docs: protected int expand(int len) {
          int newcount = count + len;
          if (newcount <= content.length) return 0;
          byte[] newdata = new byte[Math.max(content.length * 3 / 2, newcount)];
          System.arraycopy(content, 0, newdata, 0, count);
          this.content = newdata;
          return 0;
      }