parser.java

java中比较著名的js引擎当属mozilla开源的rhino

                switch (tt) {
                  case Token.ERROR:
                  case Token.EOF:
                  case Token.RC:
                    break bodyLoop;

                  case Token.FUNCTION:
                    consumeToken();
                    n = function(FunctionNode.FUNCTION_STATEMENT);
                    break;
                  default:
                    n = statement();
                    break;
                }
                nf.addChildToBack(pn, n);
            }
        } catch (ParserException e) {
            // Ignore it
        } finally {
            --nestingOfFunction;
        }

        return pn;
    }

    private Node function(int functionType)
        throws IOException, ParserException
    {
        int syntheticType = functionType;
        int baseLineno = ts.getLineno();  // line number where source starts

        int functionSourceStart = decompiler.markFunctionStart(functionType);
        String name;
        Node memberExprNode = null;
        if (matchToken(Token.NAME)) {
            name = ts.getString();
            decompiler.addName(name);
            if (!matchToken(Token.LP)) {
                if (compilerEnv.isAllowMemberExprAsFunctionName()) {
                    // Extension to ECMA: if 'function <name>' does not follow
                    // by '(', assume <name> starts memberExpr
                    Node memberExprHead = nf.createName(name);
                    name = "";
                    memberExprNode = memberExprTail(false, memberExprHead);
                }
                mustMatchToken(Token.LP, "msg.no.paren.parms");
            }
        } else if (matchToken(Token.LP)) {
            // Anonymous function
            name = "";
        } else {
            name = "";
            if (compilerEnv.isAllowMemberExprAsFunctionName()) {
                // Note that memberExpr can not start with '(' like
                // in function (1+2).toString(), because 'function (' already
                // processed as anonymous function
                memberExprNode = memberExpr(false);
            }
            mustMatchToken(Token.LP, "msg.no.paren.parms");
        }

        if (memberExprNode != null) {
            syntheticType = FunctionNode.FUNCTION_EXPRESSION;
        }

        boolean nested = insideFunction();

        FunctionNode fnNode = nf.createFunction(name);
        if (nested || nestingOfWith > 0) {
            // 1. Nested functions are not affected by the dynamic scope flag
            // as dynamic scope is already a parent of their scope.
            // 2. Functions defined under the with statement also immune to
            // this setup, in which case dynamic scope is ignored in favor
            // of with object.
            fnNode.itsIgnoreDynamicScope = true;
        }

        int functionIndex = currentScriptOrFn.addFunction(fnNode);

        int functionSourceEnd;

        ScriptOrFnNode savedScriptOrFn = currentScriptOrFn;
        currentScriptOrFn = fnNode;
        int savedNestingOfWith = nestingOfWith;
        nestingOfWith = 0;
        Hashtable savedLabelSet = labelSet;
        labelSet = null;
        ObjArray savedLoopSet = loopSet;
        loopSet = null;
        ObjArray savedLoopAndSwitchSet = loopAndSwitchSet;
        loopAndSwitchSet = null;

        Node body;
        String source;
        try {
            decompiler.addToken(Token.LP);
            if (!matchToken(Token.RP)) {
                boolean first = true;
                do {
                    if (!first)
                        decompiler.addToken(Token.COMMA);
                    first = false;
                    mustMatchToken(Token.NAME, "msg.no.parm");
                    String s = ts.getString();
                    if (fnNode.hasParamOrVar(s)) {
                        addWarning("msg.dup.parms", s);
                    }
                    fnNode.addParam(s);
                    decompiler.addName(s);
                } while (matchToken(Token.COMMA));

                mustMatchToken(Token.RP, "msg.no.paren.after.parms");
            }
            decompiler.addToken(Token.RP);

            mustMatchToken(Token.LC, "msg.no.brace.body");
            decompiler.addEOL(Token.LC);
            body = parseFunctionBody();
            mustMatchToken(Token.RC, "msg.no.brace.after.body");

