/Users/parrt/antlr/code/antlr/main/runtime/Java/src/org/antlr/runtime/Lexer.java

Go to the documentation of this file.

/*
 [The "BSD licence"]
 Copyright (c) 2005-2008 Terence Parr
 All rights reserved.

 Redistribution and use in source and binary forms, with or without
 modification, are permitted provided that the following conditions
 are met:
 1. Redistributions of source code must retain the above copyright
    notice, this list of conditions and the following disclaimer.
 2. Redistributions in binary form must reproduce the above copyright
    notice, this list of conditions and the following disclaimer in the
    documentation and/or other materials provided with the distribution.
 3. The name of the author may not be used to endorse or promote products
    derived from this software without specific prior written permission.

 THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
 IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
 OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
 IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
 INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
 NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
 DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
 THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
 (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
 THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
*/
package org.antlr.runtime;

public abstract class Lexer extends BaseRecognizer implements TokenSource {
        protected CharStream input;

        public Lexer() {
        }

        public Lexer(CharStream input) {
                this.input = input;
        }

        public Lexer(CharStream input, RecognizerSharedState state) {
                super(state);
                this.input = input;
        }

        public void reset() {
                super.reset(); // reset all recognizer state variables
                // wack Lexer state variables
                if ( input!=null ) {
                        input.seek(0); // rewind the input
                }
                if ( state==null ) {
                        return; // no shared state work to do
                }
                state.token = null;
                state.type = Token.INVALID_TOKEN_TYPE;
                state.channel = Token.DEFAULT_CHANNEL;
                state.tokenStartCharIndex = -1;
                state.tokenStartCharPositionInLine = -1;
                state.tokenStartLine = -1;
                state.text = null;
        }

        public Token nextToken() {
                while (true) {
                        state.token = null;
                        state.channel = Token.DEFAULT_CHANNEL;
                        state.tokenStartCharIndex = input.index();
                        state.tokenStartCharPositionInLine = input.getCharPositionInLine();
                        state.tokenStartLine = input.getLine();
                        state.text = null;
                        if ( input.LA(1)==CharStream.EOF ) {
                                return Token.EOF_TOKEN;
                        }
                        try {
                                mTokens();
                                if ( state.token==null ) {
                                        emit();
                                }
                                else if ( state.token==Token.SKIP_TOKEN ) {
                                        continue;
                                }
                                return state.token;
                        }
                        catch (NoViableAltException nva) {
                                reportError(nva);
                                recover(nva); // throw out current char and try again
                        }
                        catch (RecognitionException re) {
                                reportError(re);
                                // match() routine has already called recover()
                        }
                }
        }

        public void skip() {
                state.token = Token.SKIP_TOKEN;
        }

        public abstract void mTokens() throws RecognitionException;

        public void setCharStream(CharStream input) {
                this.input = null;
                reset();
                this.input = input;
        }

        public CharStream getCharStream() {
                return this.input;
        }

        public String getSourceName() {
                return input.getSourceName();
        }

        public void emit(Token token) {
                state.token = token;
        }

        public Token emit() {
                Token t = new CommonToken(input, state.type, state.channel, state.tokenStartCharIndex, getCharIndex()-1);
                t.setLine(state.tokenStartLine);
                t.setText(state.text);
                t.setCharPositionInLine(state.tokenStartCharPositionInLine);
                emit(t);
                return t;
        }

        public void match(String s) throws MismatchedTokenException {
                int i = 0;
                while ( i<s.length() ) {
                        if ( input.LA(1)!=s.charAt(i) ) {
                                if ( state.backtracking>0 ) {
                                        state.failed = true;
                                        return;
                                }
                                MismatchedTokenException mte =
                                        new MismatchedTokenException(s.charAt(i), input);
                                recover(mte);
                                throw mte;
                        }
                        i++;
                        input.consume();
                        state.failed = false;
                }
        }

        public void matchAny() {
                input.consume();
        }

        public void match(int c) throws MismatchedTokenException {
                if ( input.LA(1)!=c ) {
                        if ( state.backtracking>0 ) {
                                state.failed = true;
                                return;
                        }
                        MismatchedTokenException mte =
                                new MismatchedTokenException(c, input);
                        recover(mte);  // don't really recover; just consume in lexer
                        throw mte;
                }
                input.consume();
                state.failed = false;
        }

