parser.java

Javassist是一个开源的分析、编辑和创建Java字节码的类库。是由东京技术学院的数学和计算机科学系的 Shigeru Chiba 所创建的。它已加入了开放源代码JBoss 应用服务器项目,通过使

    /* synchronized.statement :
     *     SYNCHRONIZED "(" expression ")" block.statement
     */
    private Stmnt parseSynchronized(SymbolTable tbl) throws CompileError {
        int t = lex.get();	// SYNCHRONIZED
        if (lex.get() != '(')
            throw new SyntaxError(lex);

        ASTree expr = parseExpression(tbl);
        if (lex.get() != ')')
            throw new SyntaxError(lex);

        Stmnt body = parseBlock(tbl);
        return new Stmnt(t, expr, body);
    }

    /* try.statement
     * : TRY block.statement
     *   [ CATCH "(" class.type Identifier ")" block.statement ]*
     *   [ FINALLY block.statement ]*
     */
    private Stmnt parseTry(SymbolTable tbl) throws CompileError {
        lex.get();      // TRY
        Stmnt block = parseBlock(tbl);
        ASTList catchList = null;
        while (lex.lookAhead() == CATCH) {
            lex.get();  // CATCH
            if (lex.get() != '(')
                throw new SyntaxError(lex);

            SymbolTable tbl2 = new SymbolTable(tbl);
            Declarator d = parseFormalParam(tbl2);
            if (d.getArrayDim() > 0 || d.getType() != CLASS)
                throw new SyntaxError(lex);

            if (lex.get() != ')')
                throw new SyntaxError(lex);

            Stmnt b = parseBlock(tbl2);
            catchList = ASTList.append(catchList, new Pair(d, b));
        }

        Stmnt finallyBlock = null;
        if (lex.lookAhead() == FINALLY) {
            lex.get();  // FINALLY
            finallyBlock = parseBlock(tbl);
        }

        return Stmnt.make(TRY, block, catchList, finallyBlock);
    }

    /* return.statement : RETURN [ expression ] ";"
     */
    private Stmnt parseReturn(SymbolTable tbl) throws CompileError {
        int t = lex.get();      // RETURN
        Stmnt s = new Stmnt(t);
        if (lex.lookAhead() != ';')
            s.setLeft(parseExpression(tbl));

        if (lex.get() != ';')
            throw new CompileError("; is missing", lex);

        return s;
    }

    /* throw.statement : THROW expression ";"
     */
    private Stmnt parseThrow(SymbolTable tbl) throws CompileError {
        int t = lex.get();      // THROW
        ASTree expr = parseExpression(tbl);
        if (lex.get() != ';')
            throw new CompileError("; is missing", lex);

        return new Stmnt(t, expr);
    }

    /* break.statement : BREAK [ Identifier ] ";"
     */
    private Stmnt parseBreak(SymbolTable tbl)
        throws CompileError
    {
        return parseContinue(tbl);
    }

    /* continue.statement : CONTINUE [ Identifier ] ";"
     */
    private Stmnt parseContinue(SymbolTable tbl)
        throws CompileError
    {
        int t = lex.get();      // CONTINUE
        Stmnt s = new Stmnt(t);
        int t2 = lex.get();
        if (t2 == Identifier) {
            s.setLeft(new Symbol(lex.getString()));
            t2 = lex.get();
        }

        if (t2 != ';')
            throw new CompileError("; is missing", lex);

        return s;
    }

    /* declaration.or.expression
     *      : [ FINAL ] built-in-type array.dimension declarators
     *      | [ FINAL ] class.type array.dimension declarators
     *      | expression ';'
     *      | expr.list ';'             if exprList is true
     *
     * Note: FINAL is currently ignored.  This must be fixed
     * in future.
     */
    private Stmnt parseDeclarationOrExpression(SymbolTable tbl,
                                               boolean exprList)
        throws CompileError
    {
        int t = lex.lookAhead();
        while (t == FINAL) {
            lex.get();
            t = lex.lookAhead();
        }

        if (isBuiltinType(t)) {
            t = lex.get();
            int dim = parseArrayDimension();
            return parseDeclarators(tbl, new Declarator(t, dim));
        }
        else if (t == Identifier) {
            int i = nextIsClassType(0);
            if (i >= 0)
                if (lex.lookAhead(i) == Identifier) {
                    ASTList name = parseClassType(tbl);
                    int dim = parseArrayDimension();
                    return parseDeclarators(tbl, new Declarator(name, dim));
                }
        }

