| /* BaseHash.java -- |
| Copyright (C) 2001, 2002, 2006 Free Software Foundation, Inc. |
| |
| This file is a part of GNU Classpath. |
| |
| GNU Classpath is free software; you can redistribute it and/or modify |
| it under the terms of the GNU General Public License as published by |
| the Free Software Foundation; either version 2 of the License, or (at |
| your option) any later version. |
| |
| GNU Classpath 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 for more details. |
| |
| You should have received a copy of the GNU General Public License |
| along with GNU Classpath; if not, write to the Free Software |
| Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 |
| USA |
| |
| Linking this library statically or dynamically with other modules is |
| making a combined work based on this library. Thus, the terms and |
| conditions of the GNU General Public License cover the whole |
| combination. |
| |
| As a special exception, the copyright holders of this library give you |
| permission to link this library with independent modules to produce an |
| executable, regardless of the license terms of these independent |
| modules, and to copy and distribute the resulting executable under |
| terms of your choice, provided that you also meet, for each linked |
| independent module, the terms and conditions of the license of that |
| module. An independent module is a module which is not derived from |
| or based on this library. If you modify this library, you may extend |
| this exception to your version of the library, but you are not |
| obligated to do so. If you do not wish to do so, delete this |
| exception statement from your version. */ |
| |
| |
| package gnu.java.security.hash; |
| |
| /** |
| * A base abstract class to facilitate hash implementations. |
| */ |
| public abstract class BaseHash |
| implements IMessageDigest |
| { |
| /** The canonical name prefix of the hash. */ |
| protected String name; |
| |
| /** The hash (output) size in bytes. */ |
| protected int hashSize; |
| |
| /** The hash (inner) block size in bytes. */ |
| protected int blockSize; |
| |
| /** Number of bytes processed so far. */ |
| protected long count; |
| |
| /** Temporary input buffer. */ |
| protected byte[] buffer; |
| |
| /** |
| * Trivial constructor for use by concrete subclasses. |
| * |
| * @param name the canonical name prefix of this instance. |
| * @param hashSize the block size of the output in bytes. |
| * @param blockSize the block size of the internal transform. |
| */ |
| protected BaseHash(String name, int hashSize, int blockSize) |
| { |
| super(); |
| |
| this.name = name; |
| this.hashSize = hashSize; |
| this.blockSize = blockSize; |
| this.buffer = new byte[blockSize]; |
| |
| resetContext(); |
| } |
| |
| public String name() |
| { |
| return name; |
| } |
| |
| public int hashSize() |
| { |
| return hashSize; |
| } |
| |
| public int blockSize() |
| { |
| return blockSize; |
| } |
| |
| public void update(byte b) |
| { |
| // compute number of bytes still unhashed; ie. present in buffer |
| int i = (int) (count % blockSize); |
| count++; |
| buffer[i] = b; |
| if (i == (blockSize - 1)) |
| transform(buffer, 0); |
| } |
| |
| public void update(byte[] b) |
| { |
| update(b, 0, b.length); |
| } |
| |
| public void update(byte[] b, int offset, int len) |
| { |
| int n = (int) (count % blockSize); |
| count += len; |
| int partLen = blockSize - n; |
| int i = 0; |
| |
| if (len >= partLen) |
| { |
| System.arraycopy(b, offset, buffer, n, partLen); |
| transform(buffer, 0); |
| for (i = partLen; i + blockSize - 1 < len; i += blockSize) |
| transform(b, offset + i); |
| |
| n = 0; |
| } |
| |
| if (i < len) |
| System.arraycopy(b, offset + i, buffer, n, len - i); |
| } |
| |
| public byte[] digest() |
| { |
| byte[] tail = padBuffer(); // pad remaining bytes in buffer |
| update(tail, 0, tail.length); // last transform of a message |
| byte[] result = getResult(); // make a result out of context |
| |
| reset(); // reset this instance for future re-use |
| |
| return result; |
| } |
| |
| public void reset() |
| { // reset this instance for future re-use |
| count = 0L; |
| for (int i = 0; i < blockSize;) |
| buffer[i++] = 0; |
| |
| resetContext(); |
| } |
| |
| public abstract Object clone(); |
| |
| public abstract boolean selfTest(); |
| |
| /** |
| * Returns the byte array to use as padding before completing a hash |
| * operation. |
| * |
| * @return the bytes to pad the remaining bytes in the buffer before |
| * completing a hash operation. |
| */ |
| protected abstract byte[] padBuffer(); |
| |
| /** |
| * Constructs the result from the contents of the current context. |
| * |
| * @return the output of the completed hash operation. |
| */ |
| protected abstract byte[] getResult(); |
| |
| /** Resets the instance for future re-use. */ |
| protected abstract void resetContext(); |
| |
| /** |
| * The block digest transformation per se. |
| * |
| * @param in the <i>blockSize</i> long block, as an array of bytes to digest. |
| * @param offset the index where the data to digest is located within the |
| * input buffer. |
| */ |
| protected abstract void transform(byte[] in, int offset); |
| } |