membercodegen.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

                fi = addFieldrefInfo(f, finfo);
            else
                fi = 0;
        }
        else
            fi = atFieldRead(f, is_static);

        int fType = exprType;
        int fDim = arrayDim;
        String cname = className;

        atAssignCore(expr, op, right, fType, fDim, cname);

        boolean is2w = is2word(fType, fDim);
        if (doDup) {
            int dup_code;
            if (is_static)
                dup_code = (is2w ? DUP2 : DUP);
            else
                dup_code = (is2w ? DUP2_X1 : DUP_X1);

            bytecode.addOpcode(dup_code);
        }

        atFieldAssignCore(f, is_static, fi, is2w);

        exprType = fType;
        arrayDim = fDim;
        className = cname;
    }

    /* If fi == 0, the field must be a private field in an enclosing class.
     */
    private void atFieldAssignCore(CtField f, boolean is_static, int fi,
                                   boolean is2byte) throws CompileError {
        if (fi != 0) {
            if (is_static) {
               bytecode.add(PUTSTATIC);
               bytecode.growStack(is2byte ? -2 : -1);
            }
            else {
                bytecode.add(PUTFIELD);
                bytecode.growStack(is2byte ? -3 : -2);
            }
        
            bytecode.addIndex(fi);
        }
        else {
            CtClass declClass = f.getDeclaringClass();
            AccessorMaker maker = declClass.getAccessorMaker();
            // make should be non null.
            FieldInfo finfo = f.getFieldInfo2();
            MethodInfo minfo = maker.getFieldSetter(finfo, is_static);
            bytecode.addInvokestatic(declClass, minfo.getName(),
                                     minfo.getDescriptor());
        }
    }

    /* overwritten in JvstCodeGen.
     */
    public void atMember(Member mem) throws CompileError {
        atFieldRead(mem);
    }

    protected void atFieldRead(ASTree expr) throws CompileError
    {
        CtField f = fieldAccess(expr, true);
        if (f == null) {
            atArrayLength(expr);
            return;
        }

        boolean is_static = resultStatic;
        ASTree cexpr = TypeChecker.getConstantFieldValue(f);
        if (cexpr == null)
            atFieldRead(f, is_static);
        else {
            cexpr.accept(this);
            setFieldType(f.getFieldInfo2());
        }
    }

    private void atArrayLength(ASTree expr) throws CompileError {
        if (arrayDim == 0)
            throw new CompileError(".length applied to a non array");

        bytecode.addOpcode(ARRAYLENGTH);
        exprType = INT;
        arrayDim = 0;
    }

    /**
     * Generates bytecode for reading a field value.
     * It returns a fieldref_info index or zero if the field is a private
     * one declared in an enclosing class. 
     */
    private int atFieldRead(CtField f, boolean isStatic) throws CompileError {
        FieldInfo finfo = f.getFieldInfo2();
        boolean is2byte = setFieldType(finfo);
        AccessorMaker maker = isAccessibleField(f, finfo);
        if (maker != null) {
            MethodInfo minfo = maker.getFieldGetter(finfo, isStatic);
            bytecode.addInvokestatic(f.getDeclaringClass(), minfo.getName(),
                                     minfo.getDescriptor());
            return 0;
        }
        else {
            int fi = addFieldrefInfo(f, finfo);
            if (isStatic) {
                bytecode.add(GETSTATIC);
                bytecode.growStack(is2byte ? 2 : 1);
            }
            else {
                bytecode.add(GETFIELD);
                bytecode.growStack(is2byte ? 1 : 0);
            }

            bytecode.addIndex(fi);
            return fi;
        }
    }

    /**
     * Returns null if the field is accessible.  Otherwise, it throws
     * an exception or it returns AccessorMaker if the field is a private
     * one declared in an enclosing class.
     */
    private AccessorMaker isAccessibleField(CtField f, FieldInfo finfo)
        throws CompileError
    {
        if (AccessFlag.isPrivate(finfo.getAccessFlags())
            && f.getDeclaringClass() != thisClass) {
            CtClass declClass = f.getDeclaringClass(); 
            if (isEnclosing(declClass, thisClass)) {
                AccessorMaker maker = declClass.getAccessorMaker();
                if (maker != null)
                    return maker;
                else
                    throw new CompileError("fatal error.  bug?");
            }
            else
                throw new CompileError("Field " + f.getName() + " in "
                                       + declClass.getName() + " is private.");
        }

        return null;    // accessible field
    }

    /**
     * Sets exprType, arrayDim, and className.
     *
     * @return true if the field type is long or double. 
     */
    private boolean setFieldType(FieldInfo finfo) throws CompileError {
        String type = finfo.getDescriptor();

        int i = 0;
        int dim = 0;
        char c = type.charAt(i);
        while (c == '[') {
            ++dim;
            c = type.charAt(++i);
        }

        arrayDim = dim;
        exprType = MemberResolver.descToType(c);

        if (c == 'L')
            className = type.substring(i + 1, type.indexOf(';', i + 1));
        else
            className = null;