            decompiler.addToken(Token.RC);
            functionSourceEnd = decompiler.markFunctionEnd(functionSourceStart);
            if (functionType != FunctionNode.FUNCTION_EXPRESSION) {
                 if (compilerEnv.getLanguageVersion() >= Context.VERSION_1_2) {
                    // function f() {} function g() {} is not allowed in 1.2
                    // or later but for compatibility with old scripts
                    // the check is done only if language is
                    // explicitly set.
                    //  XXX warning needed if version == VERSION_DEFAULT ?
                    int tt = peekTokenOrEOL();
                    if (tt == Token.FUNCTION) {
                         reportError("msg.no.semi.stmt");
                    }
                 }
                // Add EOL only if function is not part of expression
                // since it gets SEMI + EOL from Statement in that case
                decompiler.addToken(Token.EOL);
            }
        }
        finally {
            loopAndSwitchSet = savedLoopAndSwitchSet;
            loopSet = savedLoopSet;
            labelSet = savedLabelSet;
            nestingOfWith = savedNestingOfWith;
            currentScriptOrFn = savedScriptOrFn;
        }

        fnNode.setEncodedSourceBounds(functionSourceStart, functionSourceEnd);
        fnNode.setSourceName(sourceURI);
        fnNode.setBaseLineno(baseLineno);
        fnNode.setEndLineno(ts.getLineno());

        Node pn = nf.initFunction(fnNode, functionIndex, body, syntheticType);
        if (memberExprNode != null) {
            pn = nf.createAssignment(Token.ASSIGN, memberExprNode, pn);
            if (functionType != FunctionNode.FUNCTION_EXPRESSION) {
                // XXX check JScript behavior: should it be createExprStatement?
                pn = nf.createExprStatementNoReturn(pn, baseLineno);
            }
        }
        return pn;
    }

    private Node statements()
        throws IOException
    {
        Node pn = nf.createBlock(ts.getLineno());

        int tt;
        while((tt = peekToken()) > Token.EOF && tt != Token.RC) {
            nf.addChildToBack(pn, statement());
        }

        return pn;
    }

    private Node condition()
        throws IOException, ParserException
    {
        Node pn;
        mustMatchToken(Token.LP, "msg.no.paren.cond");
        decompiler.addToken(Token.LP);
        pn = expr(false);
        mustMatchToken(Token.RP, "msg.no.paren.after.cond");
        decompiler.addToken(Token.RP);

        // there's a check here in jsparse.c that corrects = to ==

        return pn;
    }

    // match a NAME; return null if no match.
    private Node matchJumpLabelName()
        throws IOException, ParserException
    {
        Node label = null;

        int tt = peekTokenOrEOL();
        if (tt == Token.NAME) {
            consumeToken();
            String name = ts.getString();
            decompiler.addName(name);
            if (labelSet != null) {
                label = (Node)labelSet.get(name);
            }
            if (label == null) {
                reportError("msg.undef.label");
            }
        }

        return label;
    }

    private Node statement()
        throws IOException
    {
        try {
            Node pn = statementHelper(null);
            if (pn != null) {
                return pn;
            }
        } catch (ParserException e) { }

        // skip to end of statement
        int lineno = ts.getLineno();
        guessingStatementEnd: for (;;) {
            int tt = peekTokenOrEOL();
            consumeToken();
            switch (tt) {
              case Token.ERROR:
              case Token.EOF:
              case Token.EOL:
              case Token.SEMI:
                break guessingStatementEnd;
            }
        }
        return nf.createExprStatement(nf.createName("error"), lineno);
    }

    /**
     * Whether the "catch (e: e instanceof Exception) { ... }" syntax
     * is implemented.
     */

    private Node statementHelper(Node statementLabel)
        throws IOException, ParserException
    {
        Node pn = null;

        int tt;

        tt = peekToken();

        switch(tt) {
          case Token.IF: {
            consumeToken();

            decompiler.addToken(Token.IF);
            int lineno = ts.getLineno();
            Node cond = condition();
            decompiler.addEOL(Token.LC);
            Node ifTrue = statement();
            Node ifFalse = null;
            if (matchToken(Token.ELSE)) {
                decompiler.addToken(Token.RC);
                decompiler.addToken(Token.ELSE);
                decompiler.addEOL(Token.LC);
                ifFalse = statement();
            }
            decompiler.addEOL(Token.RC);
            pn = nf.createIf(cond, ifTrue, ifFalse, lineno);
            return pn;
          }

