| /* BasePRNG.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.prng; |
| |
| import java.util.Map; |
| |
| /** |
| * An abstract class to facilitate implementing PRNG algorithms. |
| */ |
| public abstract class BasePRNG |
| implements IRandom |
| { |
| /** The canonical name prefix of the PRNG algorithm. */ |
| protected String name; |
| |
| /** Indicate if this instance has already been initialised or not. */ |
| protected boolean initialised; |
| |
| /** A temporary buffer to serve random bytes. */ |
| protected byte[] buffer; |
| |
| /** The index into buffer of where the next byte will come from. */ |
| protected int ndx; |
| |
| /** |
| * Trivial constructor for use by concrete subclasses. |
| * |
| * @param name the canonical name of this instance. |
| */ |
| protected BasePRNG(String name) |
| { |
| super(); |
| |
| this.name = name; |
| initialised = false; |
| buffer = new byte[0]; |
| } |
| |
| public String name() |
| { |
| return name; |
| } |
| |
| public void init(Map attributes) |
| { |
| this.setup(attributes); |
| |
| ndx = 0; |
| initialised = true; |
| } |
| |
| public byte nextByte() throws IllegalStateException, LimitReachedException |
| { |
| if (! initialised) |
| throw new IllegalStateException(); |
| |
| return nextByteInternal(); |
| } |
| |
| public void nextBytes(byte[] out) throws IllegalStateException, |
| LimitReachedException |
| { |
| nextBytes(out, 0, out.length); |
| } |
| |
| public void nextBytes(byte[] out, int offset, int length) |
| throws IllegalStateException, LimitReachedException |
| { |
| if (! initialised) |
| throw new IllegalStateException("not initialized"); |
| |
| if (length == 0) |
| return; |
| |
| if (offset < 0 || length < 0 || offset + length > out.length) |
| throw new ArrayIndexOutOfBoundsException("offset=" + offset + " length=" |
| + length + " limit=" |
| + out.length); |
| if (ndx >= buffer.length) |
| { |
| fillBlock(); |
| ndx = 0; |
| } |
| int count = 0; |
| while (count < length) |
| { |
| int amount = Math.min(buffer.length - ndx, length - count); |
| System.arraycopy(buffer, ndx, out, offset + count, amount); |
| count += amount; |
| ndx += amount; |
| if (ndx >= buffer.length) |
| { |
| fillBlock(); |
| ndx = 0; |
| } |
| } |
| } |
| |
| public void addRandomByte(byte b) |
| { |
| throw new UnsupportedOperationException("random state is non-modifiable"); |
| } |
| |
| public void addRandomBytes(byte[] buffer) |
| { |
| addRandomBytes(buffer, 0, buffer.length); |
| } |
| |
| public void addRandomBytes(byte[] buffer, int offset, int length) |
| { |
| throw new UnsupportedOperationException("random state is non-modifiable"); |
| } |
| |
| public boolean isInitialised() |
| { |
| return initialised; |
| } |
| |
| private byte nextByteInternal() throws LimitReachedException |
| { |
| if (ndx >= buffer.length) |
| { |
| this.fillBlock(); |
| ndx = 0; |
| } |
| |
| return buffer[ndx++]; |
| } |
| |
| public Object clone() throws CloneNotSupportedException |
| { |
| BasePRNG result = (BasePRNG) super.clone(); |
| if (this.buffer != null) |
| result.buffer = (byte[]) this.buffer.clone(); |
| |
| return result; |
| } |
| |
| public abstract void setup(Map attributes); |
| |
| public abstract void fillBlock() throws LimitReachedException; |
| } |