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591 lines
20 KiB
Java
591 lines
20 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
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* License Version 1.1 (the "License"); you may not use this file
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* except in compliance with the License. You may obtain a copy of
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* the License at http://www.mozilla.org/MPL/
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*
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* Software distributed under the License is distributed on an "AS
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* IS" basis, WITHOUT WARRANTY OF ANY KIND, either express or
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* implied. See the License for the specific language governing
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* rights and limitations 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
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* Copyright (C) 1997 Netscape Communications Corporation. All
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* Rights Reserved.
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*
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* Contributor(s):
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*
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* Created: Jamie Zawinski <jwz@netscape.com>, 13 Jun 1995.
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* Ported from C on 14 Aug 1997.
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*/
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package grendel.view;
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import java.util.Hashtable;
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import java.util.Enumeration;
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import calypso.util.Assert;
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/**
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This arranges a set of messages into a thread hierarchy, by references.
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The sets of messages are accessed via the IThreadable interface.
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@see IThreadable
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@see Sorter
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*/
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class Threader {
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private ThreadContainer root_node; // has kids, and no next
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private Hashtable id_table; // maps message IDs to ThreadContainers
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private int bogus_id_count = 0; // tick of how many dup IDs we've seen
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/** Threads the set of messages indicated by threadable_root.
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The IThreadable returned is the new first element of the root set.
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@param threadable_root The start of the list.
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*/
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public IThreadable thread(IThreadable threadable_root) {
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if (threadable_root == null) return null;
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id_table = new Hashtable();
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for (Enumeration e = threadable_root.allElements(); e.hasMoreElements();) {
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IThreadable t = (IThreadable) e.nextElement();
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if (!t.isDummy())
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buildContainer(t);
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}
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root_node = findRootSet();
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id_table.clear();
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id_table = null;
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pruneEmptyContainers(root_node);
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// We do this so to avoid flipping the input order each time through.
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root_node.reverseChildren();
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gatherSubjects();
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if (root_node.next != null)
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throw new Error("root node has a next?" + root_node);
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for (ThreadContainer r = root_node.child; r != null; r = r.next) {
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// If this direct child of the root node has no threadable in it,
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// manufacture a dummy container to bind its children together.
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// Note that these dummies can only ever occur as elements of
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// the root set.
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if (r.threadable == null)
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r.threadable = r.child.threadable.makeDummy();
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}
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IThreadable result = (root_node.child == null
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? null
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: root_node.child.threadable);
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// Flush the tree structure of each element of the root set down into
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// their underlying threadables.
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root_node.flush();
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root_node = null;
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return result;
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}
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// buildContainer() does three things:
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//
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// = It walks the tree of threadables, and wraps each in a
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// ThreadContainer object.
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// = It indexes each ThreadContainer object in the id_table, under
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// the message ID of the contained IThreadable.
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// = For each of the IThreadable's references, it ensures that there
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// is a ThreadContainer in the table (an empty one, if necessary.)
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//
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private void buildContainer(IThreadable threadable) {
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Object id = threadable.messageThreadID();
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Assert.Assertion(id != null);
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ThreadContainer c = (ThreadContainer) id_table.get (id);
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if (c != null) {
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// There is already a ThreadContainer in the table for this ID.
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// Under normal circumstances, there will be no IThreadable in it
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// (since it was a forward reference from a References field.)
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//
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// If there is already a threadable in it, then that means there
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// are two IThreadables with the same ID. Generate a new ID for
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// this one, sigh... This ID is only used to cause the two entries
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// in the hash table to not stomp each other.
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//
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if (c.threadable != null) {
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id = "<Bogus-id:" + (bogus_id_count++) + ">";
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c = null;
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} else {
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c.threadable = threadable;
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}
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}
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// Create a ThreadContainer for this IThreadable, and index it in
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// the hash table.
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//
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if (c == null) {
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c = new ThreadContainer();
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c.threadable = threadable;
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// c.debug_id = id;
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id_table.put (id, c);
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}
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// Create ThreadContainers for each of the references which don't
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// have them. Link each of the referenced messages together in the
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// order implied by the references field, unless they are already
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// linked.
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ThreadContainer parent_ref = null;
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{
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Object refs[] = threadable.messageThreadReferences();
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int L = (refs == null ? 0 : refs.length);
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for (int i = 0; i < L; i++) {
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Object ref_string = refs[i];
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ThreadContainer ref = (ThreadContainer) id_table.get (ref_string);
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if (ref == null) {
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ref = new ThreadContainer();
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// ref.debug_id = ref_string;
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id_table.put (ref_string, ref);
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}
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// If we have references A B C D, make D be a child of C, etc,
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// except if they have parents already.
