parser.java

是一款用JAVA 编写的编译器 具有很强的编译功能

            int pos = S.pos();
            S.nextToken();
            odStack[top] = topOp == INSTANCEOF ? type() : term3();
            while (top > 0 && prec(topOp) >= prec(S.token())) {
                odStack[top-1] = makeOp(pos, topOp, odStack[top-1],
                                        odStack[top]);
                top--;
                topOp = opStack[top];
            }
        }
        assert top == 0;
        t = odStack[0];

        if (t.getTag() == JCTree.PLUS) {
            StringBuffer buf = foldStrings(t);
            if (buf != null) {
                t = toP(F.at(startPos).Literal(TypeTags.CLASS, buf.toString()));
            }
        }

        odStackSupply.elems = savedOd; // optimization
        opStackSupply.elems = savedOp; // optimization
        return t;
    }
//where
        /** Construct a binary or type test node.
         */
        private JCExpression makeOp(int pos,
                                    Token topOp,
                                    JCExpression od1,
                                    JCExpression od2)
        {
            if (topOp == INSTANCEOF) {
                return F.at(pos).TypeTest(od1, od2);
            } else {
                return F.at(pos).Binary(optag(topOp), od1, od2);
            }
        }
        /** If tree is a concatenation of string literals, replace it
         *  by a single literal representing the concatenated string.
         */
        protected StringBuffer foldStrings(JCTree tree) {
            List<String> buf = List.nil();
            while (true) {
                if (tree.getTag() == JCTree.LITERAL) {
                    JCLiteral lit = (JCLiteral) tree;
                    if (lit.typetag == TypeTags.CLASS) {
                        StringBuffer sbuf =
                            new StringBuffer((String)lit.value);
                        while (buf.nonEmpty()) {
                            sbuf.append(buf.head);
                            buf = buf.tail;
                        }
                        return sbuf;
                    }
                } else if (tree.getTag() == JCTree.PLUS) {
                    JCBinary op = (JCBinary)tree;
                    if (op.rhs.getTag() == JCTree.LITERAL) {
                        JCLiteral lit = (JCLiteral) op.rhs;
                        if (lit.typetag == TypeTags.CLASS) {
                            buf = buf.prepend((String) lit.value);
                            tree = op.lhs;
                            continue;
                        }
                    }
                }
                return null;
            }
        }

        /** optimization: To save allocating a new operand/operator stack
         *  for every binary operation, we use supplys.
         */
        ListBuffer<JCExpression[]> odStackSupply = new ListBuffer<JCExpression[]>();
        ListBuffer<Token[]> opStackSupply = new ListBuffer<Token[]>();

        private JCExpression[] newOdStack() {
            if (odStackSupply.elems == odStackSupply.last)
                odStackSupply.append(new JCExpression[infixPrecedenceLevels + 1]);
            JCExpression[] odStack = odStackSupply.elems.head;
            odStackSupply.elems = odStackSupply.elems.tail;
            return odStack;
        }

        private Token[] newOpStack() {
            if (opStackSupply.elems == opStackSupply.last)
                opStackSupply.append(new Token[infixPrecedenceLevels + 1]);
            Token[] opStack = opStackSupply.elems.head;
            opStackSupply.elems = opStackSupply.elems.tail;
            return opStack;
        }

