How a wallet chooses which coins to spend

1001    m_target += other.m_target;
1002    m_use_effective |= other.m_use_effective;
1003    if (m_algo == SelectionAlgorithm::MANUAL) {
1004        m_algo = other.m_algo;
1005    }
1006
1007    m_weight += other.m_weight;
1008}
1009
1010const OutputSet& SelectionResult::GetInputSet() const
1011{
1012    return m_selected_inputs;
1013}
1014
1015std::vector<std::shared_ptr<COutput>> SelectionResult::GetShuffledInputVector() const
1016{
1017    std::vector<std::shared_ptr<COutput>> coins(m_selected_inputs.begin(), m_selected_inputs.end());
1018    std::shuffle(coins.begin(), coins.end(), FastRandomContext());
1019    return coins;
1020}
1021
1022bool SelectionResult::operator<(SelectionResult other) const
1023{
1024    Assert(m_waste.has_value());
1025    Assert(other.m_waste.has_value());
1026    // As this operator is only used in std::min_element, we want the result that has more inputs when waste are equal.
1027    return *m_waste < *other.m_waste || (*m_waste == *other.m_waste && m_selected_inputs.size() > other.m_selected_inputs.size());
1028}
1029
1030std::string GetAlgorithmName(const SelectionAlgorithm algo)
1031{
1032    switch (algo)
1033    {
1034    case SelectionAlgorithm::BNB: return "bnb";
1035    case SelectionAlgorithm::KNAPSACK: return "knapsack";
1036    case SelectionAlgorithm::SRD: return "srd";
1037    case SelectionAlgorithm::CG: return "cg";
1038    case SelectionAlgorithm::MANUAL: return "manual";
1039    } // no default case, so the compiler can warn about missing cases
1040    assert(false);
1041}
1042
1043CAmount SelectionResult::GetChange(const CAmount min_viable_change, const CAmount change_fee) const
1044{
1045    // change = SUM(inputs) - SUM(outputs) - fees
1046    // 1) With SFFO we don't pay any fees
1047    // 2) Otherwise we pay all the fees:
1048    //  - input fees are covered by GetSelectedEffectiveValue()
1049    //  - non_input_fee is included in m_target
1050    //  - change_fee
1051    const CAmount change = m_use_effective
1052                           ? GetSelectedEffectiveValue() - m_target - change_fee
1053                           : GetSelectedValue() - m_target;
1054
1055    if (change < min_viable_change) {
1056        return 0;
1057    }
1058
1059    return change;
1060}
1061
1062} // namespace wallet
1063