
     151                 :          0 :     CAmount min_viable_change{0};
     152                 :            :     /** Cost of creating the change output. */
     153                 :          0 :     CAmount m_change_fee{0};
     154                 :            :     /** Cost of creating the change output + cost of spending the change output in the future. */
     155                 :          0 :     CAmount m_cost_of_change{0};
     156                 :            :     /** The targeted feerate of the transaction being built. */
     157                 :            :     CFeeRate m_effective_feerate;
     158                 :            :     /** The feerate estimate used to estimate an upper bound on what should be sufficient to spend
     159                 :            :      * the change output sometime in the future. */
     160                 :            :     CFeeRate m_long_term_feerate;
     161                 :            :     /** If the cost to spend a change output at the discard feerate exceeds its value, drop it to fees. */
     162                 :            :     CFeeRate m_discard_feerate;
     163                 :            :     /** Size of the transaction before coin selection, consisting of the header and recipient
     164                 :            :      * output(s), excluding the inputs and change output(s). */
     165                 :          0 :     size_t tx_noinputs_size = 0;
     166                 :            :     /** Indicate that we are subtracting the fee from outputs */
     167                 :          0 :     bool m_subtract_fee_outputs = false;
     168                 :            :     /** When true, always spend all (up to OUTPUT_GROUP_MAX_ENTRIES) or none of the outputs
     169                 :            :      * associated with the same address. This helps reduce privacy leaks resulting from address
     170                 :            :      * reuse. Dust outputs are not eligible to be added to output groups and thus not considered. */
     171                 :          0 :     bool m_avoid_partial_spends = false;
     172                 :            :     /**
     173                 :            :      * When true, allow unsafe coins to be selected during Coin Selection. This may spend unconfirmed outputs:
     174                 :            :      * 1) Received from other wallets, 2) replacing other txs, 3) that have been replaced.
     175                 :            :      */
     176                 :          0 :     bool m_include_unsafe_inputs = false;
     177                 :            : 
     178                 :          0 :     CoinSelectionParams(FastRandomContext& rng_fast, size_t change_output_size, size_t change_spend_size,
     179                 :            :                         CAmount min_change_target, CFeeRate effective_feerate,
     180                 :            :                         CFeeRate long_term_feerate, CFeeRate discard_feerate, size_t tx_noinputs_size, bool avoid_partial)
     181                 :          0 :         : rng_fast{rng_fast},
     182                 :          0 :           change_output_size(change_output_size),
     183                 :          0 :           change_spend_size(change_spend_size),
     184                 :          0 :           m_min_change_target(min_change_target),
     185                 :          0 :           m_effective_feerate(effective_feerate),
     186                 :          0 :           m_long_term_feerate(long_term_feerate),
     187                 :          0 :           m_discard_feerate(discard_feerate),
     188                 :          0 :           tx_noinputs_size(tx_noinputs_size),
     189                 :          0 :           m_avoid_partial_spends(avoid_partial)
     190                 :            :     {
     191                 :          0 :     }
     192                 :          0 :     CoinSelectionParams(FastRandomContext& rng_fast)
     193                 :          0 :         : rng_fast{rng_fast} {}
     194                 :            : };
     195                 :            : 
     196                 :            : /** Parameters for filtering which OutputGroups we may use in coin selection.
     197                 :            :  * We start by being very selective and requiring multiple confirmations and
     198                 :            :  * then get more permissive if we cannot fund the transaction. */
     199                 :            : struct CoinEligibilityFilter
     200                 :            : {
     201                 :            :     /** Minimum number of confirmations for outputs that we sent to ourselves.
