binary-vdf-parser

Binary VDF Parser

binary-vdf-parser is a module for parsing Valve binary VDF files such as appinfo.vdf or shortcuts.vdf. It was created for the Skizzium Launcher after encountering issues parsing appinfo.vdf with existing packages such as steam-binary-vdf and binary-vdf.

Usage

Install with npm i --save binary-vdf-parser

import fs from 'fs';
import path from 'path';
import { readVdf } from './index';

const filepath = path.resolve('path/to/file.vdf');
const buffer = fs.readFileSync(filepath);
const appinfo = readVdf(buffer);

console.log(appinfo);

Decoding Guide

VDFs are formatted in LE (little endian), meaning multi-byte values should be interpreted right-to-left. For example, a 16bit integer 0x01 0x00 should be interpreted as 1 instead of 256. In Node.js, use buffer.readUInt32LE() to read a 32bit unsigned integer.

There are a few bytes that will appear before any data. These bytes indicate which type of data will follow:

• The first data type is a map (or object, in JS terms), represented by 0x00. The next byte will be the first entry inside of this new map.
• The second data type is a string, represented by 0x01. The string is utf8-encoded, lasting until a NULL terminator is found (0x00). This is the only exception to 0x00, changing the meaning from "Create a new map" to "Reached the end of a string". No other data types end in 0x00.
• The third data type is an integer, represented by 0x02. This is an unsigned 32bit int, meaning it will always consume exactly 4 bytes.
• The last data type indicates the end of a map, represented by 0x08. The next byte will be the beginning of the next entry in the "parent" map.

My Notes

Below are the notes I took while learning the data. I opened an appinfo.vdf file with HxD (a hex editor) and went through each byte, comparing it to a premade JSON dump. I mentally converted each byte into the following symbols and added plaintext/numbers where it called for them. I then used the symbols' descriptions to convert it to JSON until I felt I got the hang of it and could write it in code.

; 0x00: Null terminator (terminate string if possible, otherwise begin map)
" 0x01: New property (string)
# 0x02: New property (int)
< 0x08: End map

appinfo;#appid;7;common;"name;Steam Client;"type;Config;;associations;<#gameid;7<;extended;"beta_name_1;Steam Beta Update;"

[
  {
    appid: 7,
    common: {
      name: 'Steam Client',
      type: 'Config',
      associations: {}
    },
    gameid: 7,
    extended: {
      beta_name_1: 'Steam Beta Update',
      beta_contentlist_1: 'steamexe publicbeta',
      beta_name_2: 'Steam Deck Stable',
      beta_contentlist_2: 'steamexe steamdeck_stable',
      beta_name_3: 'Steam Deck Beta',
      // ...
    }
  }
]