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/*******************************************************************************
* Copyright (c) 2000, 2004 IBM Corporation and others.
* All rights reserved. This program and the accompanying materials
* are made available under the terms of the Common Public License v1.0
* which accompanies this distribution, and is available at
* http://www.eclipse.org/legal/cpl-v10.html
*
* Contributors:
* IBM Corporation - initial API and implementation
*******************************************************************************/
package org.eclipse.jface.text.rules;
import org.eclipse.jface.text.Assert;
import org.eclipse.jface.text.BadLocationException;
import org.eclipse.jface.text.IDocument;
/**
* A generic scanner which can be "programmed" with a sequence of rules.
* The scanner is used to get the next token by evaluating its rule in sequence until
* one is successful. If a rule returns a token which is undefined, the scanner will proceed to
* the next rule. Otherwise the token provided by the rule will be returned by
* the scanner. If no rule returned a defined token, this scanner returns a token
* which returns <code>true</code> when calling <code>isOther</code>, unless the end
* of the file is reached. In this case the token returns <code>true</code> when calling
* <code>isEOF</code>.
*
* @see IRule
*/
public class RuleBasedScanner implements ICharacterScanner, ITokenScanner {
/** The list of rules of this scanner */
protected IRule[] fRules;
/** The token to be returned by default if no rule fires */
protected IToken fDefaultReturnToken;
/** The document to be scanned */
protected IDocument fDocument;
/** The cached legal line delimiters of the document */
protected char[][] fDelimiters;
/** The offset of the next character to be read */
protected int fOffset;
/** The end offset of the range to be scanned */
protected int fRangeEnd;
/** The offset of the last read token */
protected int fTokenOffset;
/** The cached column of the current scanner position */
protected int fColumn;
/** Internal setting for the uninitialized column cache. */
protected static final int UNDEFINED= -1;
/**
* Creates a new rule based scanner which does not have any rule.
*/
public RuleBasedScanner() {
}
/**
* Configures the scanner with the given sequence of rules.
*
* @param rules the sequence of rules controlling this scanner
*/
public void setRules(IRule[] rules) {
fRules= rules;
}
/**
* Configures the scanner's default return token. This is the token
* which is returned when non of the rules fired and EOF has not been
* reached.
*
* @param defaultReturnToken the default return token
* @since 2.0
*/
public void setDefaultReturnToken(IToken defaultReturnToken) {
Assert.isNotNull(defaultReturnToken.getData());
fDefaultReturnToken= defaultReturnToken;
}
/*
* @see ITokenScanner#setRange(IDocument, int, int)
*/
public void setRange(IDocument document, int offset, int length) {
fDocument= document;
fOffset= offset;
fColumn= UNDEFINED;
fRangeEnd= Math.min(fDocument.getLength(), offset + length);
String[] delimiters= fDocument.getLegalLineDelimiters();
fDelimiters= new char[delimiters.length][];
for (int i= 0; i < delimiters.length; i++)
fDelimiters[i]= delimiters[i].toCharArray();
if (fDefaultReturnToken == null)
fDefaultReturnToken= new Token(null);
}
/*
* @see ITokenScanner#getTokenOffset()
*/
public int getTokenOffset() {
return fTokenOffset;
}
/*
* @see ITokenScanner#getTokenLength()
*/
public int getTokenLength() {
if (fOffset < fRangeEnd)
return fOffset - getTokenOffset();
return fRangeEnd - getTokenOffset();
}
/*
* @see ICharacterScanner#getColumn()
*/
public int getColumn() {
if (fColumn == UNDEFINED) {
try {
int line= fDocument.getLineOfOffset(fOffset);
int start= fDocument.getLineOffset(line);
fColumn= fOffset - start;
} catch (BadLocationException ex) {
}
}
return fColumn;
}
/*
* @see ICharacterScanner#getLegalLineDelimiters()
*/
public char[][] getLegalLineDelimiters() {
return fDelimiters;
}
/*
* @see ITokenScanner#nextToken()
*/
public IToken nextToken() {
IToken token;
while (true) {
fTokenOffset= fOffset;
fColumn= UNDEFINED;
if (fRules != null) {
for (int i= 0; i < fRules.length; i++) {
token= (fRules[i].evaluate(this));
if (!token.isUndefined())
return token;
}
}
if (read() == EOF)
return Token.EOF;
else
return fDefaultReturnToken;
}
}
/*
* @see ICharacterScanner#read()
*/
public int read() {
try {
if (fOffset < fRangeEnd) {
try {
return fDocument.getChar(fOffset);
} catch (BadLocationException e) {
}
}
return EOF;
} finally {
++ fOffset;
fColumn= UNDEFINED;
}
}
/*
* @see ICharacterScanner#unread()
*/
public void unread() {
--fOffset;
}
}
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