    /** Expression3    = PrefixOp Expression3
     *                 | "(" Expr | TypeNoParams ")" Expression3
     *                 | Primary {Selector} {PostfixOp}
     *  Primary        = "(" Expression ")"
     *                 | Literal
     *                 | [TypeArguments] THIS [Arguments]
     *                 | [TypeArguments] SUPER SuperSuffix
     *                 | NEW [TypeArguments] Creator
     *                 | Ident { "." Ident }
     *                   [ "[" ( "]" BracketsOpt "." CLASS | Expression "]" )
     *                   | Arguments
     *                   | "." ( CLASS | THIS | [TypeArguments] SUPER Arguments | NEW [TypeArguments] InnerCreator )
     *                   ]
     *                 | BasicType BracketsOpt "." CLASS
     *  PrefixOp       = "++" | "--" | "!" | "~" | "+" | "-"
     *  PostfixOp      = "++" | "--"
     *  Type3          = Ident { "." Ident } [TypeArguments] {TypeSelector} BracketsOpt
     *                 | BasicType
     *  TypeNoParams3  = Ident { "." Ident } BracketsOpt
     *  Selector       = "." [TypeArguments] Ident [Arguments]
     *                 | "." THIS
     *                 | "." [TypeArguments] SUPER SuperSuffix
     *                 | "." NEW [TypeArguments] InnerCreator
     *                 | "[" Expression "]"
     *  TypeSelector   = "." Ident [TypeArguments]
     *  SuperSuffix    = Arguments | "." Ident [Arguments]
     */
    protected JCExpression term3() {
        int pos = S.pos();
        JCExpression t;
        List<JCExpression> typeArgs = typeArgumentsOpt(EXPR);
        switch (S.token()) {
        case QUES:
            if ((mode & TYPE) != 0 && (mode & (TYPEARG|NOPARAMS)) == TYPEARG) {
                mode = TYPE;
                return typeArgument();
            } else
                return illegal();
        case PLUSPLUS: case SUBSUB: case BANG: case TILDE: case PLUS: case SUB:
            if (typeArgs == null && (mode & EXPR) != 0) {
                Token token = S.token();
                S.nextToken();
                mode = EXPR;
                if (token == SUB &&
                    (S.token() == INTLITERAL || S.token() == LONGLITERAL) &&
                    S.radix() == 10) {
                    mode = EXPR;
                    t = literal(names.hyphen);
                } else {
                    t = term3();
                    return F.at(pos).Unary(unoptag(token), t);
                }
            } else return illegal();
            break;
        case LPAREN:
            if (typeArgs == null && (mode & EXPR) != 0) {
                S.nextToken();
                mode = EXPR | TYPE | NOPARAMS;
                t = term3();
                if ((mode & TYPE) != 0 && S.token() == LT) {
                    // Could be a cast to a parameterized type
                    int op = JCTree.LT;
                    int pos1 = S.pos();
                    S.nextToken();
                    mode &= (EXPR | TYPE);
                    mode |= TYPEARG;
                    JCExpression t1 = term3();
                    if ((mode & TYPE) != 0 &&
                        (S.token() == COMMA || S.token() == GT)) {
                        mode = TYPE;
                        ListBuffer<JCExpression> args = new ListBuffer<JCExpression>();
                        args.append(t1);
                        while (S.token() == COMMA) {
                            S.nextToken();
                            args.append(typeArgument());
                        }
                        accept(GT);
                        t = F.at(pos1).TypeApply(t, args.toList());
                        checkGenerics();
                        t = bracketsOpt(toP(t));
                    } else if ((mode & EXPR) != 0) {
                        mode = EXPR;
                        t = F.at(pos1).Binary(op, t, term2Rest(t1, TreeInfo.shiftPrec));
                        t = termRest(term1Rest(term2Rest(t, TreeInfo.orPrec)));
                    } else {
                        accept(GT);
                    }
                } else {
                    t = termRest(term1Rest(term2Rest(t, TreeInfo.orPrec)));
                }
                accept(RPAREN);
                lastmode = mode;
                mode = EXPR;
                if ((lastmode & EXPR) == 0) {
                    JCExpression t1 = term3();
                    return F.at(pos).TypeCast(t, t1);
                } else if ((lastmode & TYPE) != 0) {
                    switch (S.token()) {
                    /*case PLUSPLUS: case SUBSUB: */
                    case BANG: case TILDE:
                    case LPAREN: case THIS: case SUPER:
                    case INTLITERAL: case LONGLITERAL: case FLOATLITERAL:
                    case DOUBLELITERAL: case CHARLITERAL: case STRINGLITERAL:
                    case TRUE: case FALSE: case NULL:
                    case NEW: case IDENTIFIER: case ASSERT: case ENUM:
                    case BYTE: case SHORT: case CHAR: case INT:
                    case LONG: case FLOAT: case DOUBLE: case BOOLEAN: case VOID:
                        JCExpression t1 = term3();
                        return F.at(pos).TypeCast(t, t1);
                    }
                }
            } else return illegal();
            t = toP(F.at(pos).Parens(t));
            break;
        case THIS:
            if ((mode & EXPR) != 0) {
                mode = EXPR;
                t = to(F.at(pos).Ident(names._this));
                S.nextToken();
                if (typeArgs == null)
                    t = argumentsOpt(null, t);
                else
                    t = arguments(typeArgs, t);
                typeArgs = null;
            } else return illegal();
            break;
        case SUPER:
            if ((mode & EXPR) != 0) {
                mode = EXPR;
