7ac618d339
TxFee calculates pre-HF4 fees as sum(inputs) - sum(outputs) with overflow detection. Coinbase transactions return zero fee. Co-Authored-By: Charon <charon@lethean.io>
79 lines
1.8 KiB
Go
79 lines
1.8 KiB
Go
// Copyright (c) 2017-2026 Lethean (https://lt.hn)
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//
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// Licensed under the European Union Public Licence (EUPL) version 1.2.
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// SPDX-License-Identifier: EUPL-1.2
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package consensus
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import (
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"fmt"
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"math"
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"forge.lthn.ai/core/go-blockchain/types"
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)
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// TxFee calculates the transaction fee for pre-HF4 (v0/v1) transactions.
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// Coinbase transactions return 0. For standard transactions, fee equals
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// the difference between total input amounts and total output amounts.
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func TxFee(tx *types.Transaction) (uint64, error) {
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if isCoinbase(tx) {
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return 0, nil
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}
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inputSum, err := sumInputs(tx)
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if err != nil {
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return 0, err
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}
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outputSum, err := sumOutputs(tx)
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if err != nil {
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return 0, err
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}
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if outputSum > inputSum {
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return 0, fmt.Errorf("%w: inputs=%d, outputs=%d", ErrNegativeFee, inputSum, outputSum)
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}
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return inputSum - outputSum, nil
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}
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// isCoinbase returns true if the transaction's first input is TxInputGenesis.
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func isCoinbase(tx *types.Transaction) bool {
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if len(tx.Vin) == 0 {
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return false
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}
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_, ok := tx.Vin[0].(types.TxInputGenesis)
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return ok
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}
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// sumInputs totals all TxInputToKey amounts, checking for overflow.
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func sumInputs(tx *types.Transaction) (uint64, error) {
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var total uint64
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for _, vin := range tx.Vin {
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toKey, ok := vin.(types.TxInputToKey)
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if !ok {
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continue
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}
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if total > math.MaxUint64-toKey.Amount {
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return 0, ErrInputOverflow
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}
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total += toKey.Amount
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}
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return total, nil
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}
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// sumOutputs totals all TxOutputBare amounts, checking for overflow.
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func sumOutputs(tx *types.Transaction) (uint64, error) {
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var total uint64
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for _, vout := range tx.Vout {
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bare, ok := vout.(types.TxOutputBare)
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if !ok {
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continue
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}
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if total > math.MaxUint64-bare.Amount {
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return 0, ErrOutputOverflow
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}
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total += bare.Amount
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}
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return total, nil
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}
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