Copyright (c) 2005, 2012 IBM Corporation and others.
This program and the accompanying materials
are made available under the terms of the Eclipse Public License 2.0
which accompanies this distribution, and is available at
https://www.eclipse.org/legal/epl-2.0/
SPDX-License-Identifier: EPL-2.0
Contributors:
    Anton Leherbauer (anton.leherbauer@windriver.com) - initial API and implementation
/*******************************************************************************
 * Copyright (c) 2005, 2012 IBM Corporation and others.
 *
 * This program and the accompanying materials
 * are made available under the terms of the Eclipse Public License 2.0
 * which accompanies this distribution, and is available at
 * https://www.eclipse.org/legal/epl-2.0/
 *
 * SPDX-License-Identifier: EPL-2.0
 *
 * 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 ITextStore wrapper.

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.


This class is not intended to be subclassed.

Since:
3.2
@noextend
This class is not intended to be subclassed by clients./**
 * 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 replace a text range or set new content will throw an UnsupportedOperationException.
/**
	 * 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 /** Minimum text limit whether to enable String copying */
		private static final int SMALL_TEXT_LIMIT= 1024 * 1024;

		
Represents the content of this text store. /** Represents the content of this text store. */
		private final String fText;

		
Minimum length limit below which get(int, int) will return a String copy /** Minimum length limit below which {@link #get(int, int)} will return a String copy */
		private final int fCopyLimit;

		
Create an empty text store.
/**
		 * Create an empty text store.
		 */
		private StringTextStore() {
			this(""); //$NON-NLS-1$
		}

		
Create a text store with initial content.
Params:
text – the initial content/**
		 * 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 /** The underlying "real" text store */
	protected ITextStore fTextStore= new StringTextStore();

	
A modifiable ITextStore instance /** 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.
Params:
modifiableTextStore – a modifiable ITextStore instance, may not be
           null/**
	 * 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(""); //$NON-NLS-1$
	}

}