        Stmnt expr;
        if (exprList)
            expr = parseExprList(tbl);
        else
            expr = new Stmnt(EXPR, parseExpression(tbl));

        if (lex.get() != ';')
            throw new CompileError("; is missing", lex);

        return expr;
    }

    /* expr.list : ( expression ',')* expression
     */
    private Stmnt parseExprList(SymbolTable tbl) throws CompileError {
        Stmnt expr = null;
        for (;;) {
            Stmnt e = new Stmnt(EXPR, parseExpression(tbl));
            expr = (Stmnt)ASTList.concat(expr, new Stmnt(BLOCK, e));
            if (lex.lookAhead() == ',')
                lex.get();
            else
                return expr;
        }
    }

    /* declarators : declarator [ ',' declarator ]* ';'
     */
    private Stmnt parseDeclarators(SymbolTable tbl, Declarator d)
        throws CompileError
    {
        Stmnt decl = null;
        for (;;) {
            decl = (Stmnt)ASTList.concat(decl,
                                new Stmnt(DECL, parseDeclarator(tbl, d)));
            int t = lex.get();
            if (t == ';')
                return decl;
            else if (t != ',')
                throw new CompileError("; is missing", lex);
        }
    }

    /* declarator : Identifier array.dimension [ '=' initializer ]
     */
    private Declarator parseDeclarator(SymbolTable tbl, Declarator d)
        throws CompileError
    {
        if (lex.get() != Identifier || d.getType() == VOID)
            throw new SyntaxError(lex);

        String name = lex.getString();
        Symbol symbol = new Symbol(name);
        int dim = parseArrayDimension();
        ASTree init = null;
        if (lex.lookAhead() == '=') {
            lex.get();
            init = parseInitializer(tbl);
        }

        Declarator decl = d.make(symbol, dim, init);
        tbl.append(name, decl);
        return decl;
    }

    /* initializer : expression | array.initializer
     */
    private ASTree parseInitializer(SymbolTable tbl) throws CompileError {
        if (lex.lookAhead() == '{')
            return parseArrayInitializer(tbl);
        else
            return parseExpression(tbl);
    }

    /* array.initializer :
     *  '{' (( array.initializer | expression ) ',')* '}'
     */
    private ArrayInit parseArrayInitializer(SymbolTable tbl)
        throws CompileError
    {
        lex.get();      // '{'
        ASTree expr = parseExpression(tbl);
        ArrayInit init = new ArrayInit(expr);
        while (lex.lookAhead() == ',') {
            lex.get();
            expr = parseExpression(tbl);
            ASTList.append(init, expr);
        }

        if (lex.get() != '}')
            throw new SyntaxError(lex);

        return init;
    }

    /* par.expression : '(' expression ')'
     */
    private ASTree parseParExpression(SymbolTable tbl) throws CompileError {
        if (lex.get() != '(')
            throw new SyntaxError(lex);

        ASTree expr = parseExpression(tbl);
        if (lex.get() != ')')
            throw new SyntaxError(lex);

        return expr;
    }

    /* expression : conditional.expr
     *            | conditional.expr assign.op expression (right-to-left)
     */
    public ASTree parseExpression(SymbolTable tbl) throws CompileError {
        ASTree left = parseConditionalExpr(tbl);
        if (!isAssignOp(lex.lookAhead()))
            return left;

        int t = lex.get();
        ASTree right = parseExpression(tbl);
        return AssignExpr.makeAssign(t, left, right);
    }

    private static boolean isAssignOp(int t) {
        return t == '=' || t == MOD_E || t == AND_E
                || t == MUL_E || t == PLUS_E || t == MINUS_E || t == DIV_E
                || t == EXOR_E || t == OR_E || t == LSHIFT_E
                || t == RSHIFT_E || t == ARSHIFT_E;
    }

    /* conditional.expr                 (right-to-left)
     *     : logical.or.expr [ '?' expression ':' conditional.expr ]
     */
    private ASTree parseConditionalExpr(SymbolTable tbl) throws CompileError {
        ASTree cond = parseBinaryExpr(tbl);
        if (lex.lookAhead() == '?') {
            lex.get();
            ASTree thenExpr = parseExpression(tbl);
            if (lex.get() != ':')
                throw new CompileError(": is missing", lex);

            ASTree elseExpr = parseExpression(tbl);
            return new CondExpr(cond, thenExpr, elseExpr);
        }
        else
            return cond;
    }

