Copyright (c) 2000, 2007 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:
    IBM Corporation - initial API and implementation
/*******************************************************************************
 * Copyright (c) 2000, 2007 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:
 *     IBM Corporation - initial API and implementation
 *******************************************************************************/
package org.eclipse.core.internal.filebuffers;

import java.io.IOException;
import java.io.Reader;

import org.eclipse.core.runtime.Assert;

import org.eclipse.jface.text.BadLocationException;
import org.eclipse.jface.text.DocumentEvent;
import org.eclipse.jface.text.IDocument;
import org.eclipse.jface.text.IDocumentListener;


A Reader that reads from an IDocument.
The reader ensures that its content is the same as the document
content when the stream was created.
 Note that close() must be called to release any acquired resources. 
Since:
3.1/**
 * A <code>Reader</code> that reads from an <code>IDocument</code>.
 * The reader ensures that its content is the same as the document
 * content when the stream was created.
 * <p>
 * Note that {@link #close()} must be called to release any acquired
 * resources.
 * </p>
 *
 * @since 3.1
 */
class DocumentReader extends Reader {

	
Document based character sequence.
/**
	 * Document based character sequence.
	 */
	private static class DocumentCharSequence implements CharSequence {

		
Document /** Document */
		private IDocument fDocument;

		
Initialize with the sequence of characters in the given
document.
Params:
document – the document/**
		 * Initialize with the sequence of characters in the given
		 * document.
		 *
		 * @param document the document
		 */
		public DocumentCharSequence(IDocument document) {
			fDocument= document;
		}

		@Override
		public int length() {
			return fDocument.getLength();
		}

		@Override
		public char charAt(int index) {
			try {
				return fDocument.getChar(index);
			} catch (BadLocationException x) {
				throw new IndexOutOfBoundsException(x.getLocalizedMessage());
			}
		}

		@Override
		public CharSequence subSequence(int start, int end) {
			try {
				return fDocument.get(start, end - start);
			} catch (BadLocationException x) {
				throw new IndexOutOfBoundsException(x.getLocalizedMessage());
			}
		}
	}

	
Internal document listener.
/**
	 * Internal document listener.
	 */
	private class InternalDocumentListener implements IDocumentListener {

		@Override
		public void documentAboutToBeChanged(DocumentEvent event) {
			handleDocumentAboutToBeChanged();
		}

		@Override
		public void documentChanged(DocumentEvent event) {
		}
	}

	
The character sequence. /** The character sequence. */
	private volatile CharSequence fCharSequence;

	
Document length. /** Document length. */
	private int fLength;

	
The current offset. /** The current offset. */
	private int fOffset= 0;

	
The document. /** The document. */
	private IDocument fDocument;

	
The document listener. /** The document listener. */
	private IDocumentListener fDocumentListener= new InternalDocumentListener();

	
Creates a new document input stream and initializes
the stream to read from the given document.
Params:
document – the document/**
	 * Creates a new document input stream and initializes
	 * the stream to read from the given document.
	 *
	 * @param document the document
	 */
	public DocumentReader(IDocument document) {
		Assert.isNotNull(document);
		fDocument= document;
		fCharSequence= new DocumentCharSequence(fDocument);
		fDocument.addDocumentListener(fDocumentListener);
		fLength= fCharSequence.length();
	}

	@Override
	public void close() {
		synchronized (this) {
			fCharSequence= null;
		}
		releaseDocument();
	}

	
Copies the document prior to modification and removes the document listener.
/**
	 * Copies the document prior to modification and removes the document listener.
	 */
	private void handleDocumentAboutToBeChanged() {
		IDocument document= fDocument;
		if (fCharSequence == null || document == null)
			return;
		String content= document.get();
		synchronized (this) {
			if (fCharSequence == null)
				return;
			fCharSequence= content;
		}
		releaseDocument();
	}

	
Removes the document listener.
/**
	 * Removes the document listener.
	 */
	private synchronized void releaseDocument() {
		if (fDocument != null)
			fDocument.removeDocumentListener(fDocumentListener);
		fDocument= null;
		fDocumentListener= null;
	}

	@Override
	public int read(char[] cbuf, int off, int len) throws IOException {
		int i= 0;
		try {
			for (; i < len && fOffset < fLength; i++)
				cbuf[off + i]=  fCharSequence.charAt(fOffset++);
			if (i > 0)
				return i;

			return -1;
		} catch (NullPointerException x) {
			throw new IOException(FileBuffersMessages.DocumentInputStream_error_streamClosed);
		} catch (IndexOutOfBoundsException x) {
			return i-1;
		}
	}
}