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package org.frameworkset.util;

import java.io.IOException;
import java.io.InputStream;
import java.security.MessageDigest;

public abstract class UpdateMessageDigestInputStream  extends InputStream {

	/**
	 * Update the message digest with the rest of the bytes in this stream.
	 * Using this method is more optimized since it avoids creating new
	 * byte arrays for each call.
	 * @param messageDigest The message digest to update
	 * @throws IOException when propagated from {@link #read()}
	 */
	public void updateMessageDigest(MessageDigest messageDigest) throws IOException {
		int data;
		while ((data = read()) != -1){
			messageDigest.update((byte) data);
		}
	}

	/**
	 * Update the message digest with the next len bytes in this stream.
	 * Using this method is more optimized since it avoids creating new
	 * byte arrays for each call.
	 * @param messageDigest The message digest to update
	 * @param len how many bytes to read from this stream and use to update the message digest
	 * @throws IOException when propagated from {@link #read()}
	 */
	public void updateMessageDigest(MessageDigest messageDigest, int len) throws IOException {
		int data;
		int bytesRead = 0;
		while (bytesRead < len && (data = read()) != -1){
			messageDigest.update((byte) data);
			bytesRead++;
		}
	}

}