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