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#!/usr/bin/env python3
# Copyright (c) 2019-2020 The Bitcoin Core developers
# Distributed under the MIT software license, see the accompanying
# file COPYING or http://www.opensource.org/licenses/mit-license.php.
"""Useful Script constants and utils."""
from test_framework.script import CScript, hash160, sha256, OP_0, OP_DUP, OP_HASH160, OP_CHECKSIG, OP_EQUAL, OP_EQUALVERIFY
# To prevent a "tx-size-small" policy rule error, a transaction has to have a
# non-witness size of at least 82 bytes (MIN_STANDARD_TX_NONWITNESS_SIZE in
# src/policy/policy.h). Considering a Tx with the smallest possible single
# input (blank, empty scriptSig), and with an output omitting the scriptPubKey,
# we get to a minimum size of 60 bytes:
#
# Tx Skeleton: 4 [Version] + 1 [InCount] + 1 [OutCount] + 4 [LockTime] = 10 bytes
# Blank Input: 32 [PrevTxHash] + 4 [Index] + 1 [scriptSigLen] + 4 [SeqNo] = 41 bytes
# Output: 8 [Amount] + 1 [scriptPubKeyLen] = 9 bytes
#
# Hence, the scriptPubKey of the single output has to have a size of at
# least 22 bytes, which corresponds to the size of a P2WPKH scriptPubKey.
# The following script constant consists of a single push of 21 bytes of 'a':
# <PUSH_21> <21-bytes of 'a'>
# resulting in a 22-byte size. It should be used whenever (small) fake
# scriptPubKeys are needed, to guarantee that the minimum transaction size is
# met.
DUMMY_P2WPKH_SCRIPT = CScript([b'a' * 21])
DUMMY_2_P2WPKH_SCRIPT = CScript([b'b' * 21])
def keyhash_to_p2pkh_script(hash, main = False):
assert len(hash) == 20
return CScript([OP_DUP, OP_HASH160, hash, OP_EQUALVERIFY, OP_CHECKSIG])
def scripthash_to_p2sh_script(hash, main = False):
assert len(hash) == 20
return CScript([OP_HASH160, hash, OP_EQUAL])
def key_to_p2pkh_script(key, main = False):
key = check_key(key)
return keyhash_to_p2pkh_script(hash160(key), main)
def script_to_p2sh_script(script, main = False):
script = check_script(script)
return scripthash_to_p2sh_script(hash160(script), main)
def key_to_p2sh_p2wpkh_script(key, main = False):
key = check_key(key)
p2shscript = CScript([OP_0, hash160(key)])
return script_to_p2sh_script(p2shscript, main)
def program_to_witness_script(version, program, main = False):
if isinstance(program, str):
program = bytes.fromhex(program)
assert 0 <= version <= 16
assert 2 <= len(program) <= 40
assert version > 0 or len(program) in [20, 32]
return CScript([version, program])
def script_to_p2wsh_script(script, main = False):
script = check_script(script)
return program_to_witness_script(0, sha256(script), main)
def key_to_p2wpkh_script(key, main = False):
key = check_key(key)
return program_to_witness_script(0, hash160(key), main)
def script_to_p2sh_p2wsh_script(script, main = False):
script = check_script(script)
p2shscript = CScript([OP_0, sha256(script)])
return script_to_p2sh_script(p2shscript, main)
def check_key(key):
if isinstance(key, str):
key = bytes.fromhex(key) # Assuming this is hex string
if isinstance(key, bytes) and (len(key) == 33 or len(key) == 65):
return key
assert False
def check_script(script):
if isinstance(script, str):
script = bytes.fromhex(script) # Assuming this is hex string
if isinstance(script, bytes) or isinstance(script, CScript):
return script
assert False
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