128 lines
3.7 KiB
Java
128 lines
3.7 KiB
Java
/*
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* Copyright (c) 2001, 2008, Oracle and/or its affiliates. All rights reserved.
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* DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
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*
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* This code is free software; you can redistribute it and/or modify it
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* under the terms of the GNU General Public License version 2 only, as
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* published by the Free Software Foundation. Oracle designates this
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* particular file as subject to the "Classpath" exception as provided
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* by Oracle in the LICENSE file that accompanied this code.
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*
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* This code is distributed in the hope that it will be useful, but WITHOUT
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* ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
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* FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
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* version 2 for more details (a copy is included in the LICENSE file that
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* accompanied this code).
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*
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* You should have received a copy of the GNU General Public License version
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* 2 along with this work; if not, write to the Free Software Foundation,
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* Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
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*
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* Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
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* or visit www.oracle.com if you need additional information or have any
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* questions.
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*/
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package javax.swing.text;
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import java.util.ArrayList;
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import java.util.List;
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/**
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* SegmentCache caches <code>Segment</code>s to avoid continually creating
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* and destroying of <code>Segment</code>s. A common use of this class would
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* be:
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* <pre>
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* Segment segment = segmentCache.getSegment();
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* // do something with segment
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* ...
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* segmentCache.releaseSegment(segment);
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* </pre>
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*
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*/
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class SegmentCache {
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/**
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* A global cache.
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*/
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private static SegmentCache sharedCache = new SegmentCache();
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/**
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* A list of the currently unused Segments.
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*/
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private List<Segment> segments;
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/**
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* Returns the shared SegmentCache.
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*/
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public static SegmentCache getSharedInstance() {
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return sharedCache;
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}
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/**
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* A convenience method to get a Segment from the shared
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* <code>SegmentCache</code>.
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*/
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public static Segment getSharedSegment() {
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return getSharedInstance().getSegment();
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}
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/**
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* A convenience method to release a Segment to the shared
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* <code>SegmentCache</code>.
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*/
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public static void releaseSharedSegment(Segment segment) {
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getSharedInstance().releaseSegment(segment);
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}
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/**
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* Creates and returns a SegmentCache.
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*/
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public SegmentCache() {
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segments = new ArrayList<Segment>(11);
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}
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/**
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* Returns a <code>Segment</code>. When done, the <code>Segment</code>
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* should be recycled by invoking <code>releaseSegment</code>.
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*/
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public Segment getSegment() {
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synchronized(this) {
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int size = segments.size();
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if (size > 0) {
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return segments.remove(size - 1);
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}
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}
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return new CachedSegment();
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}
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/**
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* Releases a Segment. You should not use a Segment after you release it,
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* and you should NEVER release the same Segment more than once, eg:
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* <pre>
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* segmentCache.releaseSegment(segment);
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* segmentCache.releaseSegment(segment);
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* </pre>
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* Will likely result in very bad things happening!
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*/
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public void releaseSegment(Segment segment) {
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if (segment instanceof CachedSegment) {
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synchronized(this) {
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segment.array = null;
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segment.count = 0;
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segments.add(segment);
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}
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}
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}
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/**
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* CachedSegment is used as a tagging interface to determine if
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* a Segment can successfully be shared.
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*/
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private static class CachedSegment extends Segment {
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}
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}
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