org.apache.jena.riot.lang.LangEngine Maven / Gradle / Ivy

Show more of this group Show more artifacts with this name
Show all versions of jena-arq Show documentation
ARQ is a SPARQL 1.1 query engine for Apache Jena
There is a newer version: 5.0.0
/*
 * Licensed to the Apache Software Foundation (ASF) under one
 * or more contributor license agreements.  See the NOTICE file
 * distributed with this work for additional information
 * regarding copyright ownership.  The ASF licenses this file
 * to you under the Apache License, Version 2.0 (the
 * "License"); you may not use this file except in compliance
 * with the License.  You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package org.apache.jena.riot.lang;

import static org.apache.jena.riot.tokens.TokenType.EOF;
import static org.apache.jena.riot.tokens.TokenType.NODE;

import java.util.Objects;

import org.apache.jena.atlas.AtlasException;
import org.apache.jena.atlas.iterator.PeekIterator;
import org.apache.jena.riot.RiotParseException;
import org.apache.jena.riot.system.ErrorHandler;
import org.apache.jena.riot.system.ParserProfile;
import org.apache.jena.riot.tokens.Token;
import org.apache.jena.riot.tokens.TokenType;
import org.apache.jena.riot.tokens.Tokenizer;

/** Common operations for RIOT token stream parsing - not the implementation LangRIOT. */
public class LangEngine {
    protected ParserProfile     profile;
    protected ErrorHandler      errorHandler;
    protected final Tokenizer   tokens;
    private PeekIterator peekIter;

    protected LangEngine(Tokenizer tokens, ParserProfile profile, ErrorHandler errorHandler) {
        this.tokens = Objects.requireNonNull(tokens);
        this.profile = Objects.requireNonNull(profile);
        this.errorHandler = errorHandler;
        // The PeekIterator is always loaded with the next token until the end
        // (for simplicity) but it means this can throw an exception.
        try { this.peekIter = new PeekIterator<>(tokens); }
        catch (RiotParseException ex) { raiseException(ex); }
    }

    // ---- Managing tokens.

    protected final Token peekToken() {
        // Avoid repeating.
        if ( eof() )
            return tokenEOF;
        return peekIter.peek();
    }

    // Set when we get to EOF to record line/col of the EOF.
    private Token tokenEOF = null;

    protected final boolean eof() {
        if ( tokenEOF != null )
            return true;

        if ( !moreTokens() ) {
            tokenEOF = new Token(tokens.getLine(), tokens.getColumn());
            tokenEOF.setType(EOF);
            return true;
        }
        return false;
    }

    protected final boolean moreTokens() {
        return peekIter.hasNext();
    }

    protected final boolean lookingAt(TokenType tokenType) {
        if ( eof() )
            return tokenType == EOF;
        if ( tokenType == NODE )
            return peekToken().isNode();
        return peekToken().hasType(tokenType);
    }

    // Remember line/col of last token for messages
    protected long currLine = -1;
    protected long currCol  = -1;

    protected final Token nextToken() {
        if ( eof() )
            return tokenEOF;

        // Tokenizer errors appear here!
        try {
            Token t = peekIter.next();
            currLine = t.getLine();
            currCol = t.getColumn();
            return t;
        }
        catch (RiotParseException ex) {
            // Intercept to log it.
            raiseException(ex);
            throw ex;
        }
        catch (AtlasException ex) {
            // Bad I/O
            RiotParseException ex2 = new RiotParseException(ex.getMessage(), -1, -1);
            raiseException(ex2);
            throw ex2;
        }
    }

    protected final void expectOrEOF(String msg, TokenType tokenType) {
        if ( eof() )
            return;
        expect(msg, tokenType);
    }

    protected final void skipIf(TokenType ttype) {
        if ( lookingAt(ttype) )
            nextToken();
    }

    protected final void expect(String msg, TokenType ttype) {
        if ( !lookingAt(ttype) ) {
            Token location = peekToken();
            exception(location, msg);
        }
        nextToken();
    }

    protected final void exception(Token token, String msg, Object... args) {
        if ( token != null )
            exceptionDirect(String.format(msg, args), token.getLine(), token.getColumn());
        else
            exceptionDirect(String.format(msg, args), -1, -1);
    }

    protected final void exceptionDirect(String msg, long line, long col) {
        raiseException(new RiotParseException(msg, line, col));
    }

    protected final void raiseException(RiotParseException ex) {
        if ( errorHandler != null )
            errorHandler.fatal(ex.getOriginalMessage(), ex.getLine(), ex.getCol());
        throw ex;
    }
}