@ledgerhq/hw-app-btc/lib-es/splitTransaction.js

Ledger Hardware Wallet Bitcoin Application API

import { log } from "@ledgerhq/logs";
import { getVarint } from "./varint";
import { formatTransactionDebug } from "./debug";
export function splitTransaction(transactionHex, isSegwitSupported = false, hasExtraData = false, additionals = []) {
    const inputs = [];
    const outputs = [];
    let witness = false;
    let offset = 0;
    const timestamp = Buffer.alloc(0);
    let nExpiryHeight = Buffer.alloc(0);
    let nVersionGroupId = Buffer.alloc(0);
    let extraData = Buffer.alloc(0);
    let witnessScript, locktime;
    const isDecred = additionals.includes("decred");
    const isZencash = additionals.includes("zencash");
    const isZcash = additionals.includes("zcash");
    const transaction = Buffer.from(transactionHex, "hex");
    const version = transaction.slice(offset, offset + 4);
    const overwinter = version.equals(Buffer.from([0x03, 0x00, 0x00, 0x80])) ||
        version.equals(Buffer.from([0x04, 0x00, 0x00, 0x80])) ||
        version.equals(Buffer.from([0x05, 0x00, 0x00, 0x80]));
    const isZcashv5 = isZcash && version.equals(Buffer.from([0x05, 0x00, 0x00, 0x80]));
    offset += 4;
    if (isSegwitSupported &&
        transaction[offset] === 0 &&
        transaction[offset + 1] !== 0 &&
        !isZencash) {
        offset += 2;
        witness = true;
    }
    if (overwinter) {
        nVersionGroupId = transaction.slice(offset, 4 + offset);
        offset += 4;
    }
    if (isZcashv5) {
        locktime = transaction.slice(offset + 4, offset + 8);
        nExpiryHeight = transaction.slice(offset + 8, offset + 12);
        offset += 12;
    }
    let varint = getVarint(transaction, offset);
    const numberInputs = varint[0];
    offset += varint[1];
    for (let i = 0; i < numberInputs; i++) {
        const prevout = transaction.slice(offset, offset + 36);
        offset += 36;
        let script = Buffer.alloc(0);
        let tree = Buffer.alloc(0);
        //No script for decred, it has a witness
        if (!isDecred) {
            varint = getVarint(transaction, offset);
            offset += varint[1];
            script = transaction.slice(offset, offset + varint[0]);
            offset += varint[0];
        }
        else {
            //Tree field
            tree = transaction.slice(offset, offset + 1);
            offset += 1;
        }
        const sequence = transaction.slice(offset, offset + 4);
        offset += 4;
        inputs.push({
            prevout,
            script,
            sequence,
            tree,
        });
    }
    varint = getVarint(transaction, offset);
    const numberOutputs = varint[0];
    offset += varint[1];
    for (let i = 0; i < numberOutputs; i++) {
        const amount = transaction.slice(offset, offset + 8);
        offset += 8;
        if (isDecred) {
            //Script version
            offset += 2;
        }
        varint = getVarint(transaction, offset);
        offset += varint[1];
        const script = transaction.slice(offset, offset + varint[0]);
        offset += varint[0];
        outputs.push({
            amount,
            script,
        });
    }
    if (witness) {
        witnessScript = transaction.slice(offset, -4);
        locktime = transaction.slice(transaction.length - 4);
    }
    else if (!isZcashv5) {
        locktime = transaction.slice(offset, offset + 4);
    }
    offset += 4;
    if ((overwinter || isDecred) && !isZcashv5) {
        nExpiryHeight = transaction.slice(offset, offset + 4);
        offset += 4;
    }
    if (hasExtraData) {
        extraData = transaction.slice(offset);
    }
    //Get witnesses for Decred
    if (isDecred) {
        varint = getVarint(transaction, offset);
        offset += varint[1];
        if (varint[0] !== numberInputs) {
            throw new Error("splitTransaction: incoherent number of witnesses");
        }
        for (let i = 0; i < numberInputs; i++) {
            //amount
            offset += 8;
            //block height
            offset += 4;
            //block index
            offset += 4;
            //Script size
            varint = getVarint(transaction, offset);
            offset += varint[1];
            const script = transaction.slice(offset, offset + varint[0]);
            offset += varint[0];
            inputs[i].script = script;
        }
    }
    const t = {
        version,
        inputs,
        outputs,
        locktime,
        witness: witnessScript,
        timestamp,
        nVersionGroupId,
        nExpiryHeight,
        extraData,
    };
    log("btc", `splitTransaction ${transactionHex}:\n${formatTransactionDebug(t)}`);
    return t;
}
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