fastForwardTo(c) {
    while (++this.index < this.buffer.length) {
      const cc = this.buffer.charCodeAt(this.index);
      if (cc === 10) {
        this.newlines.push(this.index);
      }
      if (cc === c) {
        return true;
      }
    }
    this.index = this.buffer.length - 1;
    return false;
  }
When we wait for one specific character, we can speed things up
by skipping through the buffer until we find it.

@returns Whether the character was found.