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

/*
 * Javassist, a Java-bytecode translator toolkit.
 * Copyright (C) 1999-2006 Shigeru Chiba. All Rights Reserved.
 *
 * 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.  Alternatively, the contents of this file may be used under
 * the terms of the GNU Lesser General Public License Version 2.1 or later.
 *
 * 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.
 */

package javassist.compiler;

import javassist.compiler.ast.*;

public final class Parser implements TokenId {
    private Lex lex;

    public Parser(Lex lex) {
        this.lex = lex;
    }

    public boolean hasMore() { return lex.lookAhead() >= 0; }

    /* member.declaration
     * : method.declaration | field.declaration
     */
    public ASTList parseMember(SymbolTable tbl) throws CompileError {
        ASTList mem = parseMember1(tbl);
        if (mem instanceof MethodDecl)
            return parseMethod2(tbl, (MethodDecl)mem);
        else
            return mem;
    }

    /* A method body is not parsed.
     */
    public ASTList parseMember1(SymbolTable tbl) throws CompileError {
        ASTList mods = parseMemberMods();
        Declarator d;
        boolean isConstructor = false;
        if (lex.lookAhead() == Identifier && lex.lookAhead(1) == '(') {
            d = new Declarator(VOID, 0);
            isConstructor = true;
        }
        else
            d = parseFormalType(tbl);

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

        String name;
        if (isConstructor)
            name = MethodDecl.initName;
        else
            name = lex.getString();

        d.setVariable(new Symbol(name));
        if (isConstructor || lex.lookAhead() == '(')
            return parseMethod1(tbl, isConstructor, mods, d);
        else
            return parseField(tbl, mods, d);
    }

    /* field.declaration
     *  : member.modifiers
     *    formal.type Identifier
     *    [ "=" expression ] ";"
     */
    private FieldDecl parseField(SymbolTable tbl, ASTList mods,
                                Declarator d) throws CompileError
    {
        ASTree expr = null;
        if (lex.lookAhead() == '=') {
            lex.get();
            expr = parseExpression(tbl);
        }

        int c = lex.get();
        if (c == ';')
            return new FieldDecl(mods, new ASTList(d, new ASTList(expr)));
        else if (c == ',')
            throw new CompileError(
                "only one field can be declared in one declaration", lex);
        else
            throw new SyntaxError(lex);
    }

    /* method.declaration
     *  : member.modifiers
     *    [ formal.type ]
     *    Identifier "(" [ formal.parameter ( "," formal.parameter )* ] ")"
     *    array.dimension
     *    [ THROWS class.type ( "," class.type ) ]
     *    ( block.statement | ";" )
     *
     * Note that a method body is not parsed.
     */
    private MethodDecl parseMethod1(SymbolTable tbl, boolean isConstructor,
                                    ASTList mods, Declarator d)
        throws CompileError
    {
        if (lex.get() != '(')
            throw new SyntaxError(lex);

        ASTList parms = null;
        if (lex.lookAhead() != ')')
            while (true) {
                parms = ASTList.append(parms, parseFormalParam(tbl));
                int t = lex.lookAhead();
                if (t == ',')
                    lex.get();
                else if (t == ')')
                    break;
            }

        lex.get();      // ')'
        d.addArrayDim(parseArrayDimension());
        if (isConstructor && d.getArrayDim() > 0)
            throw new SyntaxError(lex);

        ASTList throwsList = null;
        if (lex.lookAhead() == THROWS) {
            lex.get();
            while (true) {
                throwsList = ASTList.append(throwsList, parseClassType(tbl));
                if (lex.lookAhead() == ',')
                    lex.get();
                else
                    break;
            }
        }

        return new MethodDecl(mods, new ASTList(d,
                                ASTList.make(parms, throwsList, null)));
    }

