parser.java

java中比较著名的js引擎当属mozilla开源的rhino

            if (matchToken(Token.LP)) {
                decompiler.addToken(Token.LP);
                /* Add the arguments to pn, if any are supplied. */
                argumentList(pn);
            }

            /* XXX there's a check in the C source against
             * "too many constructor arguments" - how many
             * do we claim to support?
             */

            /* Experimental syntax:  allow an object literal to follow a new expression,
             * which will mean a kind of anonymous class built with the JavaAdapter.
             * the object literal will be passed as an additional argument to the constructor.
             */
            tt = peekToken();
            if (tt == Token.LC) {
                nf.addChildToBack(pn, primaryExpr());
            }
        } else {
            pn = primaryExpr();
        }

        return memberExprTail(allowCallSyntax, pn);
    }

    private Node memberExprTail(boolean allowCallSyntax, Node pn)
        throws IOException, ParserException
    {
      tailLoop:
        for (;;) {
            int tt = peekToken();
            switch (tt) {

              case Token.DOT:
              case Token.DOTDOT:
                {
                    int memberTypeFlags;
                    String s;

                    consumeToken();
                    decompiler.addToken(tt);
                    memberTypeFlags = 0;
                    if (tt == Token.DOTDOT) {
                        mustHaveXML();
                        memberTypeFlags = Node.DESCENDANTS_FLAG;
                    }
                    if (!compilerEnv.isXmlAvailable()) {
                        mustMatchToken(Token.NAME, "msg.no.name.after.dot");
                        s = ts.getString();
                        decompiler.addName(s);
                        pn = nf.createPropertyGet(pn, null, s, memberTypeFlags);
                        break;
                    }

                    tt = nextToken();
                    switch (tt) {
                      // handles: name, ns::name, ns::*, ns::[expr]
                      case Token.NAME:
                        s = ts.getString();
                        decompiler.addName(s);
                        pn = propertyName(pn, s, memberTypeFlags);
                        break;

                      // handles: *, *::name, *::*, *::[expr]
                      case Token.MUL:
                        decompiler.addName("*");
                        pn = propertyName(pn, "*", memberTypeFlags);
                        break;

                      // handles: '@attr', '@ns::attr', '@ns::*', '@ns::*',
                      //          '@::attr', '@::*', '@*', '@*::attr', '@*::*'
                      case Token.XMLATTR:
                        decompiler.addToken(Token.XMLATTR);
                        pn = attributeAccess(pn, memberTypeFlags);
                        break;

                      default:
                        reportError("msg.no.name.after.dot");
                    }
                }
                break;

              case Token.DOTQUERY:
                consumeToken();
                mustHaveXML();
                decompiler.addToken(Token.DOTQUERY);
                pn = nf.createDotQuery(pn, expr(false), ts.getLineno());
                mustMatchToken(Token.RP, "msg.no.paren");
                decompiler.addToken(Token.RP);
                break;

              case Token.LB:
                consumeToken();
                decompiler.addToken(Token.LB);
                pn = nf.createElementGet(pn, null, expr(false), 0);
                mustMatchToken(Token.RB, "msg.no.bracket.index");
                decompiler.addToken(Token.RB);
                break;

              case Token.LP:
                if (!allowCallSyntax) {
                    break tailLoop;
                }
                consumeToken();
                decompiler.addToken(Token.LP);
                pn = nf.createCallOrNew(Token.CALL, pn);
                /* Add the arguments to pn, if any are supplied. */
                argumentList(pn);
                break;

              default:
                break tailLoop;
            }
        }
        return pn;
    }

    /*
     * Xml attribute expression:
     *   '@attr', '@ns::attr', '@ns::*', '@ns::*', '@*', '@*::attr', '@*::*'
     */
    private Node attributeAccess(Node pn, int memberTypeFlags)
        throws IOException
    {
        memberTypeFlags |= Node.ATTRIBUTE_FLAG;
        int tt = nextToken();

        switch (tt) {
          // handles: @name, @ns::name, @ns::*, @ns::[expr]
          case Token.NAME:
            {
                String s = ts.getString();
                decompiler.addName(s);
                pn = propertyName(pn, s, memberTypeFlags);
            }
            break;

          // handles: @*, @*::name, @*::*, @*::[expr]
          case Token.MUL:
            decompiler.addName("*");
            pn = propertyName(pn, "*", memberTypeFlags);
            break;

          // handles @[expr]
          case Token.LB:
            decompiler.addToken(Token.LB);
            pn = nf.createElementGet(pn, null, expr(false), memberTypeFlags);
            mustMatchToken(Token.RB, "msg.no.bracket.index");
            decompiler.addToken(Token.RB);
            break;

          default:
            reportError("msg.no.name.after.xmlAttr");
            pn = nf.createPropertyGet(pn, null, "?", memberTypeFlags);
            break;
        }

        return pn;
    }

    /**
     * Check if :: follows name in which case it becomes qualified name
     */
    private Node propertyName(Node pn, String name, int memberTypeFlags)
        throws IOException, ParserException
    {
        String namespace = null;
        if (matchToken(Token.COLONCOLON)) {
            decompiler.addToken(Token.COLONCOLON);
            namespace = name;

            int tt = nextToken();
            switch (tt) {
              // handles name::name
              case Token.NAME:
                name = ts.getString();
                decompiler.addName(name);
                break;

              // handles name::*
              case Token.MUL:
                decompiler.addName("*");
                name = "*";
                break;

