javac.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.CtClass;
import javassist.CtPrimitiveType;
import javassist.CtMember;
import javassist.CtField;
import javassist.CtBehavior;
import javassist.CtMethod;
import javassist.CtConstructor;
import javassist.CannotCompileException;
import javassist.Modifier;
import javassist.bytecode.Bytecode;
import javassist.bytecode.CodeAttribute;
import javassist.bytecode.LocalVariableAttribute;
import javassist.bytecode.Opcode;
import javassist.NotFoundException;

import javassist.compiler.ast.*;

public class Javac {
    JvstCodeGen gen;
    SymbolTable stable;
    private Bytecode bytecode;

    public static final String param0Name = "$0";
    public static final String resultVarName = "$_";
    public static final String proceedName = "$proceed";

    /**
     * Constructs a compiler.
     *
     * @param thisClass         the class that a compiled method/field
     *                          belongs to.
     */
    public Javac(CtClass thisClass) {
        this(new Bytecode(thisClass.getClassFile2().getConstPool(), 0, 0),
             thisClass);
    }

    /**
     * Constructs a compiler.
     * The produced bytecode is stored in the <code>Bytecode</code> object
     * specified by <code>b</code>.
     *
     * @param thisClass         the class that a compiled method/field
     *                          belongs to.
     */
    public Javac(Bytecode b, CtClass thisClass) {
        gen = new JvstCodeGen(b, thisClass, thisClass.getClassPool());
        stable = new SymbolTable();
        bytecode = b;
    }

    /**
     * Returns the produced bytecode.
     */
    public Bytecode getBytecode() { return bytecode; }

    /**
     * Compiles a method, constructor, or field declaration
     * to a class.
     * A field declaration can declare only one field.
     *
     * <p>In a method or constructor body, $0, $1, ... and $_
     * are not available.
     *
     * @return          a <code>CtMethod</code>, <code>CtConstructor</code>,
     *                  or <code>CtField</code> object.
     * @see #recordProceed(String,String)
     */
    public CtMember compile(String src) throws CompileError {
        Parser p = new Parser(new Lex(src));
        ASTList mem = p.parseMember1(stable);
        try {
            if (mem instanceof FieldDecl)
                return compileField((FieldDecl)mem);
            else
                return compileMethod(p, (MethodDecl)mem);
        }
        catch (CannotCompileException e) {
            throw new CompileError(e.getMessage());
        }
    }

    public static class CtFieldWithInit extends CtField {
        private ASTree init;

        CtFieldWithInit(CtClass type, String name, CtClass declaring)
            throws CannotCompileException
        {
            super(type, name, declaring);
            init = null;
        }

        protected void setInit(ASTree i) { init = i; }

        protected ASTree getInitAST() {
            return init;
        }
    }

    private CtField compileField(FieldDecl fd)
        throws CompileError, CannotCompileException
    {
        CtFieldWithInit f;
        Declarator d = fd.getDeclarator();
        f = new CtFieldWithInit(gen.resolver.lookupClass(d),
                                d.getVariable().get(), gen.getThisClass());
        f.setModifiers(MemberResolver.getModifiers(fd.getModifiers()));
        if (fd.getInit() != null)
            f.setInit(fd.getInit());

        return f;
    }

    private CtMember compileMethod(Parser p, MethodDecl md)
        throws CompileError
    {
        int mod = MemberResolver.getModifiers(md.getModifiers());
        CtClass[] plist = gen.makeParamList(md);
        CtClass[] tlist = gen.makeThrowsList(md);
        recordParams(plist, Modifier.isStatic(mod));
        md = p.parseMethod2(stable, md);
        try {
            if (md.isConstructor()) {
                CtConstructor cons = new CtConstructor(plist,
                                                   gen.getThisClass());
                cons.setModifiers(mod);
                md.accept(gen);
                cons.getMethodInfo().setCodeAttribute(
                                        bytecode.toCodeAttribute());
                cons.setExceptionTypes(tlist);
                return cons;
            }
            else {
                Declarator r = md.getReturn();
                CtClass rtype = gen.resolver.lookupClass(r);
                recordReturnType(rtype, false);
                CtMethod method = new CtMethod(rtype, r.getVariable().get(),
                                           plist, gen.getThisClass());
                method.setModifiers(mod);
                gen.setThisMethod(method);
                md.accept(gen);
                if (md.getBody() != null)
                    method.getMethodInfo().setCodeAttribute(
                                        bytecode.toCodeAttribute());
                else
                    method.setModifiers(mod | Modifier.ABSTRACT);

                method.setExceptionTypes(tlist);
                return method;
            }
        }
        catch (NotFoundException e) {
            throw new CompileError(e.toString());
        }
    }

