@Override
  public int read(byte[] b, int off, int len) throws IOException {
    int ret = stream.read(b, off, len);
    crc.update(b, off, ret);
    return ret;
  }
Create a CrcInputStream using the specified CRC generator
@param in
ambry-utils/src/main/java/com/github/ambry/utils/CrcInputStream.java