org.eclipse.jface.text.rules.BufferedRuleBasedScanner Maven / Gradle / Ivy
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/*******************************************************************************
* Copyright (c) 2000, 2008 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.jface.text.rules;
import org.eclipse.core.runtime.Assert;
import org.eclipse.jface.text.BadLocationException;
import org.eclipse.jface.text.IDocument;
/**
* A buffered rule based scanner. The buffer always contains a section
* of a fixed size of the document to be scanned. Completely adheres to
* the contract of RuleBasedScanner
.
*
* @since 3.14
*/
public class BufferedRuleBasedScanner extends RuleBasedScanner {
/** The default buffer size. Value = 500 */
private final static int DEFAULT_BUFFER_SIZE= 500;
/** The actual size of the buffer. Initially set to DEFAULT_BUFFER_SIZE
*/
private int fBufferSize= DEFAULT_BUFFER_SIZE;
/** The buffer */
private char[] fBuffer= new char[DEFAULT_BUFFER_SIZE];
/** The offset of the document at which the buffer starts */
private int fStart;
/** The offset of the document at which the buffer ends */
private int fEnd;
/** The cached length of the document */
private int fDocumentLength;
/**
* Creates a new buffered rule based scanner which does
* not have any rule and a default buffer size of 500 characters.
*/
protected BufferedRuleBasedScanner() {
super();
}
/**
* Creates a new buffered rule based scanner which does
* not have any rule. The buffer size is set to the given
* number of characters.
*
* @param size the buffer size
*/
public BufferedRuleBasedScanner(int size) {
super();
setBufferSize(size);
}
/**
* Sets the buffer to the given number of characters.
*
* @param size the buffer size
*/
protected void setBufferSize(int size) {
Assert.isTrue(size > 0);
fBufferSize= size;
fBuffer= new char[size];
}
/**
* Shifts the buffer so that the buffer starts at the
* given document offset.
*
* @param offset the document offset at which the buffer starts
*/
private void shiftBuffer(int offset) {
fStart= offset;
fEnd= fStart + fBufferSize;
if (fEnd > fDocumentLength)
fEnd= fDocumentLength;
try {
String content= fDocument.get(fStart, fEnd - fStart);
content.getChars(0, fEnd - fStart, fBuffer, 0);
} catch (BadLocationException x) {
}
}
@Override
public void setRange(IDocument document, int offset, int length) {
super.setRange(document, offset, length);
fDocumentLength= document.getLength();
shiftBuffer(offset);
}
@Override
public int read() {
fColumn= UNDEFINED;
if (fOffset >= fRangeEnd) {
++ fOffset;
return EOF;
}
if (fOffset == fEnd)
shiftBuffer(fEnd);
else if (fOffset < fStart || fEnd < fOffset)
shiftBuffer(fOffset);
return fBuffer[fOffset++ - fStart];
}
@Override
public void unread() {
if (fOffset == fStart)
shiftBuffer(Math.max(0, fStart - (fBufferSize / 2)));
--fOffset;
fColumn= UNDEFINED;
}
}