    /* logical.or.expr          10 (operator precedence)
     * : logical.and.expr
     * | logical.or.expr OROR logical.and.expr          left-to-right
     *
     * logical.and.expr         9
     * : inclusive.or.expr
     * | logical.and.expr ANDAND inclusive.or.expr
     *
     * inclusive.or.expr        8
     * : exclusive.or.expr
     * | inclusive.or.expr "|" exclusive.or.expr
     *
     * exclusive.or.expr        7
     *  : and.expr
     * | exclusive.or.expr "^" and.expr
     *
     * and.expr                 6
     * : equality.expr
     * | and.expr "&" equality.expr
     *
     * equality.expr            5
     * : relational.expr
     * | equality.expr (EQ | NEQ) relational.expr
     *
     * relational.expr          4
     * : shift.expr
     * | relational.expr (LE | GE | "<" | ">") shift.expr
     * | relational.expr INSTANCEOF class.type ("[" "]")*
     *
     * shift.expr               3
     * : additive.expr
     * | shift.expr (LSHIFT | RSHIFT | ARSHIFT) additive.expr
     *
     * additive.expr            2
     * : multiply.expr
     * | additive.expr ("+" | "-") multiply.expr
     *
     * multiply.expr            1
     * : unary.expr
     * | multiply.expr ("*" | "/" | "%") unary.expr
     */
    private ASTree parseBinaryExpr(SymbolTable tbl) throws CompileError {
        ASTree expr = parseUnaryExpr(tbl);
        for (;;) {
            int t = lex.lookAhead();
            int p = getOpPrecedence(t);
            if (p == 0)
                return expr;
            else
                expr = binaryExpr2(tbl, expr, p);
        }
    }

    private ASTree parseInstanceOf(SymbolTable tbl, ASTree expr)
        throws CompileError
    {
        int t = lex.lookAhead();
        if (isBuiltinType(t)) {
            lex.get();  // primitive type
            int dim = parseArrayDimension();
            return new InstanceOfExpr(t, dim, expr);
        }
        else {
            ASTList name = parseClassType(tbl);
            int dim = parseArrayDimension();
            return new InstanceOfExpr(name, dim, expr);
        }
    }

    private ASTree binaryExpr2(SymbolTable tbl, ASTree expr, int prec)
        throws CompileError
    {
        int t = lex.get();
        if (t == INSTANCEOF)
            return parseInstanceOf(tbl, expr);

        ASTree expr2 = parseUnaryExpr(tbl);
        for (;;) {
            int t2 = lex.lookAhead();
            int p2 = getOpPrecedence(t2);
            if (p2 != 0 && prec > p2)
                expr2 = binaryExpr2(tbl, expr2, p2);
            else
                return BinExpr.makeBin(t, expr, expr2);
        }
    }

    // !"#$%&'(    )*+,-./0    12345678    9:;<=>?
    private static final int[] binaryOpPrecedence
        =  { 0, 0, 0, 0, 1, 6, 0, 0,
             0, 1, 2, 0, 2, 0, 1, 0,
             0, 0, 0, 0, 0, 0, 0, 0,
             0, 0, 0, 4, 0, 4, 0 };

    private int getOpPrecedence(int c) {
        if ('!' <= c && c <= '?')
            return binaryOpPrecedence[c - '!'];
        else if (c == '^')
            return 7;
        else if (c == '|')
            return 8;
        else if (c == ANDAND)
            return 9;
        else if (c == OROR)
            return 10;
        else if (c == EQ || c == NEQ)
            return 5;
        else if (c == LE || c == GE || c == INSTANCEOF)
            return 4;
        else if (c == LSHIFT || c == RSHIFT || c == ARSHIFT)
            return 3;
        else
            return 0;   // not a binary operator
    }

    /* unary.expr : "++"|"--" unary.expr
                  | "+"|"-" unary.expr
                  | "!"|"~" unary.expr
                  | cast.expr
                  | postfix.expr

       unary.expr.not.plus.minus is a unary expression starting without
       "+", "-", "++", or "--".
     */
    private ASTree parseUnaryExpr(SymbolTable tbl) throws CompileError {
        int t;
        switch (lex.lookAhead()) {
        case '+' :
        case '-' :
        case PLUSPLUS :
        case MINUSMINUS :
        case '!' :
        case '~' :
            t = lex.get();
            if (t == '-') {
                int t2 = lex.lookAhead();
                switch (t2) {
                case LongConstant :
                case IntConstant :
                case CharConstant :
                    lex.get();
                    return new IntConst(-lex.getLong(), t2);
                case DoubleConstant :
                case FloatConstant :
                    lex.get();
                    return new DoubleConst(-lex.getDouble(), t2);
                default :
                    break;
                }
            }

            return Expr.make(t, parseUnaryExpr(tbl));
        case '(' :
            return parseCast(tbl);
        default :
            return parsePostfix(tbl);
        }
    }

    /* cast.expr : "(" builtin.type ("[" "]")* ")" unary.expr
                 | "(" class.type ("[" "]")* ")" unary.expr2

       unary.expr2 is a unary.expr begining with "(", NULL, StringL,
       Identifier, THIS, SUPER, or NEW.