    /* Parses a method body.
     */
    public MethodDecl parseMethod2(SymbolTable tbl, MethodDecl md)
        throws CompileError
    {
        Stmnt body = null;
        if (lex.lookAhead() == ';')
            lex.get();
        else {
            body = parseBlock(tbl);
            if (body == null)
                body = new Stmnt(BLOCK);
        }

        md.sublist(4).setHead(body);
        return md;
    }

    /* member.modifiers
     *  : ( FINAL | SYNCHRONIZED | ABSTRACT
     *    | PUBLIC | PROTECTED | PRIVATE | STATIC
     *    | VOLATILE | TRANSIENT | STRICT )*
     */
    private ASTList parseMemberMods() {
        int t;
        ASTList list = null;
        while (true) {
            t = lex.lookAhead();
            if (t == ABSTRACT || t == FINAL || t == PUBLIC || t == PROTECTED
                || t == PRIVATE || t == SYNCHRONIZED || t == STATIC
                || t == VOLATILE || t == TRANSIENT || t == STRICT)
                list = new ASTList(new Keyword(lex.get()), list);
            else
                break;
        }

        return list;
    }

    /* formal.type : ( build-in-type | class.type ) array.dimension
     */
    private Declarator parseFormalType(SymbolTable tbl) throws CompileError {
        int t = lex.lookAhead();
        if (isBuiltinType(t) || t == VOID) {
            lex.get();  // primitive type
            int dim = parseArrayDimension();
            return new Declarator(t, dim);
        }
        else {
            ASTList name = parseClassType(tbl);
            int dim = parseArrayDimension();
            return new Declarator(name, dim);
        }
    }

    private static boolean isBuiltinType(int t) {
        return (t == BOOLEAN || t == BYTE || t == CHAR || t == SHORT
                || t == INT || t == LONG || t == FLOAT || t == DOUBLE);
    }

    /* formal.parameter : formal.type Identifier array.dimension
     */
    private Declarator parseFormalParam(SymbolTable tbl)
        throws CompileError
    {
        Declarator d = parseFormalType(tbl);
        if (lex.get() != Identifier)
            throw new SyntaxError(lex);

        String name = lex.getString();
        d.setVariable(new Symbol(name));
        d.addArrayDim(parseArrayDimension());
        tbl.append(name, d);
        return d;
    }

    /* statement : [ label ":" ]* labeled.statement
     *
     * labeled.statement
     *          : block.statement
     *          | if.statement
     *          | while.statement
     *          | do.statement
     *          | for.statement
     *          | switch.statement
     *          | try.statement
     *          | return.statement
     *          | thorw.statement
     *          | break.statement
     *          | continue.statement
     *          | declaration.or.expression
     *          | ";"
     *
     * This method may return null (empty statement).
     */
    public Stmnt parseStatement(SymbolTable tbl)
        throws CompileError
    {
        int t = lex.lookAhead();
        if (t == '{')
            return parseBlock(tbl);
        else if (t == ';') {
            lex.get();
            return new Stmnt(BLOCK);    // empty statement
        }
        else if (t == Identifier && lex.lookAhead(1) == ':') {
            lex.get();  // Identifier
            String label = lex.getString();
            lex.get();  // ':'
            return Stmnt.make(LABEL, new Symbol(label), parseStatement(tbl));
        }
        else if (t == IF)
            return parseIf(tbl);
        else if (t == WHILE)
            return parseWhile(tbl);
        else if (t == DO)
            return parseDo(tbl);
        else if (t == FOR)
            return parseFor(tbl);
        else if (t == TRY)
            return parseTry(tbl);
        else if (t == SWITCH)
            return parseSwitch(tbl);
        else if (t == SYNCHRONIZED)
            return parseSynchronized(tbl);
        else if (t == RETURN)
            return parseReturn(tbl);
        else if (t == THROW)
            return parseThrow(tbl);
        else if (t == BREAK)
            return parseBreak(tbl);
        else if (t == CONTINUE)
            return parseContinue(tbl);
        else
            return parseDeclarationOrExpression(tbl, false);
    }

    /* block.statement : "{" statement* "}"
     */
    private Stmnt parseBlock(SymbolTable tbl) throws CompileError {
        if (lex.get() != '{')
            throw new SyntaxError(lex);

        Stmnt body = null;
        SymbolTable tbl2 = new SymbolTable(tbl);
        while (lex.lookAhead() != '}') {
            Stmnt s = parseStatement(tbl2);
            if (s != null)
                body = (Stmnt)ASTList.concat(body, new Stmnt(BLOCK, s));
        }

        lex.get();      // '}'
        if (body == null)
            return new Stmnt(BLOCK);    // empty block
        else
            return body;
    }