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//
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if (parent_ref != null && // there is a parent
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ref.parent == null && // don't have a parent already
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parent_ref != ref && // not a tight loop
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!parent_ref.find_child(ref)) { // not a wide loop
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// Ok, link it into the parent's child list.
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ref.parent = parent_ref;
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ref.next = parent_ref.child;
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parent_ref.child = ref;
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}
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parent_ref = ref;
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}
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}
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// At this point `parent_ref' is set to the container of the last element
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// in the references field. Make that be the parent of this container,
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// unless doing so would introduce a circularity.
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//
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if (parent_ref != null &&
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(parent_ref == c ||
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c.find_child (parent_ref)))
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parent_ref = null;
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if (c.parent != null) {
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// If it has a parent already, that's there because we saw this message
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// in a references field, and presumed a parent based on the other
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// entries in that field. Now that we have the actual message, we can
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// be more definitive, so throw away the old parent and use this new one.
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// Find this container in the parent's child-list, and unlink it.
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//
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// Note that this could cause this message to now have no parent, if it
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// has no references field, but some message referred to it as the
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// non-first element of its references. (Which would have been some
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// kind of lie...)
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//
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ThreadContainer rest, prev;
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for (prev = null, rest = c.parent.child;
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rest != null;
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prev = rest, rest = rest.next) {
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if (rest == c)
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break;
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}
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if (rest == null)
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throw new Error("didn't find " + c + " in parent " + c.parent);
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if (prev == null)
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c.parent.child = c.next;
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else
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prev.next = c.next;
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c.next = null;
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c.parent = null;
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}
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// If we have a parent, link c into the parent's child list.
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if (parent_ref != null) {
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c.parent = parent_ref;
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c.next = parent_ref.child;
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parent_ref.child = c;
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}
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}
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// Find the root set of the ThreadContainers (and return a root node.)
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// A container is in the root set if it has no parents.
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//
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private ThreadContainer findRootSet() {
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ThreadContainer root = new ThreadContainer();
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// root.debug_id = "((root))";
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for (Enumeration e = id_table.elements(); e.hasMoreElements(); ) {
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ThreadContainer c = (ThreadContainer) e.nextElement();
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if (c.parent == null) {
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if (c.next != null)
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throw new Error("c.next is " + c.next.toString());
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c.next = root.child;
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root.child = c;
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}
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}
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return root;
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}
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// Walk through the threads and discard any empty container objects.
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// After calling this, there will only be any empty container objects
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// at depth 0, and those will all have at least two kids.
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//
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private void pruneEmptyContainers(ThreadContainer parent) {
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ThreadContainer container, prev, next;
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for (prev = null, container = parent.child, next = container.next;
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container != null;
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prev = container, container = next,
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next = (container == null ? null : container.next)) {
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if (container.threadable == null &&
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container.child == null) {
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// This is an empty container with no kids. Nuke it.
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//
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// Normally such containers won't occur, but they can show up when
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// two messages have References lines that disagree. For example,
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// assuming A and B are messages, and 1, 2, and 3 are references for
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// messages we haven't seen:
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//
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// A has refs: 1 2 3
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// B has refs: 1 3
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//
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// There is ambiguity as to whether 3 is a child of 1 or 2. So,
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// depending on the processing order, we might end up with either
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//
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// -- 1
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// |-- 2
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// |-- 3
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// |-- A
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// |-- B
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// or
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// -- 1
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// |-- 2 <--- non root childless container
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// |-- 3
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// |-- A
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// |-- B
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//
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if (prev == null)
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parent.child = container.next;
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else
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prev.next = container.next;
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// Set container to prev so that prev keeps its same value
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// the next time through the loop.
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container = prev;
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} else if (container.threadable == null && // expired, and
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container.child != null && // has kids, and
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(container.parent != null || // not at root, or
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container.child.next == null)) { // only one kid
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// Expired message with kids. Promote the kids to this level.
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// Don't do this if we would be promoting them to the root level,
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// unless there is only one kid.
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ThreadContainer tail;
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ThreadContainer kids = container.child;
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// Remove this container from the list, replacing it with `kids'.
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if (prev == null)
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parent.child = kids;
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else
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prev.next = kids;
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// make each child's parent be this level's parent.
