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author | S3RK <1466284+S3RK@users.noreply.github.com> | 2022-07-13 08:54:44 +0200 |
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committer | S3RK <1466284+S3RK@users.noreply.github.com> | 2022-08-15 09:35:20 +0200 |
commit | 87e0ef903133492e76b7c7556209554d4a0c3d66 (patch) | |
tree | 461cbbcfe736286a16de1898d648e2cc61ffd8da | |
parent | 15e97a6886902ebb378829993a972dc52558aa92 (diff) | |
download | bitcoin-87e0ef903133492e76b7c7556209554d4a0c3d66.tar.xz |
wallet: use GetChange() in tx building
-rw-r--r-- | src/wallet/spend.cpp | 66 |
1 files changed, 22 insertions, 44 deletions
diff --git a/src/wallet/spend.cpp b/src/wallet/spend.cpp index d1fa3dbcb6..f9429907cd 100644 --- a/src/wallet/spend.cpp +++ b/src/wallet/spend.cpp @@ -902,23 +902,20 @@ static util::Result<CreatedTransactionResult> CreateTransactionInternal( } TRACE5(coin_selection, selected_coins, wallet.GetName().c_str(), GetAlgorithmName(result->GetAlgo()).c_str(), result->GetTarget(), result->GetWaste(), result->GetSelectedValue()); - // Always make a change output - // We will reduce the fee from this change output later, and remove the output if it is too small. - const CAmount change_and_fee = result->GetSelectedValue() - recipients_sum; - assert(change_and_fee >= 0); - CTxOut newTxOut(change_and_fee, scriptChange); - - if (nChangePosInOut == -1) { - // Insert change txn at random position: - nChangePosInOut = rng_fast.randrange(txNew.vout.size() + 1); - } - else if ((unsigned int)nChangePosInOut > txNew.vout.size()) { - return util::Error{_("Transaction change output index out of range")}; + const CAmount change_amount = result->GetChange(coin_selection_params.min_viable_change, coin_selection_params.m_change_fee); + if (change_amount > 0) { + CTxOut newTxOut(change_amount, scriptChange); + if (nChangePosInOut == -1) { + // Insert change txn at random position: + nChangePosInOut = rng_fast.randrange(txNew.vout.size() + 1); + } else if ((unsigned int)nChangePosInOut > txNew.vout.size()) { + return util::Error{_("Transaction change output index out of range")}; + } + txNew.vout.insert(txNew.vout.begin() + nChangePosInOut, newTxOut); + } else { + nChangePosInOut = -1; } - assert(nChangePosInOut != -1); - auto change_position = txNew.vout.insert(txNew.vout.begin() + nChangePosInOut, newTxOut); - // Shuffle selected coins and fill in final vin std::vector<COutput> selected_coins = result->GetShuffledInputVector(); @@ -942,42 +939,23 @@ static util::Result<CreatedTransactionResult> CreateTransactionInternal( if (nBytes == -1) { return util::Error{_("Missing solving data for estimating transaction size")}; } - nFeeRet = coin_selection_params.m_effective_feerate.GetFee(nBytes); - - // Subtract fee from the change output if not subtracting it from recipient outputs - CAmount fee_needed = nFeeRet; - if (!coin_selection_params.m_subtract_fee_outputs) { - change_position->nValue -= fee_needed; - } - - // We want to drop the change to fees if: - // 1. The change output would be dust - // 2. The change is within the (almost) exact match window, i.e. it is less than or equal to the cost of the change output (cost_of_change) - CAmount change_amount = change_position->nValue; - if (IsDust(*change_position, coin_selection_params.m_discard_feerate) || change_amount <= coin_selection_params.m_cost_of_change) - { - nChangePosInOut = -1; - change_amount = 0; - txNew.vout.erase(change_position); + CAmount fee_needed = coin_selection_params.m_effective_feerate.GetFee(nBytes); + nFeeRet = result->GetSelectedValue() - recipients_sum - change_amount; - // Because we have dropped this change, the tx size and required fee will be different, so let's recalculate those - tx_sizes = CalculateMaximumSignedTxSize(CTransaction(txNew), &wallet, &coin_control); - nBytes = tx_sizes.vsize; - fee_needed = coin_selection_params.m_effective_feerate.GetFee(nBytes); - } - - // The only time that fee_needed should be less than the amount available for fees (in change_and_fee - change_amount) is when + // The only time that fee_needed should be less than the amount available for fees is when // we are subtracting the fee from the outputs. If this occurs at any other time, it is a bug. - assert(coin_selection_params.m_subtract_fee_outputs || fee_needed <= change_and_fee - change_amount); + assert(coin_selection_params.m_subtract_fee_outputs || fee_needed <= nFeeRet); - // Update nFeeRet in case fee_needed changed due to dropping the change output - if (fee_needed <= change_and_fee - change_amount) { - nFeeRet = change_and_fee - change_amount; + // If there is a change output and we overpay the fees then increase the change to match the fee needed + if (nChangePosInOut != -1 && fee_needed < nFeeRet) { + auto& change = txNew.vout.at(nChangePosInOut); + change.nValue += nFeeRet - fee_needed; + nFeeRet = fee_needed; } // Reduce output values for subtractFeeFromAmount if (coin_selection_params.m_subtract_fee_outputs) { - CAmount to_reduce = fee_needed + change_amount - change_and_fee; + CAmount to_reduce = fee_needed - nFeeRet; int i = 0; bool fFirst = true; for (const auto& recipient : vecSend) |