                t = to(superSuffix(typeArgs, F.at(pos).Ident(names._super)));
                typeArgs = null;
            } else return illegal();
            break;
        case INTLITERAL: case LONGLITERAL: case FLOATLITERAL: case DOUBLELITERAL:
        case CHARLITERAL: case STRINGLITERAL:
        case TRUE: case FALSE: case NULL:
            if (typeArgs == null && (mode & EXPR) != 0) {
                mode = EXPR;
                t = literal(names.empty);
            } else return illegal();
            break;
        case NEW:
            if (typeArgs != null) return illegal();
            if ((mode & EXPR) != 0) {
                mode = EXPR;
                S.nextToken();
                if (S.token() == LT) typeArgs = typeArguments();
                t = creator(pos, typeArgs);
                typeArgs = null;
            } else return illegal();
            break;
        case IDENTIFIER: case ASSERT: case ENUM:
            if (typeArgs != null) return illegal();
            t = toP(F.at(S.pos()).Ident(ident()));
            loop: while (true) {
                pos = S.pos();
                switch (S.token()) {
                case LBRACKET:
                    S.nextToken();
                    if (S.token() == RBRACKET) {
                        S.nextToken();
                        t = bracketsOpt(t);
                        t = toP(F.at(pos).TypeArray(t));
                        t = bracketsSuffix(t);
                    } else {
                        if ((mode & EXPR) != 0) {
                            mode = EXPR;
                            JCExpression t1 = term();
                            t = to(F.at(pos).Indexed(t, t1));
                        }
                        accept(RBRACKET);
                    }
                    break loop;
                case LPAREN:
                    if ((mode & EXPR) != 0) {
                        mode = EXPR;
                        t = arguments(typeArgs, t);
                        typeArgs = null;
                    }
                    break loop;
                case DOT:
                    S.nextToken();
                    typeArgs = typeArgumentsOpt(EXPR);
                    if ((mode & EXPR) != 0) {
                        switch (S.token()) {
                        case CLASS:
                            if (typeArgs != null) return illegal();
                            mode = EXPR;
                            t = to(F.at(pos).Select(t, names._class));
                            S.nextToken();
                            break loop;
                        case THIS:
                            if (typeArgs != null) return illegal();
                            mode = EXPR;
                            t = to(F.at(pos).Select(t, names._this));
                            S.nextToken();
                            break loop;
                        case SUPER:
                            mode = EXPR;
                            t = to(F.at(pos).Select(t, names._super));
                            t = superSuffix(typeArgs, t);
                            typeArgs = null;
                            break loop;
                        case NEW:
                            if (typeArgs != null) return illegal();
                            mode = EXPR;
                            int pos1 = S.pos();
                            S.nextToken();
                            if (S.token() == LT) typeArgs = typeArguments();
                            t = innerCreator(pos1, typeArgs, t);
                            typeArgs = null;
                            break loop;
                        }
                    }
                    // typeArgs saved for next loop iteration.
                    t = toP(F.at(pos).Select(t, ident()));
                    break;
                default:
                    break loop;
                }
            }
            if (typeArgs != null) illegal();
            t = typeArgumentsOpt(t);
            break;
        case BYTE: case SHORT: case CHAR: case INT: case LONG: case FLOAT:
        case DOUBLE: case BOOLEAN:
            if (typeArgs != null) illegal();
            t = bracketsSuffix(bracketsOpt(basicType()));
            break;
        case VOID:
            if (typeArgs != null) illegal();
            if ((mode & EXPR) != 0) {
                S.nextToken();
                if (S.token() == DOT) {
                    JCPrimitiveTypeTree ti = toP(F.at(pos).TypeIdent(TypeTags.VOID));
                    t = bracketsSuffix(ti);
                } else {
                    return illegal(pos);
                }
            } else {
                return illegal();
            }
            break;
        default:
            return illegal();
        }
        if (typeArgs != null) illegal();
        while (true) {
            int pos1 = S.pos();
            if (S.token() == LBRACKET) {
                S.nextToken();
                if ((mode & TYPE) != 0) {
                    int oldmode = mode;
                    mode = TYPE;
                    if (S.token() == RBRACKET) {
                        S.nextToken();
                        t = bracketsOpt(t);
                        t = toP(F.at(pos1).TypeArray(t));
                        return t;
                    }
                    mode = oldmode;
                }
                if ((mode & EXPR) != 0) {
                    mode = EXPR;
                    JCExpression t1 = term();
                    t = to(F.at(pos1).Indexed(t, t1));
                }
                accept(RBRACKET);
            } else if (S.token() == DOT) {
                S.nextToken();
                typeArgs = typeArgumentsOpt(EXPR);
                if (S.token() == SUPER && (mode & EXPR) != 0) {
                    mode = EXPR;
                    t = to(F.at(pos1).Select(t, names._super));
                    S.nextToken();