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/*******************************************************************************
* Copyright (c) 2005, 2012 IBM Corporation and others.
* All rights reserved. This program and the accompanying materials
* are made available under the terms of the Eclipse Public License v1.0
* which accompanies this distribution, and is available at
* http://www.eclipse.org/legal/epl-v10.html
*
* Contributors:
* Anton Leherbauer (anton.leherbauer@windriver.com) - initial API and implementation
*******************************************************************************/
package org.eclipse.jface.text;
import org.eclipse.core.runtime.Assert;
/**
* Copy-on-write <code>ITextStore</code> wrapper.
* <p>
* This implementation uses an unmodifiable text store for the initial content. Upon first
* modification attempt, the unmodifiable store is replaced with a modifiable instance which must be
* supplied in the constructor.
* </p>
* <p>
* This class is not intended to be subclassed.
* </p>
*
* @since 3.2
* @noextend This class is not intended to be subclassed by clients.
*/
public class CopyOnWriteTextStore implements ITextStore {
/**
* An unmodifiable String based text store. It is not possible to modify the initial content.
* Trying to {@link #replace} a text range or {@link #set} new content will throw an
* <code>UnsupportedOperationException</code>.
*/
private static class StringTextStore implements ITextStore {
/** Minimum text limit whether to enable String copying */
private static final int SMALL_TEXT_LIMIT= 1024 * 1024;
/** Represents the content of this text store. */
private final String fText;
/** Minimum length limit below which {@link #get(int, int)} will return a String copy */
private final int fCopyLimit;
/**
* Create an empty text store.
*/
private StringTextStore() {
this(""); //$NON-NLS-1$
}
/**
* Create a text store with initial content.
*
* @param text the initial content
*/
private StringTextStore(String text) {
super();
fText= text != null ? text : ""; //$NON-NLS-1$
fCopyLimit= fText.length() > SMALL_TEXT_LIMIT ? fText.length() / 2 : 0;
}
@Override
public char get(int offset) {
return fText.charAt(offset);
}
@Override
public String get(int offset, int length) {
if (length < fCopyLimit) {
// create a copy to avoid sharing of contained char[] - bug 292664
return new String(fText.substring(offset, offset + length).toCharArray());
}
return fText.substring(offset, offset + length);
}
@Override
public int getLength() {
return fText.length();
}
@Override
public void replace(int offset, int length, String text) {
// modification not supported
throw new UnsupportedOperationException();
}
@Override
public void set(String text) {
// modification not supported
throw new UnsupportedOperationException();
}
}
/** The underlying "real" text store */
protected ITextStore fTextStore= new StringTextStore();
/** A modifiable <code>ITextStore</code> instance */
private final ITextStore fModifiableTextStore;
/**
* Creates an empty text store. The given text store will be used upon first modification
* attempt.
*
* @param modifiableTextStore a modifiable <code>ITextStore</code> instance, may not be
* <code>null</code>
*/
public CopyOnWriteTextStore(ITextStore modifiableTextStore) {
Assert.isNotNull(modifiableTextStore);
fTextStore= new StringTextStore();
fModifiableTextStore= modifiableTextStore;
}
@Override
public char get(int offset) {
return fTextStore.get(offset);
}
@Override
public String get(int offset, int length) {
return fTextStore.get(offset, length);
}
@Override
public int getLength() {
return fTextStore.getLength();
}
@Override
public void replace(int offset, int length, String text) {
if (fTextStore != fModifiableTextStore) {
String content= fTextStore.get(0, fTextStore.getLength());
fTextStore= fModifiableTextStore;
fTextStore.set(content);
}
fTextStore.replace(offset, length, text);
}
@Override
public void set(String text) {
fTextStore= new StringTextStore(text);
fModifiableTextStore.set(""); //$NON-NLS-1$
}
}
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