parser.java

java中比较著名的js引擎当属mozilla开源的rhino

/* -*- Mode: java; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 4 -*-
 *
 * ***** BEGIN LICENSE BLOCK *****
 * Version: MPL 1.1/GPL 2.0
 *
 * The contents of this file are subject to the Mozilla Public License Version
 * 1.1 (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.mozilla.org/MPL/
 *
 * Software distributed under the License is distributed on an "AS IS" basis,
 * WITHOUT WARRANTY OF ANY KIND, either express or implied. See the License
 * for the specific language governing rights and limitations under the
 * License.
 *
 * The Original Code is Rhino code, released
 * May 6, 1999.
 *
 * The Initial Developer of the Original Code is
 * Netscape Communications Corporation.
 * Portions created by the Initial Developer are Copyright (C) 1997-1999
 * the Initial Developer. All Rights Reserved.
 *
 * Contributor(s):
 *   Mike Ang
 *   Igor Bukanov
 *   Yuh-Ruey Chen
 *   Ethan Hugg
 *   Terry Lucas
 *   Mike McCabe
 *   Milen Nankov
 *
 * Alternatively, the contents of this file may be used under the terms of
 * the GNU General Public License Version 2 or later (the "GPL"), in which
 * case the provisions of the GPL are applicable instead of those above. If
 * you wish to allow use of your version of this file only under the terms of
 * the GPL and not to allow others to use your version of this file under the
 * MPL, indicate your decision by deleting the provisions above and replacing
 * them with the notice and other provisions required by the GPL. If you do
 * not delete the provisions above, a recipient may use your version of this
 * file under either the MPL or the GPL.
 *
 * ***** END LICENSE BLOCK ***** */

package org.mozilla.javascript;

import java.io.Reader;
import java.io.IOException;
import java.util.Hashtable;

/**
 * This class implements the JavaScript parser.
 *
 * It is based on the C source files jsparse.c and jsparse.h
 * in the jsref package.
 *
 * @see TokenStream
 *
 * @author Mike McCabe
 * @author Brendan Eich
 */

public class Parser
{
    // TokenInformation flags : currentFlaggedToken stores them together
    // with token type
    final static int
        CLEAR_TI_MASK  = 0xFFFF,   // mask to clear token information bits
        TI_AFTER_EOL   = 1 << 16,  // first token of the source line
        TI_CHECK_LABEL = 1 << 17;  // indicates to check for label

    CompilerEnvirons compilerEnv;
    private ErrorReporter errorReporter;
    private String sourceURI;
    boolean calledByCompileFunction;

    private TokenStream ts;
    private int currentFlaggedToken;
    private int syntaxErrorCount;

    private IRFactory nf;

    private int nestingOfFunction;

    private Decompiler decompiler;
    private String encodedSource;

// The following are per function variables and should be saved/restored
// during function parsing.
// XXX Move to separated class?
    ScriptOrFnNode currentScriptOrFn;
    private int nestingOfWith;
    private Hashtable labelSet; // map of label names into nodes
    private ObjArray loopSet;
    private ObjArray loopAndSwitchSet;
// end of per function variables

    // Exception to unwind
    private static class ParserException extends RuntimeException
    {
        static final long serialVersionUID = 5882582646773765630L;
    }

    public Parser(CompilerEnvirons compilerEnv, ErrorReporter errorReporter)
    {
        this.compilerEnv = compilerEnv;
        this.errorReporter = errorReporter;
    }

    protected Decompiler createDecompiler(CompilerEnvirons compilerEnv)
    {
        return new Decompiler();
    }

    void addWarning(String messageId, String messageArg)
    {
        String message = ScriptRuntime.getMessage1(messageId, messageArg);
        errorReporter.warning(message, sourceURI, ts.getLineno(),
                              ts.getLine(), ts.getOffset());
    }

    void addError(String messageId)
    {
        ++syntaxErrorCount;
        String message = ScriptRuntime.getMessage0(messageId);
        errorReporter.error(message, sourceURI, ts.getLineno(),
                            ts.getLine(), ts.getOffset());
    }

    RuntimeException reportError(String messageId)
    {
        addError(messageId);

        // Throw a ParserException exception to unwind the recursive descent
        // parse.
        throw new ParserException();
    }

    private int peekToken()
        throws IOException
    {
        int tt = currentFlaggedToken;
        if (tt == Token.EOF) {
            tt = ts.getToken();
            if (tt == Token.EOL) {
                do {
                    tt = ts.getToken();
                } while (tt == Token.EOL);
                tt |= TI_AFTER_EOL;
            }
            currentFlaggedToken = tt;
        }
        return tt & CLEAR_TI_MASK;
    }

    private int peekFlaggedToken()
        throws IOException
    {
        peekToken();
        return currentFlaggedToken;
    }

    private void consumeToken()
    {
        currentFlaggedToken = Token.EOF;
    }

    private int nextToken()
        throws IOException
    {
        int tt = peekToken();
        consumeToken();
        return tt;
    }

    private int nextFlaggedToken()
        throws IOException
    {
        peekToken();
        int ttFlagged = currentFlaggedToken;
        consumeToken();
        return ttFlagged;
    }

    private boolean matchToken(int toMatch)
        throws IOException
    {
        int tt = peekToken();
        if (tt != toMatch) {
            return false;
        }
        consumeToken();
        return true;
    }

    private int peekTokenOrEOL()
        throws IOException
    {
        int tt = peekToken();
        // Check for last peeked token flags
        if ((currentFlaggedToken & TI_AFTER_EOL) != 0) {
            tt = Token.EOL;
        }
        return tt;
    }

