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85 lines
2.7 KiB
Java
85 lines
2.7 KiB
Java
/* -*- 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>, 19 Sep 1997.
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*/
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package grendel.storage;
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import calypso.util.ByteBuf;
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import java.util.Hashtable;
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/** This is a mechanism for uniqueifying MessageID objects.
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To save memory, we want all `equal' IDs to also be `=='.
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This table is how we accomplish that. See intern().
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@see MessageID
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@see ByteStringTable
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*/
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class MessageIDTable extends Obarray {
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/** This is the way we check to see if an object is in the table, or rather,
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if an object constructed from that sequence of bytes would be in the
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table. This is a kludge to get around the lack of function pointers...
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*/
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protected MessageID dummy;
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MessageIDTable(int default_size) {
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super(default_size);
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dummy = new MessageID();
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}
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MessageIDTable() {
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this(100);
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}
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/** Check whether there is a MessageID representing the given subsequence
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of bytes in the table already. Returns null, or an object from the
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table (an Integer object.)
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*/
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synchronized protected Object checkHash(byte bytes[],
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int start, int length) {
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dummy.hash = dummy.hashBytes(bytes, start, length);
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return hashtable.get(dummy);
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}
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/** Creates a new MessageID object (which will then be interned.) */
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protected Object newInternable(byte bytes[], int start, int length) {
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return new MessageID(bytes, start, length);
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}
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/** Ensures that an equivalent MessageID is present in the table, adding
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it if necessary. Returns the index in the table of that object.
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The given MessageID object <I>may</I> be stored in the table,
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without being copied.
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*/
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public int intern(MessageID id) {
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Object hashed = hashtable.get(id);
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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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hashtable.put(id, new Integer(count));
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array[count] = id;
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count++;
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return count-1;
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}
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}
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}
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