        public void matchRange(int a, int b)
                throws MismatchedRangeException
        {
                if ( input.LA(1)<a || input.LA(1)>b ) {
                        if ( state.backtracking>0 ) {
                                state.failed = true;
                                return;
                        }
                        MismatchedRangeException mre =
                                new MismatchedRangeException(a,b,input);
                        recover(mre);
                        throw mre;
                }
                input.consume();
                state.failed = false;
        }

        public int getLine() {
                return input.getLine();
        }

        public int getCharPositionInLine() {
                return input.getCharPositionInLine();
        }

        public int getCharIndex() {
                return input.index();
        }

        public String getText() {
                if ( state.text!=null ) {
                        return state.text;
                }
                return input.substring(state.tokenStartCharIndex,getCharIndex()-1);
        }

        public void setText(String text) {
                state.text = text;
        }

        public void reportError(RecognitionException e) {
                displayRecognitionError(this.getTokenNames(), e);
        }

        public String getErrorMessage(RecognitionException e, String[] tokenNames) {
                String msg = null;
                if ( e instanceof MismatchedTokenException ) {
                        MismatchedTokenException mte = (MismatchedTokenException)e;
                        msg = "mismatched character "+getCharErrorDisplay(e.c)+" expecting "+getCharErrorDisplay(mte.expecting);
                }
                else if ( e instanceof NoViableAltException ) {
                        NoViableAltException nvae = (NoViableAltException)e;
                        // for development, can add "decision=<<"+nvae.grammarDecisionDescription+">>"
                        // and "(decision="+nvae.decisionNumber+") and
                        // "state "+nvae.stateNumber
                        msg = "no viable alternative at character "+getCharErrorDisplay(e.c);
                }
                else if ( e instanceof EarlyExitException ) {
                        EarlyExitException eee = (EarlyExitException)e;
                        // for development, can add "(decision="+eee.decisionNumber+")"
                        msg = "required (...)+ loop did not match anything at character "+getCharErrorDisplay(e.c);
                }
                else if ( e instanceof MismatchedNotSetException ) {
                        MismatchedNotSetException mse = (MismatchedNotSetException)e;
                        msg = "mismatched character "+getCharErrorDisplay(e.c)+" expecting set "+mse.expecting;
                }
                else if ( e instanceof MismatchedSetException ) {
                        MismatchedSetException mse = (MismatchedSetException)e;
                        msg = "mismatched character "+getCharErrorDisplay(e.c)+" expecting set "+mse.expecting;
                }
                else if ( e instanceof MismatchedRangeException ) {
                        MismatchedRangeException mre = (MismatchedRangeException)e;
                        msg = "mismatched character "+getCharErrorDisplay(e.c)+" expecting set "+
                                  getCharErrorDisplay(mre.a)+".."+getCharErrorDisplay(mre.b);
                }
                else {
                        msg = super.getErrorMessage(e, tokenNames);
                }
                return msg;
        }

        public String getCharErrorDisplay(int c) {
                String s = String.valueOf((char)c);
                switch ( c ) {
                        case Token.EOF :
                                s = "<EOF>";
                                break;
                        case '\n' :
                                s = "\\n";
                                break;
                        case '\t' :
                                s = "\\t";
                                break;
                        case '\r' :
                                s = "\\r";
                                break;
                }
                return "'"+s+"'";
        }

        public void recover(RecognitionException re) {
                //System.out.println("consuming char "+(char)input.LA(1)+" during recovery");
                //re.printStackTrace();
                input.consume();
        }

        public void traceIn(String ruleName, int ruleIndex)  {
                String inputSymbol = ((char)input.LT(1))+" line="+getLine()+":"+getCharPositionInLine();
                super.traceIn(ruleName, ruleIndex, inputSymbol);
        }

        public void traceOut(String ruleName, int ruleIndex)  {
                String inputSymbol = ((char)input.LT(1))+" line="+getLine()+":"+getCharPositionInLine();
                super.traceOut(ruleName, ruleIndex, inputSymbol);
        }
}

---