208 lines
7.2 KiB
Java
208 lines
7.2 KiB
Java
/*
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* Copyright (c) 1997, 2013, Oracle and/or its affiliates. All rights reserved.
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* DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
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*
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* This code is free software; you can redistribute it and/or modify it
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* under the terms of the GNU General Public License version 2 only, as
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* published by the Free Software Foundation. Oracle designates this
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* particular file as subject to the "Classpath" exception as provided
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* by Oracle in the LICENSE file that accompanied this code.
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*
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* This code is distributed in the hope that it will be useful, but WITHOUT
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* ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
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* FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
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* version 2 for more details (a copy is included in the LICENSE file that
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* accompanied this code).
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*
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* You should have received a copy of the GNU General Public License version
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* 2 along with this work; if not, write to the Free Software Foundation,
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* Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
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*
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* Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
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* or visit www.oracle.com if you need additional information or have any
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* questions.
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*/
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package java.security;
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import java.nio.ByteBuffer;
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import sun.security.jca.JCAUtil;
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/**
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* This class defines the <i>Service Provider Interface</i> (<b>SPI</b>)
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* for the {@code MessageDigest} class, which provides the functionality
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* of a message digest algorithm, such as MD5 or SHA. Message digests are
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* secure one-way hash functions that take arbitrary-sized data and output a
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* fixed-length hash value.
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*
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* <p> All the abstract methods in this class must be implemented by a
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* cryptographic service provider who wishes to supply the implementation
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* of a particular message digest algorithm.
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*
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* <p> Implementations are free to implement the Cloneable interface.
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*
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* @author Benjamin Renaud
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* @since 1.2
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*
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*
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* @see MessageDigest
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*/
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public abstract class MessageDigestSpi {
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// for re-use in engineUpdate(ByteBuffer input)
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private byte[] tempArray;
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/**
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* Returns the digest length in bytes.
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*
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* <p>This concrete method has been added to this previously-defined
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* abstract class. (For backwards compatibility, it cannot be abstract.)
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*
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* <p>The default behavior is to return 0.
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*
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* <p>This method may be overridden by a provider to return the digest
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* length.
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*
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* @return the digest length in bytes.
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*
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* @since 1.2
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*/
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protected int engineGetDigestLength() {
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return 0;
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}
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/**
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* Updates the digest using the specified byte.
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*
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* @param input the byte to use for the update.
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*/
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protected abstract void engineUpdate(byte input);
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/**
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* Updates the digest using the specified array of bytes,
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* starting at the specified offset.
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*
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* @param input the array of bytes to use for the update.
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*
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* @param offset the offset to start from in the array of bytes.
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*
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* @param len the number of bytes to use, starting at
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* {@code offset}.
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*/
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protected abstract void engineUpdate(byte[] input, int offset, int len);
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/**
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* Update the digest using the specified ByteBuffer. The digest is
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* updated using the {@code input.remaining()} bytes starting
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* at {@code input.position()}.
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* Upon return, the buffer's position will be equal to its limit;
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* its limit will not have changed.
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*
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* @param input the ByteBuffer
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* @since 1.5
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*/
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protected void engineUpdate(ByteBuffer input) {
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if (input.hasRemaining() == false) {
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return;
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}
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if (input.hasArray()) {
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byte[] b = input.array();
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int ofs = input.arrayOffset();
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int pos = input.position();
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int lim = input.limit();
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engineUpdate(b, ofs + pos, lim - pos);
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input.position(lim);
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} else {
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int len = input.remaining();
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int n = JCAUtil.getTempArraySize(len);
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if ((tempArray == null) || (n > tempArray.length)) {
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tempArray = new byte[n];
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}
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while (len > 0) {
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int chunk = Math.min(len, tempArray.length);
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input.get(tempArray, 0, chunk);
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engineUpdate(tempArray, 0, chunk);
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len -= chunk;
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}
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}
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}
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/**
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* Completes the hash computation by performing final
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* operations such as padding. Once {@code engineDigest} has
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* been called, the engine should be reset (see
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* {@link #engineReset() engineReset}).
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* Resetting is the responsibility of the
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* engine implementor.
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*
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* @return the array of bytes for the resulting hash value.
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*/
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protected abstract byte[] engineDigest();
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/**
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* Completes the hash computation by performing final
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* operations such as padding. Once {@code engineDigest} has
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* been called, the engine should be reset (see
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* {@link #engineReset() engineReset}).
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* Resetting is the responsibility of the
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* engine implementor.
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*
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* This method should be abstract, but we leave it concrete for
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* binary compatibility. Knowledgeable providers should override this
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* method.
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*
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* @param buf the output buffer in which to store the digest
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*
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* @param offset offset to start from in the output buffer
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*
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* @param len number of bytes within buf allotted for the digest.
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* Both this default implementation and the SUN provider do not
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* return partial digests. The presence of this parameter is solely
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* for consistency in our API's. If the value of this parameter is less
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* than the actual digest length, the method will throw a DigestException.
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* This parameter is ignored if its value is greater than or equal to
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* the actual digest length.
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*
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* @return the length of the digest stored in the output buffer.
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*
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* @exception DigestException if an error occurs.
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*
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* @since 1.2
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*/
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protected int engineDigest(byte[] buf, int offset, int len)
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throws DigestException {
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byte[] digest = engineDigest();
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if (len < digest.length)
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throw new DigestException("partial digests not returned");
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if (buf.length - offset < digest.length)
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throw new DigestException("insufficient space in the output "
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+ "buffer to store the digest");
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System.arraycopy(digest, 0, buf, offset, digest.length);
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return digest.length;
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}
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/**
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* Resets the digest for further use.
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*/
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protected abstract void engineReset();
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/**
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* Returns a clone if the implementation is cloneable.
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*
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* @return a clone if the implementation is cloneable.
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*
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* @exception CloneNotSupportedException if this is called on an
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* implementation that does not support {@code Cloneable}.
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*/
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public Object clone() throws CloneNotSupportedException {
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if (this instanceof Cloneable) {
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return super.clone();
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} else {
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throw new CloneNotSupportedException();
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}
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}
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}
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