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// make the last child's next be this container's next
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// (splicing `kids' into the list in place of `container'.)
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for (tail = kids; tail.next != null; tail = tail.next)
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tail.parent = container.parent;
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tail.parent = container.parent;
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tail.next = container.next;
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// Since we've inserted items in the chain, `next' currently points
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// to the item after them (tail.next); reset that so that we process
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// the newly promoted items the very next time around.
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next = kids;
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// Set container to prev so that prev keeps its same value
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// the next time through the loop.
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container = prev;
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} else if (container.child != null) {
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// A real message with kids.
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// Iterate over its children, and try to strip out the junk.
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pruneEmptyContainers(container);
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}
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}
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}
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// If any two members of the root set have the same subject, merge them.
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// This is so that messages which don't have References headers at all
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// still get threaded (to the extent possible, at least.)
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//
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private void gatherSubjects() {
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int count = 0;
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for (ThreadContainer c = root_node.child; c != null; c = c.next)
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count++;
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// Make the hash table large enough to not need to be rehashed.
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Hashtable subj_table = new Hashtable((int) (count * 1.2), (float) 0.9);
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count = 0;
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for (ThreadContainer c = root_node.child; c != null; c = c.next) {
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IThreadable threadable = c.threadable;
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// If there is no threadable, this is a dummy node in the root set.
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// Only root set members may be dummies, and they always have at least
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// two kids. Take the first kid as representative of the subject.
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if (threadable == null)
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threadable = c.child.threadable;
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String subj = threadable.simplifiedSubject();
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if (subj == null || subj == "")
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continue;
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ThreadContainer old = (ThreadContainer) subj_table.get(subj);
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// Add this container to the table if:
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// - There is no container in the table with this subject, or
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// - This one is a dummy container and the old one is not: the dummy
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// one is more interesting as a root, so put it in the table instead.
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// - The container in the table has a "Re:" version of this subject,
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// and this container has a non-"Re:" version of this subject.
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// The non-re version is the more interesting of the two.
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//
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if (old == null ||
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(c.threadable == null && old.threadable != null) ||
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(old.threadable != null && old.threadable.subjectIsReply() &&
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c.threadable != null && !c.threadable.subjectIsReply())) {
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subj_table.put(subj, c);
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count++;
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}
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}
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if (count == 0) // if the table is empty, we're done.
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return;
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// The subj_table is now populated with one entry for each subject which
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// occurs in the root set. Now iterate over the root set, and gather
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// together the difference.
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//
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ThreadContainer prev, c, rest;
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for (prev = null, c = root_node.child, rest = c.next;
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c != null;
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prev = c, c = rest, rest = (rest == null ? null : rest.next)) {
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IThreadable threadable = c.threadable;
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if (threadable == null) // might be a dummy -- see above
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threadable = c.child.threadable;
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String subj = threadable.simplifiedSubject();
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// Don't thread together all subjectless messages; let them dangle.
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if (subj == null || subj == "")
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continue;
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ThreadContainer old = (ThreadContainer) subj_table.get(subj);
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if (old == c) // oops, that's us
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continue;
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// Ok, so now we have found another container in the root set with
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// the same subject. There are a few possibilities:
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//
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// - If both are dummies, append one's children to the other, and remove
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// the now-empty container.
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//
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// - If one container is a dummy and the other is not, make the non-dummy
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// one be a child of the dummy, and a sibling of the other "real"
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// messages with the same subject (the dummy's children.)
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//
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// - If that container is a non-dummy, and that message's subject does
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// not begin with "Re:", but *this* message's subject does, then
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// make this be a child of the other.
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//
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// - If that container is a non-dummy, and that message's subject begins
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// with "Re:", but *this* message's subject does *not*, then make that
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// be a child of this one -- they were misordered. (This happens
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// somewhat implicitly, since if there are two messages, one with Re:
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// and one without, the one without will be in the hash table,
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// regardless of the order in which they were seen.)
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//
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// - Otherwise, make a new dummy container and make both messages be a
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// child of it. This catches the both-are-replies and neither-are-
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// replies cases, and makes them be siblings instead of asserting a
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// hierarchical relationship which might not be true.
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//
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// (People who reply to messages without using "Re:" and without using
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// a References line will break this slightly. Those people suck.)
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//
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// (It has occurred to me that taking the date or message number into
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// account would be one way of resolving some of the ambiguous cases,
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// but that's not altogether straightforward either.)
