code: private byte[] getBuffer(byte b) {
  		if (b != 0 & b != -1) return null;
  		byte[] buffer;
  		switch (b) {
  		case 0: buffer = sZerosBuffer; break;
  		case -1 : buffer = sOnesBuffer; break;
  		default: return null;
  		}
  
  		if (buffer == null) {
  			buffer = new byte[PAD_BUFFER];
  			if (b != 0) {
  				Arrays.fill(buffer, b);
  				sOnesBuffer = buffer;
  			} else {
  				sZerosBuffer = buffer;
  			}
  		}
  		return buffer;
  	}
docs: private utility methods