code: function(size) {
          var result = 0,
              i;
          this.checkOffset(size);
          for (i = this.index + size - 1; i >= this.index; i--) {
              result = (result << 8) + this.byteAt(i);
          }
          this.index += size;
          return result;
      }
docs: Get the next number with a given byte size.
  @param {number} size the number of bytes to read.
  @return {number} the corresponding number.