code: function padValue(value, length) {
    assert.strictEqual(typeof value, 'string');
    assert.strictEqual(typeof length, 'number');
  
    var result = value;
  
    while (result.length < length) {
      result = '0' + result;
    }
  
    return result;
  }
docs: Pad the value of a fixed-length field
  
  @param {String} value
  @param {Number} length
  @return {String}