     202                 :            :      * We may use unconfirmed UTXOs sent from ourselves, e.g. change outputs. */
     203                 :            :     const int conf_mine;
     204                 :            :     /** Minimum number of confirmations for outputs received from a different wallet. */
     205                 :            :     const int conf_theirs;
     206                 :            :     /** Maximum number of unconfirmed ancestors aggregated across all UTXOs in an OutputGroup. */
     207                 :            :     const uint64_t max_ancestors;
     208                 :            :     /** Maximum number of descendants that a single UTXO in the OutputGroup may have. */
     209                 :            :     const uint64_t max_descendants;
     210                 :            :     /** When avoid_reuse=true and there are full groups (OUTPUT_GROUP_MAX_ENTRIES), whether or not to use any partial groups.*/
     211                 :          0 :     const bool m_include_partial_groups{false};
     212                 :            : 
     213                 :            :     CoinEligibilityFilter() = delete;
     214                 :          0 :     CoinEligibilityFilter(int conf_mine, int conf_theirs, uint64_t max_ancestors) : conf_mine(conf_mine), conf_theirs(conf_theirs), max_ancestors(max_ancestors), max_descendants(max_ancestors) {}
     215                 :          0 :     CoinEligibilityFilter(int conf_mine, int conf_theirs, uint64_t max_ancestors, uint64_t max_descendants) : conf_mine(conf_mine), conf_theirs(conf_theirs), max_ancestors(max_ancestors), max_descendants(max_descendants) {}
     216                 :          0 :     CoinEligibilityFilter(int conf_mine, int conf_theirs, uint64_t max_ancestors, uint64_t max_descendants, bool include_partial) : conf_mine(conf_mine), conf_theirs(conf_theirs), max_ancestors(max_ancestors), max_descendants(max_descendants), m_include_partial_groups(include_partial) {}
     217                 :            : 
     218                 :          0 :     bool operator<(const CoinEligibilityFilter& other) const {
     219                 :          0 :         return std::tie(conf_mine, conf_theirs, max_ancestors, max_descendants, m_include_partial_groups)
     220                 :          0 :                < std::tie(other.conf_mine, other.conf_theirs, other.max_ancestors, other.max_descendants, other.m_include_partial_groups);
     221                 :            :     }
     222                 :            : };
     223                 :            : 
     224                 :            : /** A group of UTXOs paid to the same output script. */
     225                 :            : struct OutputGroup
     226                 :            : {
     227                 :            :     /** The list of UTXOs contained in this output group. */
     228                 :            :     std::vector<std::shared_ptr<COutput>> m_outputs;
     229                 :            :     /** Whether the UTXOs were sent by the wallet to itself. This is relevant because we may want at
     230                 :            :      * least a certain number of confirmations on UTXOs received from outside wallets while trusting
     231                 :            :      * our own UTXOs more. */
     232                 :          0 :     bool m_from_me{true};
     233                 :            :     /** The total value of the UTXOs in sum. */
     234                 :          0 :     CAmount m_value{0};
     235                 :            :     /** The minimum number of confirmations the UTXOs in the group have. Unconfirmed is 0. */
     236                 :          0 :     int m_depth{999};
     237                 :            :     /** The aggregated count of unconfirmed ancestors of all UTXOs in this
     238                 :            :      * group. Not deduplicated and may overestimate when ancestors are shared. */
     239                 :          0 :     size_t m_ancestors{0};
     240                 :            :     /** The maximum count of descendants of a single UTXO in this output group. */
     241                 :          0 :     size_t m_descendants{0};
     242                 :            :     /** The value of the UTXOs after deducting the cost of spending them at the effective feerate. */
     243                 :          0 :     CAmount effective_value{0};
     244                 :            :     /** The fee to spend these UTXOs at the effective feerate. */
     245                 :          0 :     CAmount fee{0};
     246                 :            :     /** The fee to spend these UTXOs at the long term feerate. */
     247                 :          0 :     CAmount long_term_fee{0};
     248                 :            :     /** The feerate for spending a created change output eventually (i.e. not urgently, and thus at
     249                 :            :      * a lower feerate). Calculated using long term fee estimate. This is used to decide whether
     250                 :            :      * it could be economical to create a change output. */
     251                 :          0 :     CFeeRate m_long_term_feerate{0};
     252                 :            :     /** Indicate that we are subtracting the fee from outputs.
