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156 lines
4.4 KiB
Java
156 lines
4.4 KiB
Java
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/* -*- Mode: java; indent-tabs-mode: nil; c-basic-offset: 2 -*-
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*
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* The contents of this file are subject to the Mozilla Public License
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* Version 1.0 (the "License"); you may not use this file except in
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* compliance with the License. You may obtain a copy of the License at
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* http://www.mozilla.org/MPL/
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*
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* Software distributed under the License is distributed on an "AS IS"
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* basis, WITHOUT WARRANTY OF ANY KIND, either express or implied. See
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* the License for the specific language governing rights and limitations
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* under the License.
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*
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* The Original Code is the Grendel mail/news client.
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*
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* The Initial Developer of the Original Code is Netscape Communications
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* Corporation. Portions created by Netscape are Copyright (C) 1997
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* Netscape Communications Corporation. All Rights Reserved.
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*
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* Created: Jamie Zawinski <jwz@netscape.com>, 20 Sep 1997.
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*/
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package grendel.storage;
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import java.util.Enumeration;
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import java.util.NoSuchElementException;
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import calypso.util.ByteBuf;
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import java.util.Hashtable;
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/** Base class for objects which enable interning (uniquification) of
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objects.
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*/
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abstract class Obarray {
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/** Holds unique (non-equal) objects.
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*/
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protected Object array[];
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/** How much of the array is in use; we don't use Vector for this because
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Vector likes to expand itself by doubling its size, and we will have
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enough entries that that would suck.
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*/
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protected int count;
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/** Hashes from object keys to index-in-the-array values. (Which are
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unfortunately `Integer' objects instead of ints, because the Java
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object model is hopelessly stupid about such things.)
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*/
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protected Hashtable hashtable;
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Obarray(int default_size) {
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hashtable = new Hashtable(default_size);
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array = new Object[default_size];
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count = 0;
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}
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Obarray() {
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this(100);
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}
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/** Check whether there is an object representing the given subsequence
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of bytes in the table already. This should end up doing hashtable.get()
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and returning null, or an object from the table (an Integer object.)
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*/
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abstract protected Object checkHash(byte bytes[], int start, int length);
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/** Creates a new object (which will then be interned.)
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*/
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abstract protected Object newInternable(byte bytes[], int start, int length);
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protected synchronized void ensureCapacity(int count) {
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// we're adding an item; grow the array if necessary.
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if (count >= array.length) {
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int new_size = ((array.length * 13) / 10) + 10; // grow by 30% + 10.
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Object new_array[] = new Object[new_size];
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System.arraycopy(array, 0, new_array, 0, array.length);
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array = new_array;
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}
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}
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/** Returns the numeric ID of an object containing the given bytes.
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This will be reused if possible; otherwise, a new one will be made
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and remembered in the table.
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<P>
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The ID-number may be turned into an interned object with getObject().
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*/
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public synchronized int intern(byte bytes[], int start, int length) {
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if (length <= 0) return -1;
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Object hashed = checkHash(bytes, start, length);
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if (hashed != null) {
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return ((Integer) hashed).intValue();
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} else {
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ensureCapacity(count+1);
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Object b = newInternable(bytes, start, length);
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hashtable.put(b, new Integer(count));
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array[count] = b;
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count++;
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return count-1;
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}
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}
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public int intern(ByteBuf buf) {
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return intern(buf.toBytes(), 0, buf.length());
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}
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public int intern(String s) {
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byte b[] = s.getBytes();
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return intern(b, 0, b.length);
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}
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/** Given a numberic ID number, converts it to the corresponding
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object in this table. This ID number should be one that
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was previously returned by the table's `intern()' method.
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*/
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public Object getObject(int id) {
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if (id == -1 || count <= id)
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return null;
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else
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return array[id];
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}
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public boolean isEmpty() {
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return (count == 0);
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}
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public int size() {
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return count;
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}
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public void clear() {
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hashtable.clear();
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while (count > 0)
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array[--count] = null;
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}
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public Enumeration elements() {
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return new ObarrayEnumeration(this);
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}
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}
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class ObarrayEnumeration implements Enumeration {
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int i = 0;
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Obarray a;
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public ObarrayEnumeration(Obarray a) { this.a = a; }
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public Object nextElement() {
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if (i < a.count) return a.array[i++];
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else throw new NoSuchElementException();
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}
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public boolean hasMoreElements() { return (a != null && i < a.count); }
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}
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