          case Token.SWITCH: {
            consumeToken();

            decompiler.addToken(Token.SWITCH);
            int lineno = ts.getLineno();
            mustMatchToken(Token.LP, "msg.no.paren.switch");
            decompiler.addToken(Token.LP);
            pn = enterSwitch(expr(false), lineno, statementLabel);
            try {
                mustMatchToken(Token.RP, "msg.no.paren.after.switch");
                decompiler.addToken(Token.RP);
                mustMatchToken(Token.LC, "msg.no.brace.switch");
                decompiler.addEOL(Token.LC);

                boolean hasDefault = false;
                switchLoop: for (;;) {
                    tt = nextToken();
                    Node caseExpression;
                    switch (tt) {
                      case Token.RC:
                        break switchLoop;

                      case Token.CASE:
                        decompiler.addToken(Token.CASE);
                        caseExpression = expr(false);
                        mustMatchToken(Token.COLON, "msg.no.colon.case");
                        decompiler.addEOL(Token.COLON);
                        break;

                      case Token.DEFAULT:
                        if (hasDefault) {
                            reportError("msg.double.switch.default");
                        }
                        decompiler.addToken(Token.DEFAULT);
                        hasDefault = true;
                        caseExpression = null;
                        mustMatchToken(Token.COLON, "msg.no.colon.case");
                        decompiler.addEOL(Token.COLON);
                        break;

                      default:
                        reportError("msg.bad.switch");
                        break switchLoop;
                    }

                    Node block = nf.createLeaf(Token.BLOCK);
                    while ((tt = peekToken()) != Token.RC
                           && tt != Token.CASE
                           && tt != Token.DEFAULT
                           && tt != Token.EOF)
                    {
                        nf.addChildToBack(block, statement());
                    }

                    // caseExpression == null => add default lable
                    nf.addSwitchCase(pn, caseExpression, block);
                }
                decompiler.addEOL(Token.RC);
                nf.closeSwitch(pn);
            } finally {
                exitSwitch();
            }
            return pn;
          }

          case Token.WHILE: {
            consumeToken();
            decompiler.addToken(Token.WHILE);

            Node loop = enterLoop(statementLabel);
            try {
                Node cond = condition();
                decompiler.addEOL(Token.LC);
                Node body = statement();
                decompiler.addEOL(Token.RC);
                pn = nf.createWhile(loop, cond, body);
            } finally {
                exitLoop();
            }
            return pn;
          }

          case Token.DO: {
            consumeToken();
            decompiler.addToken(Token.DO);
            decompiler.addEOL(Token.LC);

            Node loop = enterLoop(statementLabel);
            try {
                Node body = statement();
                decompiler.addToken(Token.RC);
                mustMatchToken(Token.WHILE, "msg.no.while.do");
                decompiler.addToken(Token.WHILE);
                Node cond = condition();
                pn = nf.createDoWhile(loop, body, cond);
            } finally {
                exitLoop();
            }
            // Always auto-insert semicon to follow SpiderMonkey:
            // It is required by EMAScript but is ignored by the rest of
            // world, see bug 238945
            matchToken(Token.SEMI);
            decompiler.addEOL(Token.SEMI);
            return pn;
          }

          case Token.FOR: {
            consumeToken();
            boolean isForEach = false;
            decompiler.addToken(Token.FOR);

            Node loop = enterLoop(statementLabel);
            try {

                Node init;  // Node init is also foo in 'foo in Object'
                Node cond;  // Node cond is also object in 'foo in Object'
                Node incr = null; // to kill warning
                Node body;

                // See if this is a for each () instead of just a for ()
                if (matchToken(Token.NAME)) {
                    decompiler.addName(ts.getString());
                    if (ts.getString().equals("each")) {
                        isForEach = true;
                    } else {
                        reportError("msg.no.paren.for");
                    }
                }

                mustMatchToken(Token.LP, "msg.no.paren.for");
                decompiler.addToken(Token.LP);