jvstcodegen.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

            else {
                a.accept(this);
                types[i] = exprType;
                dims[i] = arrayDim;
                cnames[i] = className;
                ++i;
            }

            args = args.tail();
        }
    }

    /*
    public void atMethodArgs(ASTList args, int[] types, int[] dims,
                                String[] cnames) throws CompileError {
        if (!isParamListName(args)) {
            super.atMethodArgs(args, types, dims, cnames);
            return;
        }

        CtClass[] params = paramTypeList;
        if (params == null)
            return;

        int n = params.length;
        int regno = indexOfParam1();
        for (int i = 0; i < n; ++i) {
            CtClass p = params[i];
            regno += bytecode.addLoad(regno, p);
            setType(p);
            types[i] = exprType;
            dims[i] = arrayDim;
            cnames[i] = className;
        }
    }
    */

    /* called by Javac#recordSpecialProceed().
     */
    void compileInvokeSpecial(ASTree target, String classname,
                              String methodname, String descriptor,
                              ASTList args)
        throws CompileError
    {
        target.accept(this);
        int nargs = getMethodArgsLength(args);
        atMethodArgs(args, new int[nargs], new int[nargs],
                     new String[nargs]);
        bytecode.addInvokespecial(classname, methodname, descriptor);
        setReturnType(descriptor, false, false);
        addNullIfVoid();
    }

    /*
     * Makes it valid to write "return <expr>;" for a void method.
     */
    protected void atReturnStmnt(Stmnt st) throws CompileError {
        ASTree result = st.getLeft();
        if (result != null && returnType == CtClass.voidType) {
            compileExpr(result);
            if (is2word(exprType, arrayDim))
                bytecode.addOpcode(POP2);
            else if (exprType != VOID)
                bytecode.addOpcode(POP);

            result = null;
        }

        atReturnStmnt2(result);
    }

    /**
     * Makes a cast to the return type ($r) available.
     * It also enables $_.
     *
     * <p>If the return type is void, ($r) does nothing.
     * The type of $_ is java.lang.Object.
     *
     * @param resultName        null if $_ is not used.
     * @return          -1 or the variable index assigned to $_.
     */
    public int recordReturnType(CtClass type, String castName,
                 String resultName, SymbolTable tbl) throws CompileError
    {
        returnType = type;
        returnCastName = castName;
        returnVarName = resultName;
        if (resultName == null)
            return -1;
        else {
            int varNo = getMaxLocals();
            int locals = varNo + recordVar(type, resultName, varNo, tbl);
            setMaxLocals(locals);
            return varNo;
        }
    }

    /**
     * Makes $type available.
     */
    public void recordType(CtClass t) {
        dollarType = t;
    }

    /**
     * Makes method parameters $0, $1, ..., $args, $$, and $class available.
     * $0 is equivalent to THIS if the method is not static.  Otherwise,
     * if the method is static, then $0 is not available.
     */
    public int recordParams(CtClass[] params, boolean isStatic,
                             String prefix, String paramVarName,
                             String paramsName, SymbolTable tbl)
        throws CompileError
    {
        return recordParams(params, isStatic, prefix, paramVarName,
                            paramsName, !isStatic, 0, getThisName(), tbl);
    }

    /**
     * Makes method parameters $0, $1, ..., $args, $$, and $class available.
     * $0 is available only if use0 is true.  It might not be equivalent
     * to THIS.
     *
     * @param params    the parameter types (the types of $1, $2, ..)
     * @param prefix    it must be "$" (the first letter of $0, $1, ...)
     * @param paramVarName      it must be "$args"
     * @param paramsName        it must be "$$"
     * @param use0      true if $0 is used.
     * @param paramBase the register number of $0 (use0 is true)
     *                          or $1 (otherwise).
     * @param target    the class of $0.  If use0 is false, target
     *                  can be null.  The value of "target" is also used
     *                  as the name of the type represented by $class.
     * @param isStatic  true if the method in which the compiled bytecode
     *                  is embedded is static.
     */
    public int recordParams(CtClass[] params, boolean isStatic,
                            String prefix, String paramVarName,
                            String paramsName, boolean use0,
                            int paramBase, String target,
                            SymbolTable tbl)
        throws CompileError
    {
        int varNo;

        paramTypeList = params;
        paramArrayName = paramVarName;
        paramListName = paramsName;
        paramVarBase = paramBase;
        useParam0 = use0;

        if (target != null)
            param0Type = MemberResolver.jvmToJavaName(target);

        inStaticMethod = isStatic;
        varNo = paramBase;
        if (use0) {
            String varName = prefix + "0";
            Declarator decl
                = new Declarator(CLASS, MemberResolver.javaToJvmName(target),
                                 0, varNo++, new Symbol(varName));
            tbl.append(varName, decl);
        }

        for (int i = 0; i < params.length; ++i)
            varNo += recordVar(params[i], prefix + (i + 1), varNo, tbl);

        if (getMaxLocals() < varNo)
            setMaxLocals(varNo);

        return varNo;
    }

    /**
     * Makes the given variable name available.
     *
     * @param type      variable type
     * @param varName   variable name
     */
    public int recordVariable(CtClass type, String varName, SymbolTable tbl)
        throws CompileError
    {
        if (varName == null)
            return -1;
        else {
            int varNo = getMaxLocals();
            int locals = varNo + recordVar(type, varName, varNo, tbl);
            setMaxLocals(locals);
            return varNo;
        }
    }

    private int recordVar(CtClass cc, String varName, int varNo,
                          SymbolTable tbl) throws CompileError
    {
        if (cc == CtClass.voidType) {
            exprType = CLASS;
            arrayDim = 0;
            className = jvmJavaLangObject;
        }
        else
            setType(cc);