    /* if.statement : IF "(" expression ")" statement
     *                [ ELSE statement ]
     */
    private Stmnt parseIf(SymbolTable tbl) throws CompileError {
        int t = lex.get();      // IF
        ASTree expr = parseParExpression(tbl);
        Stmnt thenp = parseStatement(tbl);
        Stmnt elsep;
        if (lex.lookAhead() == ELSE) {
            lex.get();
            elsep = parseStatement(tbl);
        }
        else
            elsep = null;

        return new Stmnt(t, expr, new ASTList(thenp, new ASTList(elsep)));
    }

    /* while.statement : WHILE "(" expression ")" statement
     */
    private Stmnt parseWhile(SymbolTable tbl)
        throws CompileError
    {
        int t = lex.get();      // WHILE
        ASTree expr = parseParExpression(tbl);
        Stmnt body = parseStatement(tbl);
        return new Stmnt(t, expr, body);
    }

    /* do.statement : DO statement WHILE "(" expression ")" ";"
     */
    private Stmnt parseDo(SymbolTable tbl) throws CompileError {
        int t = lex.get();      // DO
        Stmnt body = parseStatement(tbl);
        if (lex.get() != WHILE || lex.get() != '(')
            throw new SyntaxError(lex);

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

        return new Stmnt(t, expr, body);
    }

    /* for.statement : FOR "(" decl.or.expr expression ";" expression ")"
     *                 statement
     */
    private Stmnt parseFor(SymbolTable tbl) throws CompileError {
        Stmnt expr1, expr3;
        ASTree expr2;
        int t = lex.get();      // FOR

        SymbolTable tbl2 = new SymbolTable(tbl);

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

        if (lex.lookAhead() == ';') {
            lex.get();
            expr1 = null;
        }
        else
            expr1 = parseDeclarationOrExpression(tbl2, true);

        if (lex.lookAhead() == ';')
            expr2 = null;
        else
            expr2 = parseExpression(tbl2);

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

        if (lex.lookAhead() == ')')
            expr3 = null;
        else
            expr3 = parseExprList(tbl2);

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

        Stmnt body = parseStatement(tbl2);
        return new Stmnt(t, expr1, new ASTList(expr2,
                                               new ASTList(expr3, body)));
    }

    /* switch.statement : SWITCH "(" expression ")" "{" switch.block "}"
     *
     * swtich.block : ( switch.label statement* )*
     *
     * swtich.label : DEFAULT ":"
     *              | CASE const.expression ":"
     */
    private Stmnt parseSwitch(SymbolTable tbl) throws CompileError {
        int t = lex.get();	// SWITCH
        ASTree expr = parseParExpression(tbl);
        Stmnt body = parseSwitchBlock(tbl);
        return new Stmnt(t, expr, body);
    }

    private Stmnt parseSwitchBlock(SymbolTable tbl) throws CompileError {
        if (lex.get() != '{')
            throw new SyntaxError(lex);

        SymbolTable tbl2 = new SymbolTable(tbl);
        Stmnt s = parseStmntOrCase(tbl2);
        if (s == null)
            throw new CompileError("empty switch block", lex);

        int op = s.getOperator();
        if (op != CASE && op != DEFAULT)
            throw new CompileError("no case or default in a switch block",
                                   lex);

        Stmnt body = new Stmnt(BLOCK, s);
        while (lex.lookAhead() != '}') {
            Stmnt s2 = parseStmntOrCase(tbl2);
            if (s2 != null) {
                int op2 = s2.getOperator();
                if (op2 == CASE || op2 == DEFAULT) {
                    body = (Stmnt)ASTList.concat(body, new Stmnt(BLOCK, s2));
                    s = s2;
                }
                else
                    s = (Stmnt)ASTList.concat(s, new Stmnt(BLOCK, s2));
            }
        }

        lex.get();      // '}'
        return body;
    }

    private Stmnt parseStmntOrCase(SymbolTable tbl) throws CompileError {
        int t = lex.lookAhead();
        if (t != CASE && t != DEFAULT)
            return parseStatement(tbl);

        lex.get();
        Stmnt s;
        if (t == CASE)
            s = new Stmnt(t, parseExpression(tbl));
        else
            s = new Stmnt(DEFAULT);

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

        return s;
    }