@vbyte/btc-dev/dist/lib/tx/decode.js

Batteries-included toolset for plebian bitcoin development

import { Stream } from '@vbyte/buff';
import { Assert } from '@vbyte/micro-lib/assert';
import { parse_error } from '@vbyte/micro-lib/util';
import { COINBASE } from '../../const.js';
export function decode_tx(txdata, use_segwit = true) {
    Assert.is_bytes(txdata, 'txdata must be hex or bytes');
    const stream = new Stream(txdata);
    const version = read_version(stream);
    const has_witness = (use_segwit)
        ? check_witness_flag(stream)
        : false;
    const vin = read_inputs(stream);
    const vout = read_outputs(stream);
    if (has_witness) {
        for (const txin of vin) {
            txin.witness = read_witness(stream);
        }
    }
    const locktime = read_locktime(stream);
    return { version, vin, vout, locktime };
}
function read_version(stream) {
    return stream.read(4).reverse().to_num();
}
function check_witness_flag(stream) {
    const [marker, flag] = [...stream.peek(2)];
    if (marker === 0) {
        stream.read(2);
        if (flag === 1) {
            return true;
        }
        else {
            throw new Error(`Invalid witness flag: ${flag}`);
        }
    }
    return false;
}
function read_inputs(stream) {
    const inputs = [];
    const vinCount = stream.varint();
    for (let i = 0; i < vinCount; i++) {
        const txinput = read_vin(stream);
        inputs.push(txinput);
    }
    return inputs;
}
function read_vin(stream) {
    const txid = stream.read(32).reverse().hex;
    const vout = stream.read(4).reverse().num;
    const script_sig = read_payload(stream);
    const sequence = stream.read(4).reverse().num;
    const witness = [];
    if (txid === COINBASE.TXID && vout === COINBASE.VOUT) {
        return { coinbase: script_sig, prevout: null, script_sig: null, sequence, txid, vout, witness };
    }
    else {
        return { coinbase: null, prevout: null, script_sig, sequence, txid, vout, witness };
    }
}
function read_outputs(stream) {
    const outputs = [];
    const vcount = stream.varint();
    for (let i = 0; i < vcount; i++) {
        try {
            outputs.push(read_vout(stream));
        }
        catch (error) {
            throw new Error(`failed to decode output: ${i}: ${parse_error(error)}`);
        }
    }
    return outputs;
}
function read_vout(stream) {
    const value = stream.read(8).reverse().big;
    const script_pk = read_payload(stream);
    Assert.exists(script_pk, 'failed to decode script_pk');
    return { value, script_pk };
}
function read_witness(stream) {
    const stack = [];
    const count = stream.varint();
    for (let i = 0; i < count; i++) {
        const element = read_payload(stream);
        if (element === null) {
            throw new Error('failed to decode witness element: ' + i);
        }
        stack.push(element);
    }
    return stack;
}
export function read_payload(stream) {
    const size = stream.varint('le');
    return (size > 0) ? stream.read(size).hex : null;
}
function read_locktime(stream) {
    return stream.read(4).reverse().to_num();
}