tMerge pull request #3351 from SomberNight/segwit_tx_size_estimation - electrum - Electrum Bitcoin wallet
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---
DIR commit ac5cbdaca2a6ed144550dbc97593fdd0058d3d01
DIR parent 8a200aaf33711c728665b6cfb0c519d05c419848
HTML Author: ThomasV <thomasv@electrum.org>
Date: Thu, 23 Nov 2017 09:41:02 +0100
Merge pull request #3351 from SomberNight/segwit_tx_size_estimation
better segwit tx size estimation
Diffstat:
M lib/coinchooser.py | 3 ++-
M lib/transaction.py | 37 ++++++++++++++++++++++---------
2 files changed, 29 insertions(+), 11 deletions(-)
---
DIR diff --git a/lib/coinchooser.py b/lib/coinchooser.py
t@@ -91,8 +91,9 @@ class CoinChooserBase(PrintError):
buckets[key].append(coin)
def make_Bucket(desc, coins):
- size = sum(Transaction.estimated_input_size(coin)
+ weight = sum(Transaction.estimated_input_weight(coin)
for coin in coins)
+ size = Transaction.virtual_size_from_weight(weight)
value = sum(coin['value'] for coin in coins)
return Bucket(desc, size, value, coins)
DIR diff --git a/lib/transaction.py b/lib/transaction.py
t@@ -635,11 +635,11 @@ class Transaction:
return pk_list, sig_list
@classmethod
- def serialize_witness(self, txin):
+ def serialize_witness(self, txin, estimate_size=False):
add_w = lambda x: var_int(len(x)//2) + x
if not self.is_segwit_input(txin):
return '00'
- pubkeys, sig_list = self.get_siglist(txin)
+ pubkeys, sig_list = self.get_siglist(txin, estimate_size)
if txin['type'] in ['p2wpkh', 'p2wpkh-p2sh']:
witness = var_int(2) + add_w(sig_list[0]) + add_w(pubkeys[0])
elif txin['type'] in ['p2wsh', 'p2wsh-p2sh']:
t@@ -648,7 +648,10 @@ class Transaction:
witness = var_int(n) + '00' + ''.join(add_w(x) for x in sig_list) + add_w(witness_script)
else:
raise BaseException('wrong txin type')
- value_field = '' if self.is_txin_complete(txin) else var_int(0xffffffff) + int_to_hex(txin['value'], 8)
+ if self.is_txin_complete(txin) or estimate_size:
+ value_field = ''
+ else:
+ value_field = var_int(0xffffffff) + int_to_hex(txin['value'], 8)
return value_field + witness
@classmethod
t@@ -781,7 +784,7 @@ class Transaction:
if witness and self.is_segwit():
marker = '00'
flag = '01'
- witness = ''.join(self.serialize_witness(x) for x in inputs)
+ witness = ''.join(self.serialize_witness(x, estimate_size) for x in inputs)
return nVersion + marker + flag + txins + txouts + witness + nLocktime
else:
return nVersion + txins + txouts + nLocktime
t@@ -830,13 +833,26 @@ class Transaction:
weights, but for simplicity we approximate that with (virtual_size)x4
"""
weight = self.estimated_weight()
- return weight // 4 + (weight % 4 > 0)
+ return self.virtual_size_from_weight(weight)
+
+ @classmethod
+ def estimated_input_weight(cls, txin):
+ '''Return an estimate of serialized input weight in weight units.'''
+ script = cls.input_script(txin, True)
+ input_size = len(cls.serialize_input(txin, script)) // 2
+
+ # note: we should actually branch based on tx.is_segwit()
+ # only if none of the inputs have a witness, is the size actually 0
+ if cls.is_segwit_input(txin):
+ witness_size = len(cls.serialize_witness(txin, True)) // 2
+ else:
+ witness_size = 0
+
+ return 4 * input_size + witness_size
@classmethod
- def estimated_input_size(self, txin):
- '''Return an estimated of serialized input size in bytes.'''
- script = self.input_script(txin, True)
- return len(self.serialize_input(txin, script)) // 2
+ def virtual_size_from_weight(cls, weight):
+ return weight // 4 + (weight % 4 > 0)
def estimated_total_size(self):
"""Return an estimated total transaction size in bytes."""
t@@ -847,7 +863,8 @@ class Transaction:
if not self.is_segwit():
return 0
inputs = self.inputs()
- witness = ''.join(self.serialize_witness(x) for x in inputs)
+ estimate = not self.is_complete()
+ witness = ''.join(self.serialize_witness(x, estimate) for x in inputs)
witness_size = len(witness) // 2 + 2 # include marker and flag
return witness_size