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26 lines
1.3 KiB
26 lines
1.3 KiB
5 years ago
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#!/usr/bin/env python3
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# Copyright (c) 2019 The Bitcoin Core developers
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# Distributed under the MIT software license, see the accompanying
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# file COPYING or http://www.opensource.org/licenses/mit-license.php.
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"""Useful Script constants and utils."""
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from test_framework.script import CScript
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# To prevent a "tx-size-small" policy rule error, a transaction has to have a
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# non-witness size of at least 82 bytes (MIN_STANDARD_TX_NONWITNESS_SIZE in
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# src/policy/policy.h). Considering a Tx with the smallest possible single
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# input (blank, empty scriptSig), and with an output omitting the scriptPubKey,
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# we get to a minimum size of 60 bytes:
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#
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# Tx Skeleton: 4 [Version] + 1 [InCount] + 1 [OutCount] + 4 [LockTime] = 10 bytes
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# Blank Input: 32 [PrevTxHash] + 4 [Index] + 1 [scriptSigLen] + 4 [SeqNo] = 41 bytes
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# Output: 8 [Amount] + 1 [scriptPubKeyLen] = 9 bytes
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#
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# Hence, the scriptPubKey of the single output has to have a size of at
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# least 22 bytes, which corresponds to the size of a P2WPKH scriptPubKey.
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# The following script constant consists of a single push of 21 bytes of 'a':
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# <PUSH_21> <21-bytes of 'a'>
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# resulting in a 22-byte size. It should be used whenever (small) fake
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# scriptPubKeys are needed, to guarantee that the minimum transaction size is
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# met.
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DUMMY_P2WPKH_SCRIPT = CScript([b'a' * 21])
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