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https://github.com/LBRYFoundation/LBRY-Vault.git
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93bb09230c
This has several advantages. Fee calculation is now very fast, as we don't need to keep reserializing the tx. Another is that we can reason about the fees after adding a change output without having to add it, recalculate the tx fee, and remove it again.
76 lines
2.8 KiB
Python
76 lines
2.8 KiB
Python
#!/usr/bin/env python
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#
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# Electrum - lightweight Bitcoin client
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# Copyright (C) 2011 thomasv@gitorious
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#
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# This program is free software: you can redistribute it and/or modify
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# it under the terms of the GNU General Public License as published by
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# the Free Software Foundation, either version 3 of the License, or
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# (at your option) any later version.
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#
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# This program is distributed in the hope that it will be useful,
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# but WITHOUT ANY WARRANTY; without even the implied warranty of
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# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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# GNU General Public License for more details.
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#
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# You should have received a copy of the GNU General Public License
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# along with this program. If not, see <http://www.gnu.org/licenses/>.
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from operator import itemgetter
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from util import NotEnoughFunds, PrintError, profiler
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from transaction import Transaction
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class CoinChooser(PrintError):
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def make_tx(self, coins, outputs, change_addrs, fee_estimator,
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dust_threshold):
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'''Select unspent coins to spend to pay outputs. If the change is
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greater than dust_threshold (after adding the change output to
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the transaction) it is kept, otherwise none is sent and it is
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added to the transaction fee.'''
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amount = sum(map(lambda x: x[2], outputs))
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total = 0
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tx = Transaction.from_io([], outputs)
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# Size of the transaction with no inputs and no change
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base_size = tx.estimated_size()
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# Pay to bitcoin address serializes as 34 bytes
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change_size = 34
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# Size of each serialized coin
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for coin in coins:
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coin['size'] = Transaction.estimated_input_size(coin)
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size = base_size
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# add inputs, sorted by age
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for item in coins:
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v = item.get('value')
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total += v
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size += item['size']
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tx.add_input(item)
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if total >= amount + fee_estimator(size):
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break
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else:
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raise NotEnoughFunds()
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# remove unneeded inputs.
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for item in sorted(tx.inputs, key=itemgetter('value')):
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v = item.get('value')
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if total - v >= amount + fee_estimator(size - item['size']):
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tx.inputs.remove(item)
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total -= v
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size -= item['size']
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self.print_error("using %d inputs" % len(tx.inputs))
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# If change is above dust threshold after accounting for the
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# size of the change output, add it to the transaction.
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change_amount = total - (amount + fee_estimator(size + change_size))
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if change_amount > dust_threshold:
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tx.outputs.append(('address', change_addrs[0], change_amount))
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size += change_size
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self.print_error('change', change_amount)
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elif change_amount:
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self.print_error('not keeping dust', change_amount)
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return tx
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