     253                 :            :      * When true, the value that is used for coin selection is the UTXO's real value rather than effective value */
     254                 :          0 :     bool m_subtract_fee_outputs{false};
     255                 :            :     /** Total weight of the UTXOs in this group. */
     256                 :          0 :     int m_weight{0};
     257                 :            : 
     258                 :          0 :     OutputGroup() {}
     259                 :          0 :     OutputGroup(const CoinSelectionParams& params) :
     260                 :          0 :         m_long_term_feerate(params.m_long_term_feerate),
     261                 :          0 :         m_subtract_fee_outputs(params.m_subtract_fee_outputs)
     262                 :          0 :     {}
     263                 :            : 
     264                 :            :     void Insert(const std::shared_ptr<COutput>& output, size_t ancestors, size_t descendants);
     265                 :            :     bool EligibleForSpending(const CoinEligibilityFilter& eligibility_filter) const;
     266                 :            :     CAmount GetSelectionAmount() const;
     267                 :            : };
     268                 :            : 
     269                 :          0 : struct Groups {
     270                 :            :     // Stores 'OutputGroup' containing only positive UTXOs (value > 0).
     271                 :            :     std::vector<OutputGroup> positive_group;
     272                 :            :     // Stores 'OutputGroup' which may contain both positive and negative UTXOs.
     273                 :            :     std::vector<OutputGroup> mixed_group;
     274                 :            : };
     275                 :            : 
     276                 :            : /** Stores several 'Groups' whose were mapped by output type. */
     277                 :          0 : struct OutputGroupTypeMap
     278                 :            : {
     279                 :            :     // Maps output type to output groups.
     280                 :            :     std::map<OutputType, Groups> groups_by_type;
     281                 :            :     // All inserted groups, no type distinction.
     282                 :            :     Groups all_groups;
     283                 :            : 
     284                 :            :     // Based on the insert flag; appends group to the 'mixed_group' and, if value > 0, to the 'positive_group'.
     285                 :            :     // This affects both; the groups filtered by type and the overall groups container.
     286                 :            :     void Push(const OutputGroup& group, OutputType type, bool insert_positive, bool insert_mixed);
     287                 :            :     // Different output types count
     288                 :          0 :     size_t TypesCount() { return groups_by_type.size(); }
     289                 :            : };
     290                 :            : 
     291                 :            : typedef std::map<CoinEligibilityFilter, OutputGroupTypeMap> FilteredOutputGroups;
     292                 :            : 
     293                 :            : /** Choose a random change target for each transaction to make it harder to fingerprint the Core
     294                 :            :  * wallet based on the change output values of transactions it creates.
     295                 :            :  * Change target covers at least change fees and adds a random value on top of it.
     296                 :            :  * The random value is between 50ksat and min(2 * payment_value, 1milsat)
     297                 :            :  * When payment_value <= 25ksat, the value is just 50ksat.
     298                 :            :  *
     299                 :            :  * Making change amounts similar to the payment value may help disguise which output(s) are payments
     300                 :            :  * are which ones are change. Using double the payment value may increase the number of inputs
     301                 :            :  * needed (and thus be more expensive in fees), but breaks analysis techniques which assume the
     302                 :            :  * coins selected are just sufficient to cover the payment amount ("unnecessary input" heuristic).
     303                 :            :  *
     304                 :            :  * @param[in]   payment_value   Average payment value of the transaction output(s).
     305                 :            :  * @param[in]   change_fee      Fee for creating a change output.
