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#!/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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