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test: introduce and use calculate_input_weight helper

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Rather than manually estimating an input's weight by adding up all the
involved components (fixed-size skeleton, compact-serialized lengths,
and the actual scriptSig / witness stack items) we can simply take use
of the serialization classes `CTxIn` / `CTxInWitness` instead, to
achieve the same with significantly less code.

The new helper is used in the functional tests rpc_psbt.py and
wallet_send.py, where the previous manual estimation code was
duplicated.
This commit is contained in:
Sebastian Falbesoner
2024-04-01 14:03:35 +02:00
parent 61de64df67
commit f81fad5e0f
3 changed files with 29 additions and 29 deletions
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17
test/functional/rpc_psbt.py
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@ -16,8 +16,6 @@ from test_framework.messages import (
CTxIn,
CTxOut,
MAX_BIP125_RBF_SEQUENCE,
WITNESS_SCALE_FACTOR,
ser_compact_size,
)
from test_framework.psbt import (
PSBT,
@ -42,6 +40,7 @@ from test_framework.util import (
find_vout_for_address,
)
from test_framework.wallet_util import (
calculate_input_weight,
generate_keypair,
get_generate_key,
)
@ -752,17 +751,9 @@ class PSBTTest(BitcoinTestFramework):
input_idx = i
break
psbt_in = dec["inputs"][input_idx]
# Calculate the input weight
# (prevout + sequence + length of scriptSig + scriptsig) * WITNESS_SCALE_FACTOR + len of num scriptWitness stack items + (length of stack item + stack item) * N stack items
# Note that occasionally this weight estimate may be slightly larger or smaller than the real weight
# as sometimes ECDSA signatures are one byte shorter than expected with a probability of 1/128
len_scriptsig = len(psbt_in["final_scriptSig"]["hex"]) // 2 if "final_scriptSig" in psbt_in else 0
len_scriptsig += len(ser_compact_size(len_scriptsig))
len_scriptwitness = (sum([(len(x) // 2) + len(ser_compact_size(len(x) // 2)) for x in psbt_in["final_scriptwitness"]]) + len(ser_compact_size(len(psbt_in["final_scriptwitness"])))) if "final_scriptwitness" in psbt_in else 0
len_prevout_txid = 32
len_prevout_index = 4
len_sequence = 4
input_weight = ((len_prevout_txid + len_prevout_index + len_sequence + len_scriptsig) * WITNESS_SCALE_FACTOR) + len_scriptwitness
scriptsig_hex = psbt_in["final_scriptSig"]["hex"] if "final_scriptSig" in psbt_in else ""
witness_stack_hex = psbt_in["final_scriptwitness"] if "final_scriptwitness" in psbt_in else None
input_weight = calculate_input_weight(scriptsig_hex, witness_stack_hex)
low_input_weight = input_weight // 2
high_input_weight = input_weight * 2