private byte[] resetAndRepeatDigest(byte[] digestData) {
		final int digestCount = Math.max(1, this.digestCount);
		reset();
		for (int i = 0; i < digestCount - 1; i++) {
			digestData = doDigest(digestData);
			reset();
		}
		return digestData;
	}
private byte [ ] resetAndRepeatDigest ( byte [ ] digestData ) { final int digestCount = Math . max ( 1 , this . digestCount ) ; reset ( ) ; for ( int i = 0 ; i < digestCount - 1 ; i ++ ) { digestData = doDigest ( digestData ) ; reset ( ) ; } return digestData ; }
重复计算摘要，取决于{@link #digestCount} 值<br>
每次计算摘要前都会重置{@link #digest}

@param digestData 第一次摘要过的数据
@return 摘要