    private void setCheckForLabel()
    {
        if ((currentFlaggedToken & CLEAR_TI_MASK) != Token.NAME)
            throw Kit.codeBug();
        currentFlaggedToken |= TI_CHECK_LABEL;
    }

    private void mustMatchToken(int toMatch, String messageId)
        throws IOException, ParserException
    {
        if (!matchToken(toMatch)) {
            reportError(messageId);
        }
    }

    private void mustHaveXML()
    {
        if (!compilerEnv.isXmlAvailable()) {
            reportError("msg.XML.not.available");
        }
    }

    public String getEncodedSource()
    {
        return encodedSource;
    }

    public boolean eof()
    {
        return ts.eof();
    }

    boolean insideFunction()
    {
        return nestingOfFunction != 0;
    }

    private Node enterLoop(Node loopLabel)
    {
        Node loop = nf.createLoopNode(loopLabel, ts.getLineno());
        if (loopSet == null) {
            loopSet = new ObjArray();
            if (loopAndSwitchSet == null) {
                loopAndSwitchSet = new ObjArray();
            }
        }
        loopSet.push(loop);
        loopAndSwitchSet.push(loop);
        return loop;
    }

    private void exitLoop()
    {
        loopSet.pop();
        loopAndSwitchSet.pop();
    }

    private Node enterSwitch(Node switchSelector, int lineno, Node switchLabel)
    {
        Node switchNode = nf.createSwitch(switchSelector, lineno);
        if (loopAndSwitchSet == null) {
            loopAndSwitchSet = new ObjArray();
        }
        loopAndSwitchSet.push(switchNode);
        return switchNode;
    }

    private void exitSwitch()
    {
        loopAndSwitchSet.pop();
    }

    /*
     * Build a parse tree from the given sourceString.
     *
     * @return an Object representing the parsed
     * program.  If the parse fails, null will be returned.  (The
     * parse failure will result in a call to the ErrorReporter from
     * CompilerEnvirons.)
     */
    public ScriptOrFnNode parse(String sourceString,
                                String sourceURI, int lineno)
    {
        this.sourceURI = sourceURI;
        this.ts = new TokenStream(this, null, sourceString, lineno);
        try {
            return parse();
        } catch (IOException ex) {
            // Should never happen
            throw new IllegalStateException();
        }
    }

    /*
     * Build a parse tree from the given sourceString.
     *
     * @return an Object representing the parsed
     * program.  If the parse fails, null will be returned.  (The
     * parse failure will result in a call to the ErrorReporter from
     * CompilerEnvirons.)
     */
    public ScriptOrFnNode parse(Reader sourceReader,
                                String sourceURI, int lineno)
        throws IOException
    {
        this.sourceURI = sourceURI;
        this.ts = new TokenStream(this, sourceReader, null, lineno);
        return parse();
    }

    private ScriptOrFnNode parse()
        throws IOException
    {
        this.decompiler = createDecompiler(compilerEnv);
        this.nf = new IRFactory(this);
        currentScriptOrFn = nf.createScript();
        int sourceStartOffset = decompiler.getCurrentOffset();
        this.encodedSource = null;
        decompiler.addToken(Token.SCRIPT);

        this.currentFlaggedToken = Token.EOF;
        this.syntaxErrorCount = 0;

        int baseLineno = ts.getLineno();  // line number where source starts

        /* so we have something to add nodes to until
         * we've collected all the source */
        Node pn = nf.createLeaf(Token.BLOCK);

        try {
            for (;;) {
                int tt = peekToken();

                if (tt <= Token.EOF) {
                    break;
                }

                Node n;
                if (tt == Token.FUNCTION) {
                    consumeToken();
                    try {
                        n = function(calledByCompileFunction
                                     ? FunctionNode.FUNCTION_EXPRESSION
                                     : FunctionNode.FUNCTION_STATEMENT);
                    } catch (ParserException e) {
                        break;
                    }
                } else {
                    n = statement();
                }
                nf.addChildToBack(pn, n);
            }
        } catch (StackOverflowError ex) {
            String msg = ScriptRuntime.getMessage0(
                "mag.too.deep.parser.recursion");
            throw Context.reportRuntimeError(msg, sourceURI,
                                             ts.getLineno(), null, 0);
        }

        if (this.syntaxErrorCount != 0) {
            String msg = String.valueOf(this.syntaxErrorCount);
            msg = ScriptRuntime.getMessage1("msg.got.syntax.errors", msg);
            throw errorReporter.runtimeError(msg, sourceURI, baseLineno,
                                             null, 0);
        }

        currentScriptOrFn.setSourceName(sourceURI);
        currentScriptOrFn.setBaseLineno(baseLineno);
        currentScriptOrFn.setEndLineno(ts.getLineno());

        int sourceEndOffset = decompiler.getCurrentOffset();
        currentScriptOrFn.setEncodedSourceBounds(sourceStartOffset,
                                                 sourceEndOffset);

        nf.initScript(currentScriptOrFn, pn);

        if (compilerEnv.isGeneratingSource()) {
            encodedSource = decompiler.getEncodedSource();
        }
        this.decompiler = null; // It helps GC

        return currentScriptOrFn;
    }

    /*
     * The C version of this function takes an argument list,
     * which doesn't seem to be needed for tree generation...
     * it'd only be useful for checking argument hiding, which
     * I'm not doing anyway...
     */
    private Node parseFunctionBody()
        throws IOException
    {
        ++nestingOfFunction;
        Node pn = nf.createBlock(ts.getLineno());
        try {
            bodyLoop: for (;;) {
                Node n;
                int tt = peekToken();