BIF Parser

bif.js

function Buffer(a) {
  this.buffer = a;
  this.position = 0;
}
Buffer.prototype = {
  seek: function(a) {
    this.position = a;
  },
  skip: function(a) {
    this.position += a;
  },
  remaining: function() {
    return this.buffer.length - this.position;
  },
  next: function() {
    return this.buffer[this.position++];
  },
  readLength: function(a) {
    var b = this.position;
    this.position += a;
    a = this.buffer;
    return a.subarray
      ? a.subarray(b, this.position)
      : a.slice(b, this.position);
  },
  hc: function(a) {
    for (var b = 0; a--; ) b = 256 * b + this.buffer[this.position++];
    return b;
  },
  bo: function(a) {
    for (var b = ""; a--; )
      b += String.fromCharCode(this.buffer[this.position++]);
    return b;
  },
  EDa: function() {
    for (var a = "", b; (b = this.next()); ) a += String.fromCharCode(b);
    return a;
  },
  Vb: function() {
    return this.hc(2);
  },
  sa: function() {
    return this.hc(4);
  },
  Ld: function() {
    return this.hc(8);
  },
  Y6: function() {
    return this.hc(2) / 256;
  },
  HR: function() {
    return this.hc(4) / 65536;
  },
  kz: function(a) {
    for (var b, c = ""; a--; )
      (b = this.next()),
        (c += "0123456789ABCDEF"[b >>> 4] + "0123456789ABCDEF"[b & 15]);
    return c;
  },
  au: function() {
    return (
      this.kz(4) +
      "-" +
      this.kz(2) +
      "-" +
      this.kz(2) +
      "-" +
      this.kz(2) +
      "-" +
      this.kz(6)
    );
  },
  readBytes: function(a) {
    for (var b = 0, c = 0; c < a; c++) b += this.next() << (c << 3);
    return b;
  },
  readFour: function() {
    return this.readBytes(4);
  },
  WT: function(a) {
    this.buffer[this.position++] = a;
  },
  Y9: function(a, b) {
    this.position += b;
    for (var c = 1; c <= b; c++)
      (this.buffer[this.position - c] = a & 255), (a = Math.floor(a / 256));
  },
  pJa: function(a) {
    for (var b = a.length, c = 0; c < b; c++)
      this.buffer[this.position++] = a[c];
  },
  cA: function(a, b) {
    this.pJa(a.readLength(b));
  }
};

var BIF_VERSION = 0;
var BIF_MAGIC = [137, 66, 73, 70, 13, 10, 26, 10];
var BIF_META_LENGTH = 44;
function parse(a) {
  if (!a) throw new Error("invalid array buffer");
  var b = new Uint8Array(a);
  a = new Buffer(b);
  var info = (function(a) {
    if (a.remaining() < BIF_MAGIC.length + 4 + 4 + 4 + BIF_META_LENGTH)
      throw new Error("array buffer too short");
    BIF_MAGIC.forEach(function(b) {
      if (b != a.next()) throw new Error("BIF has invalid magic.");
    });
    var version = a.readFour();
    if (version > BIF_VERSION) throw new Error("BIF version in unsupported");
    var frames = a.readFour();
    if (frames == 0) throw new Error("BIF has no frames.");
    var f = a.readFour(),
      meta = a.readLength(BIF_META_LENGTH);
    return { version: version, frames: frames, k9: f, meta: meta };
  })(a);
  a = (function(a) {
    for (var f = [], g = 0; g <= info.frames; g++) {
      var k,
        h = { timestamp: a.readFour(), offset: a.readFour() };
      void 0 != k && f.push(b.subarray(k.offset, h.offset));
      k = h;
    }
    return f;
  })(a);
  return { info: info, images: a };
}

const fs = require("fs");
// wget https://occ-0-1683-300.1.nflxso.net/tp/tpa3/888/c3813c1cd2386ddb5efbc41a67029348.bif -O test.bif
const bif = fs.readFileSync("./test.bif");
const thumbs = parse(bif);
thumbs.images.forEach((image, i) => {
  const thumbPath = `thumb/${i}.jpg`;
  fs.writeFileSync(thumbPath, image);
});