        boolean is2byte = (c == 'J' || c == 'D');
        return is2byte;
    }

    private int addFieldrefInfo(CtField f, FieldInfo finfo) {
        ConstPool cp = bytecode.getConstPool();
        String cname = f.getDeclaringClass().getName();
        int ci = cp.addClassInfo(cname);
        String name = finfo.getName();
        String type = finfo.getDescriptor();
        return cp.addFieldrefInfo(ci, name, type);
    }

    protected void atFieldPlusPlus(int token, boolean isPost,
                                   ASTree oprand, Expr expr, boolean doDup)
        throws CompileError
    {
        CtField f = fieldAccess(oprand, false);
        boolean is_static = resultStatic;
        if (!is_static)
            bytecode.addOpcode(DUP);

        int fi = atFieldRead(f, is_static);
        int t = exprType;
        boolean is2w = is2word(t, arrayDim);

        int dup_code;
        if (is_static)
            dup_code = (is2w ? DUP2 : DUP);
        else
            dup_code = (is2w ? DUP2_X1 : DUP_X1);

        atPlusPlusCore(dup_code, doDup, token, isPost, expr);
        atFieldAssignCore(f, is_static, fi, is2w);
    }

    /* This method also returns a value in resultStatic.
     *
     * @param acceptLength      true if array length is acceptable
     */
    protected CtField fieldAccess(ASTree expr, boolean acceptLength)
            throws CompileError
    {
        if (expr instanceof Member) {
            String name = ((Member)expr).get();
            CtField f = null;
            try {
                f = thisClass.getField(name);
            }
            catch (NotFoundException e) {
                // EXPR might be part of a static member access?
                throw new NoFieldException(name, expr);
            }

            boolean is_static = Modifier.isStatic(f.getModifiers());
            if (!is_static)
                if (inStaticMethod)
                    throw new CompileError(
                                "not available in a static method: " + name);
                else
                    bytecode.addAload(0);       // this

            resultStatic = is_static;
            return f;
        }
        else if (expr instanceof Expr) {
            Expr e = (Expr)expr;
            int op = e.getOperator();
            if (op == MEMBER) {
                /* static member by # (extension by Javassist)
                 * For example, if int.class is parsed, the resulting tree
                 * is (# "java.lang.Integer" "TYPE"). 
                 */
                CtField f = resolver.lookupField(((Symbol)e.oprand1()).get(),
                                         (Symbol)e.oprand2());
                resultStatic = true;
                return f;
            }
            else if (op == '.') {
                CtField f = null;
                try {
                    e.oprand1().accept(this);
                    /* Don't call lookupFieldByJvmName2().
                     * The left operand of . is not a class name but
                     * a normal expression.
                     */
                    if (exprType == CLASS && arrayDim == 0)
                        f = resolver.lookupFieldByJvmName(className,
                                                    (Symbol)e.oprand2());
                    else if (acceptLength && arrayDim > 0
                             && ((Symbol)e.oprand2()).get().equals("length"))
                        return null;    // expr is an array length.
                    else
                        badLvalue();

                    boolean is_static = Modifier.isStatic(f.getModifiers());
                    if (is_static)
                        bytecode.addOpcode(POP);

                    resultStatic = is_static;
                    return f;
                }
                catch (NoFieldException nfe) {
                    if (nfe.getExpr() != e.oprand1())
                        throw nfe;

                    /* EXPR should be a static field.
                     * If EXPR might be part of a qualified class name,
                     * lookupFieldByJvmName2() throws NoFieldException.
                     */
                    Symbol fname = (Symbol)e.oprand2();
                    String cname = nfe.getField();
                    f = resolver.lookupFieldByJvmName2(cname, fname, expr);
                    resolver.recordPackage(cname);
                    resultStatic = true;
                    return f;
                }
            }
            else
                badLvalue();
        }
        else
            badLvalue();

        resultStatic = false;
        return null;    // never reach
    }

    private static void badLvalue() throws CompileError {
        throw new CompileError("bad l-value");
    }

    public CtClass[] makeParamList(MethodDecl md) throws CompileError {
        CtClass[] params;
        ASTList plist = md.getParams();
        if (plist == null)
            params = new CtClass[0];
        else {
            int i = 0;
            params = new CtClass[plist.length()];
            while (plist != null) {
                params[i++] = resolver.lookupClass((Declarator)plist.head());
                plist = plist.tail();
            }
        }

        return params;
    }

    public CtClass[] makeThrowsList(MethodDecl md) throws CompileError {
        CtClass[] clist;
        ASTList list = md.getThrows();
        if (list == null)
            return null;
        else {
            int i = 0;
            clist = new CtClass[list.length()];
            while (list != null) {
                clist[i++] = resolver.lookupClassByName((ASTList)list.head());
                list = list.tail();
            }

            return clist;
        }
    }

    /* Converts a class name into a JVM-internal representation.
     *
     * It may also expand a simple class name to java.lang.*.
     * For example, this converts Object into java/lang/Object.
     */
    protected String resolveClassName(ASTList name) throws CompileError {
        return resolver.resolveClassName(name);
    }

    /* Expands a simple class name to java.lang.*.
     * For example, this converts Object into java/lang/Object.
     */
    protected String resolveClassName(String jvmName) throws CompileError {
        return resolver.resolveJvmClassName(jvmName);
    }
}