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128 lines
2.7 KiB
128 lines
2.7 KiB
/*
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* Copyright (c) 2001, 2008, Oracle and/or its affiliates. All rights reserved.
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* ORACLE PROPRIETARY/CONFIDENTIAL. Use is subject to license terms.
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*
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*
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*
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*
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*
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*
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*
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*
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*
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*
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*
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*
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*
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*
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*
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*
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*
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*
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*
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*
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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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