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// Remove the "second" message from the root set.
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if (prev == null)
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root_node.child = c.next;
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else
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prev.next = c.next;
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c.next = null;
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if (old.threadable == null && c.threadable == null) {
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// They're both dummies; merge them.
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ThreadContainer tail;
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for (tail = old.child;
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tail != null && tail.next != null;
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tail = tail.next)
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;
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tail.next = c.child;
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for (tail = c.child; tail != null; tail = tail.next)
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tail.parent = old;
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c.child = null;
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} else if (old.threadable == null || // old is empty, or
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(c.threadable != null &&
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c.threadable.subjectIsReply() && // c has Re, and
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!old.threadable.subjectIsReply())) { // old does not.
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// Make this message be a child of the other.
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c.parent = old;
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c.next = old.child;
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old.child = c;
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} else {
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// Make the old and new messages be children of a new dummy container.
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// We do this by creating a new container object for old->msg and
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// transforming the old container into a dummy (by merely emptying it),
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// so that the hash table still points to the one that is at depth 0
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// instead of depth 1.
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ThreadContainer newc = new ThreadContainer();
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newc.threadable = old.threadable;
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// newc.debug_id = old.debug_id;
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newc.child = old.child;
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for (ThreadContainer tail = newc.child; tail != null; tail = tail.next)
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tail.parent = newc;
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old.threadable = null;
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old.child = null;
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// old.debug_id = null;
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c.parent = old;
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newc.parent = old;
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// old is now a dummy; make it have exactly two kids, c and newc.
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old.child = c;
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c.next = newc;
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}
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// we've done a merge, so keep the same `prev' next time around.
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c = prev;
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}
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subj_table.clear();
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subj_table = null;
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}
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}
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/*
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The ThreadContainer object is used to encapsulate an IThreadable object
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(it holds some intermediate state used while threading.) This is a
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private class that doesn't escape from this module.
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*/
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class ThreadContainer {
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IThreadable threadable;
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ThreadContainer parent;
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ThreadContainer child;
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ThreadContainer next;
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// Object debug_id;
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// int id2;
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// static int id2_pool = 0;
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|
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// ThreadContainer() { id2 = ++id2_pool; }
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|
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// public String toString() { return "<cont " +
|
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// id2 + " " + debug_id +
|
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// " [" + threadable + "] >"; }
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|
|
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// public void debug_print(int depth) {
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// for (int i = 0; i < depth; i++) System.out.print(" ");
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// System.out.println(this);
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// if (child != null) child.debug_print(depth+1);
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// if (next != null) next.debug_print(depth);
|
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// }
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|
|
|
// Copy the ThreadContainer tree structure down into the underlying
|
|
// IThreadable objects (that is, make the IThreadable tree look like
|
|
// the ThreadContainer tree.)
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|
//
|
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void flush() {
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|
if (parent != null && threadable == null)
|
|
// Only the root_node is allowed to not have a threadable.
|
|
throw new Error("no threadable in " + this.toString());
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|
|
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parent = null;
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|
|
|
if (threadable != null)
|
|
threadable.setChild(child == null ? null : child.threadable);
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|
|
|
if (child != null) {
|
|
child.flush();
|
|
child = null;
|
|
}
|
|
|
|
if (threadable != null)
|
|
threadable.setNext(next == null ? null : next.threadable);
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|
|
|
if (next != null) {
|
|
next.flush();
|
|
next = null;
|
|
}
|
|
|
|
threadable = null;
|
|
}
|
|
|
|
// Returns true if child is under self's tree. This is used for
|
|
// detecting circularities in the references header.
|
|
boolean find_child(ThreadContainer target) {
|
|
if (child == null)
|
|
return false;
|
|
else if (child == target)
|
|
return true;
|
|
else
|
|
return child.find_child(target);
|
|
}
|
|
|
|
void reverseChildren() {
|
|
if (child != null) {
|
|
// nreverse the children (child through child.next.next.next...)
|
|
ThreadContainer kid, prev, rest;
|
|
for (prev = null, kid = child, rest = kid.next;
|
|
kid != null;
|
|
prev = kid, kid = rest, rest = (rest == null ? null : rest.next))
|
|
kid.next = prev;
|
|
child = prev;
|
|
|
|
// then do it for the kids
|
|
for (kid = child; kid != null; kid = kid.next)
|
|
kid.reverseChildren();
|
|
}
|
|
}
|
|
}
|