src/java.base/share/classes/com/sun/crypto/provider/Padding.java

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package com.sun.crypto.provider;

import javax.crypto.ShortBufferException;

/**
 * Padding interface.
 *
 * This interface is implemented by general-purpose padding schemes, such as
 * the one described in PKCS#5.
 *
 * @author Jan Luehe
 * @author Gigi Ankeny
 *
 *
 * @see PKCS5Padding
 */

interface Padding {

    /**
     * Adds the given number of padding bytes to the data input.
     * The value of the padding bytes is determined
     * by the specific padding mechanism that implements this
     * interface.
     *
     * @param in the input buffer with the data to pad
     * @param off the offset in <code>in</code> where the padding bytes
     *  are appended
     * @param len the number of padding bytes to add
     *
     * @exception ShortBufferException if <code>in</code> is too small to hold
     * the padding bytes
     */
    void padWithLen(byte[] in, int off, int len) throws ShortBufferException;

    /**
     * Returns the index where padding starts.
     *
     * <p>Given a buffer with data and their padding, this method returns the
     * index where the padding starts.
     *
     * @param in the buffer with the data and their padding
     * @param off the offset in <code>in</code> where the data starts
     * @param len the length of the data and their padding
     *
     * @return the index where the padding starts, or -1 if the input is
     * not properly padded
     */
    int unpad(byte[] in, int off, int len);

    /**
     * Determines how long the padding will be for a given input length.
     *
     * @param len the length of the data to pad
     *
     * @return the length of the padding
     */
    int padLength(int len);
}