     306                 :            :  */
     307                 :            : [[nodiscard]] CAmount GenerateChangeTarget(const CAmount payment_value, const CAmount change_fee, FastRandomContext& rng);
     308                 :            : 
     309                 :            : enum class SelectionAlgorithm : uint8_t
     310                 :            : {
     311                 :            :     BNB = 0,
     312                 :            :     KNAPSACK = 1,
     313                 :            :     SRD = 2,
     314                 :            :     MANUAL = 3,
     315                 :            : };
     316                 :            : 
     317                 :            : std::string GetAlgorithmName(const SelectionAlgorithm algo);
     318                 :            : 
     319                 :            : struct SelectionResult
     320                 :            : {
     321                 :            : private:
     322                 :            :     /** Set of inputs selected by the algorithm to use in the transaction */
     323                 :            :     std::set<std::shared_ptr<COutput>> m_selected_inputs;
     324                 :            :     /** The target the algorithm selected for. Equal to the recipient amount plus non-input fees */
     325                 :            :     CAmount m_target;
     326                 :            :     /** The algorithm used to produce this result */
     327                 :            :     SelectionAlgorithm m_algo;
     328                 :            :     /** Whether the input values for calculations should be the effective value (true) or normal value (false) */
     329                 :          0 :     bool m_use_effective{false};
     330                 :            :     /** The computed waste */
     331                 :            :     std::optional<CAmount> m_waste;
     332                 :            :     /** Total weight of the selected inputs */
     333                 :          0 :     int m_weight{0};
     334                 :            :     /** How much individual inputs overestimated the bump fees for the shared ancestry */
     335                 :          0 :     CAmount bump_fee_group_discount{0};
     336                 :            : 
     337                 :            :     template<typename T>
     338                 :          0 :     void InsertInputs(const T& inputs)
     339                 :            :     {
     340                 :            :         // Store sum of combined input sets to check that the results have no shared UTXOs
     341                 :          0 :         const size_t expected_count = m_selected_inputs.size() + inputs.size();
     342                 :          0 :         util::insert(m_selected_inputs, inputs);
     343   [ #  #  #  # ]:          0 :         if (m_selected_inputs.size() != expected_count) {
     344   [ #  #  #  #  :          0 :             throw std::runtime_error(STR_INTERNAL_BUG("Shared UTXOs among selection results"));
          #  #  #  #  #  
          #  #  #  #  #  
                   #  # ]
     345                 :            :         }
     346                 :          0 :     }
     347                 :            : 
     348                 :            :     /** Compute the waste for this result given the cost of change
     349                 :            :      * and the opportunity cost of spending these inputs now vs in the future.
     350                 :            :      * If change exists, waste = change_cost + inputs * (effective_feerate - long_term_feerate)
     351                 :            :      * If no change, waste = excess + inputs * (effective_feerate - long_term_feerate)
     352                 :            :      * where excess = selected_effective_value - target
     353                 :            :      * change_cost = effective_feerate * change_output_size + long_term_feerate * change_spend_size
     354                 :            :      *
     355                 :            :      * @param[in] change_cost The cost of creating change and spending it in the future.
     356                 :            :      *                        Only used if there is change, in which case it must be positive.
     357                 :            :      *                        Must be 0 if there is no change.
     358                 :            :      * @param[in] target The amount targeted by the coin selection algorithm.
     359                 :            :      * @param[in] use_effective_value Whether to use the input's effective value (when true) or the real value (when false).
     360                 :            :      * @return The waste
     361                 :            :      */
     362                 :            :     [[nodiscard]] CAmount GetSelectionWaste(CAmount change_cost, CAmount target, bool use_effective_value = true);
     363                 :            : 
     364                 :            : public:
     365                 :          0 :     explicit SelectionResult(const CAmount target, SelectionAlgorithm algo)
     366                 :          0 :         : m_target(target), m_algo(algo) {}
     367                 :            : 
     368                 :            :     SelectionResult() = delete;
     369                 :            : 
     370                 :            :     /** Get the sum of the input values */
     371                 :            :     [[nodiscard]] CAmount GetSelectedValue() const;
     372                 :            : 
     373                 :            :     [[nodiscard]] CAmount GetSelectedEffectiveValue() const;
     374                 :            : 
     375                 :            :     [[nodiscard]] CAmount GetTotalBumpFees() const;
     376                 :            : 
     377                 :            :     void Clear();
     378                 :            : 
     379                 :            :     void AddInput(const OutputGroup& group);
     380                 :            :     void AddInputs(const std::set<std::shared_ptr<COutput>>& inputs, bool subtract_fee_outputs);
     381                 :            : 
     382                 :            :     /** How much individual inputs overestimated the bump fees for shared ancestries */
     383                 :            :     void SetBumpFeeDiscount(const CAmount discount);
     384                 :            : 
     385                 :            :     /** Calculates and stores the waste for this selection via GetSelectionWaste */
     386                 :            :     void ComputeAndSetWaste(const CAmount min_viable_change, const CAmount change_cost, const CAmount change_fee);
     387                 :            :     [[nodiscard]] CAmount GetWaste() const;
     388                 :            : 
     389                 :            :     /**
     390                 :            :      * Combines the @param[in] other selection result into 'this' selection result.