        Declarator decl
            = new Declarator(exprType, className, arrayDim,
                             varNo, new Symbol(varName));
        tbl.append(varName, decl);
        return is2word(exprType, arrayDim) ? 2 : 1;
    }

    /**
     * Makes the given variable name available.
     *
     * @param typeDesc  the type descriptor of the variable
     * @param varName   variable name
     * @param varNo     an index into the local variable array
     */
    public void recordVariable(String typeDesc, String varName, int varNo,
                               SymbolTable tbl) throws CompileError
    {
        char c;
        int dim = 0;
        while ((c = typeDesc.charAt(dim)) == '[')
            ++dim;

        int type = MemberResolver.descToType(c);
        String cname = null;
        if (type == CLASS) {
            if (dim == 0)
                cname = typeDesc.substring(1, typeDesc.length() - 1);
            else
                cname = typeDesc.substring(dim + 1, typeDesc.length() - 1);
        }

        Declarator decl
            = new Declarator(type, cname, dim, varNo, new Symbol(varName));
        tbl.append(varName, decl);
    }

    /* compileParameterList() returns the stack size used
     * by the produced code.
     *
     * This method correctly computes the max_stack value.
     *
     * @param regno     the index of the local variable in which
     *                  the first argument is received.
     *                  (0: static method, 1: regular method.)
     */
    public static int compileParameterList(Bytecode code,
                                CtClass[] params, int regno) {
        if (params == null) {
            code.addIconst(0);                          // iconst_0
            code.addAnewarray(javaLangObject);          // anewarray Object
            return 1;
        }
        else {
            CtClass[] args = new CtClass[1];
            int n = params.length;
            code.addIconst(n);                          // iconst_<n>
            code.addAnewarray(javaLangObject);          // anewarray Object
            for (int i = 0; i < n; ++i) {
                code.addOpcode(Bytecode.DUP);           // dup
                code.addIconst(i);                      // iconst_<i>
                if (params[i].isPrimitive()) {
                    CtPrimitiveType pt = (CtPrimitiveType)params[i];
                    String wrapper = pt.getWrapperName();
                    code.addNew(wrapper);               // new <wrapper>
                    code.addOpcode(Bytecode.DUP);       // dup
                    int s = code.addLoad(regno, pt);    // ?load <regno>
                    regno += s;
                    args[0] = pt;
                    code.addInvokespecial(wrapper, "<init>",
                                Descriptor.ofMethod(CtClass.voidType, args));
                                                        // invokespecial
                }
                else {
                    code.addAload(regno);               // aload <regno>
                    ++regno;
                }

                code.addOpcode(Bytecode.AASTORE);       // aastore
            }

            return 8;
        }
    }

    protected void compileUnwrapValue(CtClass type, Bytecode code)
        throws CompileError
    {
        if (type == CtClass.voidType) {
            addNullIfVoid();
            return;
        }

        if (exprType == VOID)
            throw new CompileError("invalid type for " + returnCastName);

        if (type instanceof CtPrimitiveType) {
            CtPrimitiveType pt = (CtPrimitiveType)type;
            // pt is not voidType.
            String wrapper = pt.getWrapperName();
            code.addCheckcast(wrapper);
            code.addInvokevirtual(wrapper, pt.getGetMethodName(),
                                  pt.getGetMethodDescriptor());
            setType(type);
        }
        else {
            code.addCheckcast(type);
            setType(type);
        }
    }

    /* Sets exprType, arrayDim, and className;
     * If type is void, then this method does nothing.
     */
    public void setType(CtClass type) throws CompileError {
        setType(type, 0);
    }

    private void setType(CtClass type, int dim) throws CompileError {
        if (type.isPrimitive()) {
            CtPrimitiveType pt = (CtPrimitiveType)type;
            exprType = MemberResolver.descToType(pt.getDescriptor());
            arrayDim = dim;
            className = null;
        }
        else if (type.isArray())
            try {
                setType(type.getComponentType(), dim + 1);
            }
            catch (NotFoundException e) {
                throw new CompileError("undefined type: " + type.getName());
            }
        else {
            exprType = CLASS;
            arrayDim = dim;
            className = MemberResolver.javaToJvmName(type.getName());
        }
    }

    /* Performs implicit coercion from exprType to type.
     */
    public void doNumCast(CtClass type) throws CompileError {
        if (arrayDim == 0 && !isRefType(exprType))
            if (type instanceof CtPrimitiveType) {
                CtPrimitiveType pt = (CtPrimitiveType)type;
                atNumCastExpr(exprType,
                              MemberResolver.descToType(pt.getDescriptor()));
            }
            else
                throw new CompileError("type mismatch");
    }
}