/*
* Copyright (c) 1997, 2013, Oracle and/or its affiliates. All rights reserved.
* ORACLE PROPRIETARY/CONFIDENTIAL. Use is subject to license terms.
*
*
*
*
*
*
*
*
*
*
*
*
*
*
*
*
*
*
*
*
*/
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} 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}.
*/
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()} bytes starting
* at {@code input.position()}.
* 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} 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} 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}.
*/
public
Object clone() throws
CloneNotSupportedException {
if (this instanceof
Cloneable) {
return super.clone();
} else {
throw new
CloneNotSupportedException();
}
}
}