     391                 :            :      *
     392                 :            :      * Important note:
     393                 :            :      * There must be no shared 'COutput' among the two selection results being combined.
     394                 :            :      */
     395                 :            :     void Merge(const SelectionResult& other);
     396                 :            : 
     397                 :            :     /** Get m_selected_inputs */
     398                 :            :     const std::set<std::shared_ptr<COutput>>& GetInputSet() const;
     399                 :            :     /** Get the vector of COutputs that will be used to fill in a CTransaction's vin */
     400                 :            :     std::vector<std::shared_ptr<COutput>> GetShuffledInputVector() const;
     401                 :            : 
     402                 :            :     bool operator<(SelectionResult other) const;
     403                 :            : 
     404                 :            :     /** Get the amount for the change output after paying needed fees.
     405                 :            :      *
     406                 :            :      * The change amount is not 100% precise due to discrepancies in fee calculation.
     407                 :            :      * The final change amount (if any) should be corrected after calculating the final tx fees.
     408                 :            :      * When there is a discrepancy, most of the time the final change would be slightly bigger than estimated.
     409                 :            :      *
     410                 :            :      * Following are the possible factors of discrepancy:
     411                 :            :      *  + non-input fees always include segwit flags
     412                 :            :      *  + input fee estimation always include segwit stack size
     413                 :            :      *  + input fees are rounded individually and not collectively, which leads to small rounding errors
     414                 :            :      *  - input counter size is always assumed to be 1vbyte
     415                 :            :      *
     416                 :            :      * @param[in]  min_viable_change  Minimum amount for change output, if change would be less then we forgo change
     417                 :            :      * @param[in]  change_fee         Fees to include change output in the tx
     418                 :            :      * @returns Amount for change output, 0 when there is no change.
     419                 :            :      *
     420                 :            :      */
     421                 :            :     CAmount GetChange(const CAmount min_viable_change, const CAmount change_fee) const;
     422                 :            : 
     423                 :          0 :     CAmount GetTarget() const { return m_target; }
     424                 :            : 
     425                 :            :     SelectionAlgorithm GetAlgo() const { return m_algo; }
     426                 :            : 
     427                 :          0 :     int GetWeight() const { return m_weight; }
     428                 :            : };
     429                 :            : 
     430                 :            : util::Result<SelectionResult> SelectCoinsBnB(std::vector<OutputGroup>& utxo_pool, const CAmount& selection_target, const CAmount& cost_of_change,
     431                 :            :                                              int max_weight);
     432                 :            : 
     433                 :            : /** Select coins by Single Random Draw. OutputGroups are selected randomly from the eligible
     434                 :            :  * outputs until the target is satisfied
     435                 :            :  *
     436                 :            :  * @param[in]  utxo_pool    The positive effective value OutputGroups eligible for selection
     437                 :            :  * @param[in]  target_value The target value to select for
     438                 :            :  * @param[in]  rng The randomness source to shuffle coins
     439                 :            :  * @param[in]  max_weight The maximum allowed weight for a selection result to be valid
     440                 :            :  * @returns If successful, a valid SelectionResult, otherwise, util::Error
     441                 :            :  */
     442                 :            : util::Result<SelectionResult> SelectCoinsSRD(const std::vector<OutputGroup>& utxo_pool, CAmount target_value, CAmount change_fee, FastRandomContext& rng,
     443                 :            :                                              int max_weight);
     444                 :            : 
     445                 :            : // Original coin selection algorithm as a fallback
     446                 :            : util::Result<SelectionResult> KnapsackSolver(std::vector<OutputGroup>& groups, const CAmount& nTargetValue,
     447                 :            :                                              CAmount change_target, FastRandomContext& rng, int max_weight);
     448                 :            : } // namespace wallet
     449                 :            : 
     450                 :            : #endif // BITCOIN_WALLET_COINSELECTION_H

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