mirror of
https://github.com/mempool/mempool.git
synced 2025-01-07 14:09:16 +01:00
69 lines
2.8 KiB
TypeScript
69 lines
2.8 KiB
TypeScript
import { Transaction, Vin } from './interfaces/electrs.interface';
|
|
|
|
const P2SH_P2WPKH_COST = 21 * 4; // the WU cost for the non-witness part of P2SH-P2WPKH
|
|
const P2SH_P2WSH_COST = 35 * 4; // the WU cost for the non-witness part of P2SH-P2WSH
|
|
|
|
export function calcSegwitFeeGains(tx: Transaction) {
|
|
// calculated in weight units
|
|
let realizedGains = 0;
|
|
let potentialBech32Gains = 0;
|
|
let potentialP2shGains = 0;
|
|
|
|
for (const vin of tx.vin) {
|
|
if (!vin.prevout) { continue; }
|
|
|
|
const isP2pkh = vin.prevout.scriptpubkey_type === 'p2pkh';
|
|
const isP2sh = vin.prevout.scriptpubkey_type === 'p2sh';
|
|
const isP2wsh = vin.prevout.scriptpubkey_type === 'v0_p2wsh';
|
|
const isP2wpkh = vin.prevout.scriptpubkey_type === 'v0_p2wpkh';
|
|
|
|
const op = vin.scriptsig ? vin.scriptsig_asm.split(' ')[0] : null;
|
|
const isP2sh2Wpkh = isP2sh && !!vin.witness && op === 'OP_PUSHBYTES_22';
|
|
const isP2sh2Wsh = isP2sh && !!vin.witness && op === 'OP_PUSHBYTES_34';
|
|
|
|
switch (true) {
|
|
// Native Segwit - P2WPKH/P2WSH (Bech32)
|
|
case isP2wpkh:
|
|
case isP2wsh:
|
|
// maximal gains: the scriptSig is moved entirely to the witness part
|
|
realizedGains += witnessSize(vin) * 3;
|
|
// XXX P2WSH output creation is more expensive, should we take this into consideration?
|
|
break;
|
|
|
|
// Backward compatible Segwit - P2SH-P2WPKH
|
|
case isP2sh2Wpkh:
|
|
// the scriptSig is moved to the witness, but we have extra 21 extra non-witness bytes (48 WU)
|
|
realizedGains += witnessSize(vin) * 3 - P2SH_P2WPKH_COST;
|
|
potentialBech32Gains += P2SH_P2WPKH_COST;
|
|
break;
|
|
|
|
// Backward compatible Segwit - P2SH-P2WSH
|
|
case isP2sh2Wsh:
|
|
// the scriptSig is moved to the witness, but we have extra 35 extra non-witness bytes
|
|
realizedGains += witnessSize(vin) * 3 - P2SH_P2WSH_COST;
|
|
potentialBech32Gains += P2SH_P2WSH_COST;
|
|
break;
|
|
|
|
// Non-segwit P2PKH/P2SH
|
|
case isP2pkh:
|
|
case isP2sh:
|
|
const fullGains = scriptSigSize(vin) * 3;
|
|
potentialBech32Gains += fullGains;
|
|
potentialP2shGains += fullGains - (isP2pkh ? P2SH_P2WPKH_COST : P2SH_P2WSH_COST);
|
|
break;
|
|
|
|
// TODO: should we also consider P2PK and pay-to-bare-script (non-p2sh-wrapped) as upgradable to P2WPKH and P2WSH?
|
|
}
|
|
}
|
|
|
|
// returned as percentage of the total tx weight
|
|
return { realizedGains: realizedGains / (tx.weight + realizedGains) // percent of the pre-segwit tx size
|
|
, potentialBech32Gains: potentialBech32Gains / tx.weight
|
|
, potentialP2shGains: potentialP2shGains / tx.weight
|
|
};
|
|
}
|
|
|
|
// Utilities for segwitFeeGains
|
|
const witnessSize = (vin: Vin) => vin.witness.reduce((S, w) => S + (w.length / 2), 0);
|
|
const scriptSigSize = (vin: Vin) => vin.scriptsig ? vin.scriptsig.length / 2 : 0;
|