def make_tx(self,
coins,
outputs,
change_addrs,
fee_estimator,
dust_threshold,
sign_schnorr=False):
'''Select unspent coins to spend to pay outputs. If the change is
greater than dust_threshold (after adding the change output to
the transaction) it is kept, otherwise none is sent and it is
added to the transaction fee.'''
# Deterministic randomness from coins
utxos = [c['prevout_hash'] + str(c['prevout_n']) for c in coins]
self.p = PRNG(''.join(sorted(utxos)))
# Copy the outputs so when adding change we don't modify "outputs"
tx = Transaction.from_io([], outputs, sign_schnorr=sign_schnorr)
# Size of the transaction with no inputs and no change
base_size = tx.estimated_size()
spent_amount = tx.output_value()
def sufficient_funds(buckets):
'''Given a list of buckets, return True if it has enough
value to pay for the transaction'''
total_input = sum(bucket.value for bucket in buckets)
total_size = sum(bucket.size for bucket in buckets) + base_size
return total_input >= spent_amount + fee_estimator(total_size)
# Collect the coins into buckets, choose a subset of the buckets
buckets = self.bucketize_coins(coins, sign_schnorr=sign_schnorr)
buckets = self.choose_buckets(buckets, sufficient_funds,
self.penalty_func(tx))
tx.add_inputs([coin for b in buckets for coin in b.coins])
tx_size = base_size + sum(bucket.size for bucket in buckets)
# This takes a count of change outputs and returns a tx fee;
# each pay-to-bitcoin-address output serializes as 34 bytes
fee = lambda count: fee_estimator(tx_size + count * 34)
change, dust = self.change_outputs(tx, change_addrs, fee,
dust_threshold)
tx.add_outputs(change)
tx.ephemeral['dust_to_fee'] = dust
self.print_error("using %d inputs" % len(tx.inputs()))
self.print_error("using buckets:", [bucket.desc for bucket in buckets])
return tx