    /**
     * Compiles a method (or constructor) body.
     *
     * @src	a single statement or a block.
     *          If null, this method produces a body returning zero or null.
     */
    public Bytecode compileBody(CtBehavior method, String src)
        throws CompileError
    {
        try {
            int mod = method.getModifiers();
            recordParams(method.getParameterTypes(), Modifier.isStatic(mod));

            CtClass rtype;
            if (method instanceof CtMethod) {
                gen.setThisMethod((CtMethod)method);
                rtype = ((CtMethod)method).getReturnType();
            }
            else
                rtype = CtClass.voidType;

            recordReturnType(rtype, false);
            boolean isVoid = rtype == CtClass.voidType;

            if (src == null)
                makeDefaultBody(bytecode, rtype);
            else {
                Parser p = new Parser(new Lex(src));
                SymbolTable stb = new SymbolTable(stable);
                Stmnt s = p.parseStatement(stb);
                if (p.hasMore())
                    throw new CompileError(
                        "the method/constructor body must be surrounded by {}");

                boolean callSuper = false;
                if (method instanceof CtConstructor)
                    callSuper = !((CtConstructor)method).isClassInitializer();

                gen.atMethodBody(s, callSuper, isVoid);
            }

            return bytecode;
        }
        catch (NotFoundException e) {
            throw new CompileError(e.toString());
        }
    }

    private static void makeDefaultBody(Bytecode b, CtClass type) {
        int op;
        int value;
        if (type instanceof CtPrimitiveType) {
            CtPrimitiveType pt = (CtPrimitiveType)type;
            op = pt.getReturnOp();
            if (op == Opcode.DRETURN)
                value = Opcode.DCONST_0;
            else if (op == Opcode.FRETURN)
                value = Opcode.FCONST_0;
            else if (op == Opcode.LRETURN)
                value = Opcode.LCONST_0;
            else if (op == Opcode.RETURN)
                value = Opcode.NOP;
            else
                value = Opcode.ICONST_0;
        }
        else {
            op = Opcode.ARETURN;
            value = Opcode.ACONST_NULL;
        }

        if (value != Opcode.NOP)
            b.addOpcode(value);

        b.addOpcode(op);
    }

    /**
     * Records local variables available at the specified program counter.
     * If the LocalVariableAttribute is not available, this method does not
     * record any local variable.  It only returns false.
     *
     * @param pc    program counter (&gt;= 0)
     * @return false if the CodeAttribute does not include a
     *              LocalVariableAttribute.
     */
    public boolean recordLocalVariables(CodeAttribute ca, int pc)
        throws CompileError
    {
        LocalVariableAttribute va
            = (LocalVariableAttribute)
              ca.getAttribute(LocalVariableAttribute.tag);
        if (va == null)
            return false;

        int n = va.tableLength();
        for (int i = 0; i < n; ++i) {
            int start = va.startPc(i);
            int len = va.codeLength(i);
            if (start <= pc && pc < start + len)
                gen.recordVariable(va.descriptor(i), va.variableName(i),
                                   va.index(i), stable);
        }

        return true;
    }

    /**
     * Records parameter names if the LocalVariableAttribute is available.
     * It returns false unless the LocalVariableAttribute is available.
     *
     * @param numOfLocalVars    the number of local variables used
     *                          for storing the parameters.
     * @return false if the CodeAttribute does not include a
     *              LocalVariableAttribute.
     */
    public boolean recordParamNames(CodeAttribute ca, int numOfLocalVars)
        throws CompileError
    {
        LocalVariableAttribute va
            = (LocalVariableAttribute)
              ca.getAttribute(LocalVariableAttribute.tag);
        if (va == null)
            return false;

        int n = va.tableLength();
        for (int i = 0; i < n; ++i) {
            int index = va.index(i);