code: func (c *Compressor) Ratio() int {
  	if c.inSize > 0 {
  		return (10000 * c.outSize) / c.inSize
  	}
  	return -1
  }
docs: // Ratio retrieves the compression ratio of the last compression
  // performed. Only makes sense after Close() has been called. The
  // returned value is an integer representing the size of the output as
  // a percentage of the input * 100. If the return value is -1 then it
  // indicates that there was no input.