              // handles name::[expr]
              case Token.LB:
                decompiler.addToken(Token.LB);
                pn = nf.createElementGet(pn, namespace, expr(false),
                                         memberTypeFlags);
                mustMatchToken(Token.RB, "msg.no.bracket.index");
                decompiler.addToken(Token.RB);
                return pn;

              default:
                reportError("msg.no.name.after.coloncolon");
                name = "?";
            }
        }

        pn = nf.createPropertyGet(pn, namespace, name, memberTypeFlags);
        return pn;
    }

    private Node primaryExpr()
        throws IOException, ParserException
    {
        Node pn;

        int ttFlagged = nextFlaggedToken();
        int tt = ttFlagged & CLEAR_TI_MASK;

        switch(tt) {

          case Token.FUNCTION:
            return function(FunctionNode.FUNCTION_EXPRESSION);

          case Token.LB: {
            ObjArray elems = new ObjArray();
            int skipCount = 0;
            decompiler.addToken(Token.LB);
            boolean after_lb_or_comma = true;
            for (;;) {
                tt = peekToken();

                if (tt == Token.COMMA) {
                    consumeToken();
                    decompiler.addToken(Token.COMMA);
                    if (!after_lb_or_comma) {
                        after_lb_or_comma = true;
                    } else {
                        elems.add(null);
                        ++skipCount;
                    }
                } else if (tt == Token.RB) {
                    consumeToken();
                    decompiler.addToken(Token.RB);
                    break;
                } else {
                    if (!after_lb_or_comma) {
                        reportError("msg.no.bracket.arg");
                    }
                    elems.add(assignExpr(false));
                    after_lb_or_comma = false;
                }
            }
            return nf.createArrayLiteral(elems, skipCount);
          }

          case Token.LC: {
            ObjArray elems = new ObjArray();
            decompiler.addToken(Token.LC);
            if (!matchToken(Token.RC)) {

                boolean first = true;
            commaloop:
                do {
                    Object property;

                    if (!first)
                        decompiler.addToken(Token.COMMA);
                    else
                        first = false;

                    tt = peekToken();
                    switch(tt) {
                      case Token.NAME:
                      case Token.STRING:
                        consumeToken();
                        // map NAMEs to STRINGs in object literal context
                        // but tell the decompiler the proper type
                        String s = ts.getString();
                        if (tt == Token.NAME) {
                            decompiler.addName(s);
                        } else {
                            decompiler.addString(s);
                        }
                        property = ScriptRuntime.getIndexObject(s);
                        break;

                      case Token.NUMBER:
                        consumeToken();
                        double n = ts.getNumber();
                        decompiler.addNumber(n);
                        property = ScriptRuntime.getIndexObject(n);
                        break;

                      case Token.RC:
                        // trailing comma is OK.
                        break commaloop;
                    default:
                        reportError("msg.bad.prop");
                        break commaloop;
                    }
                    mustMatchToken(Token.COLON, "msg.no.colon.prop");

                    // OBJLIT is used as ':' in object literal for
                    // decompilation to solve spacing ambiguity.
                    decompiler.addToken(Token.OBJECTLIT);
                    elems.add(property);
                    elems.add(assignExpr(false));
                } while (matchToken(Token.COMMA));

                mustMatchToken(Token.RC, "msg.no.brace.prop");
            }
            decompiler.addToken(Token.RC);
            return nf.createObjectLiteral(elems);
          }

          case Token.LP:

            /* Brendan's IR-jsparse.c makes a new node tagged with
             * TOK_LP here... I'm not sure I understand why.  Isn't
             * the grouping already implicit in the structure of the
             * parse tree?  also TOK_LP is already overloaded (I
             * think) in the C IR as 'function call.'  */
            decompiler.addToken(Token.LP);
            pn = expr(false);
            decompiler.addToken(Token.RP);
            mustMatchToken(Token.RP, "msg.no.paren");
            return pn;

          case Token.XMLATTR:
            mustHaveXML();
            decompiler.addToken(Token.XMLATTR);
            pn = attributeAccess(null, 0);
            return pn;

          case Token.NAME: {
            String name = ts.getString();
            if ((ttFlagged & TI_CHECK_LABEL) != 0) {
                if (peekToken() == Token.COLON) {
                    // Do not consume colon, it is used as unwind indicator
                    // to return to statementHelper.
                    // XXX Better way?
                    return nf.createLabel(ts.getLineno());
                }
            }

            decompiler.addName(name);
            if (compilerEnv.isXmlAvailable()) {
                pn = propertyName(null, name, 0);
            } else {
                pn = nf.createName(name);
            }
            return pn;
          }

          case Token.NUMBER: {
            double n = ts.getNumber();
            decompiler.addNumber(n);
            return nf.createNumber(n);
          }

          case Token.STRING: {
            String s = ts.getString();
            decompiler.addString(s);
            return nf.createString(s);
          }

          case Token.DIV:
          case Token.ASSIGN_DIV: {
            // Got / or /= which should be treated as regexp in fact
            ts.readRegExp(tt);
            String flags = ts.regExpFlags;
            ts.regExpFlags = null;
            String re = ts.getString();
            decompiler.addRegexp(re, flags);
            int index = currentScriptOrFn.addRegexp(re, flags);
            return nf.createRegExp(index);
          }

          case Token.NULL:
          case Token.THIS:
          case Token.FALSE:
          case Token.TRUE:
            decompiler.addToken(tt);
            return nf.createLeaf(tt);

          case Token.RESERVED:
            reportError("msg.reserved.id");
            break;

          case Token.ERROR:
            /* the scanner or one of its subroutines reported the error. */
            break;

          case Token.EOF:
            reportError("msg.unexpected.eof");
            break;

          default:
            reportError("msg.syntax");
            break;
        }
        return null;    // should never reach here
    }

}