通过COM发送和接收阵列

Sending and receiving arrays over COM

本文关键字：阵列 COM 通过      更新时间：2023-10-16

通过COM接收和发送数组的正确方法是什么？到目前为止，我的尝试是：一个由替身组成的安全阵列封装在一个变体中。

//takes variant holding safearray of doubles
//returns a similar variant having multipled every element by 2
STDMETHODIMP MyComClass::safearraytimestwo(VARIANT in, VARIANT* out)
{
    CComSafeArray<double> sa_in;
    sa_in.Attach(*in.pparray);
    ULONG size = sa_in.GetCount();
    CComSafeArray<double> *out_sa = new CComSafeArray<double>(size);
    for (long i=0;i<size;i++)
        out_sa->SetAt(i,sa_in[i]*2);
    out = new CComVariant(out_sa);
    return S_OK;
}

问题：-当前编译在循环操作上失败：error C2679: binary '=' : no operator found which takes a right-hand operand of type 'ATL::_ATL_AutomationType<DOUBLE>::_typewrapper' (or there is no acceptable conversion)编辑：使用SetAt()而不是operator[]解决-我应该在堆上声明out_sa吗？当out被解除分配时，它会被解除分配吗（我只能假设客户端会这样做？）

如有任何帮助，我们将不胜感激！

编辑2:这里有一个部分实现，它只尝试返回一个安全数组。

STDMETHODIMP CSpatialNet::array3(VARIANT in, VARIANT* out)
{
    CComSafeArray<double> out_sa;
    out_sa.Create(2);
    out_sa.SetAt(0,1.2);
    out_sa.SetAt(1,3.4);
    *out = CComVariant(out_sa);
    out_sa.Detach();
    return S_OK;
}

这也失败了；lisp报告

(vl-load-com)
(setq n (vlax-create-object "sdnacomwrapper.SpatialNet"))
(setq v (vlax-make-variant 1.0))
(vlax-invoke-method n 'array3 v 'newvar)
; error: ActiveX Server returned an error: The parameter is incorrect

用一系列变体替换CComSafeArray<double>会产生相同的错误。

实现了这一点-我的代码是这样的（编辑：尽管显然不是没有错误-请参阅Dietrich的答案）：

STDMETHODIMP MyComClass::arraytimestwo(VARIANT in, VARIANT* out)
{
    CComSafeArray<double> sa_in;
    sa_in.Attach(in.parray);
    ULONG size = sa_in.GetCount();
    CComSafeArray<double> out_sa;
    out_sa.Create(size);
    for (long i=0;i<size;i++)
        out_sa.SetAt(i,sa_in.GetAt(i)*2);
    CComVariant(out_sa).Detach(out);
    return S_OK;
}

在Lisp。。。

(vl-load-com)
(setq n (vlax-create-object "mycomdll.MyComClass"))
(setq sa (vlax-make-safearray vlax-vbDouble '(0 . 1)))
(vlax-safearray-fill sa '(1 2))
(vlax-safearray->list sa)
(vlax-invoke-method n 'arraytimestwo sa 'newvar)
(vlax-safearray->list newvar)

最初尝试的特别错误：

  • 需要使用Detach方法为out赋值
  • 需要连接到in.parray而不是*in.pparray（不是一回事）

采用VARIANT参数的COM方法负责检查参数、捕获异常，并且它不会真正破坏[in]数组，因此在C++端更准确的实现是：

STDMETHODIMP Foo(VARIANT in, VARIANT* out)
{
    _ATLTRY
    {
        ATLENSURE_THROW(in.vt == (VT_ARRAY | VT_R8), E_INVALIDARG);
        ATLENSURE_THROW(out, E_POINTER);
        VariantInit(out);
        CComSafeArray<DOUBLE>& sa_in =
            reinterpret_cast<CComSafeArray<DOUBLE>&>(in.parray);
        ULONG size = sa_in.GetCount();
        CComSafeArray<DOUBLE> out_sa;
        ATLENSURE_SUCCEEDED(out_sa.Create(size));
        for(ULONG nIndex = 0; nIndex < size; nIndex++)
            out_sa.SetAt(nIndex, sa_in.GetAt(nIndex) * 2);
        // NOTE: Constructor copies data so it's accurate just inefficient
        ATLVERIFY(SUCCEEDED(CComVariant(out_sa).Detach(out)));
    }
    _ATLCATCH(Exception)
    {
        return Exception;
    }
    return S_OK;
}

Sideshow Bob和Roman R.的解决方案使用

ComVariant(out_sa).Detach(out);

这有一个严重的缺点。SAFEARRAY out_sa被传递给CComVariant's构造函数，该构造函数将复制SAFEARRAY。为了避免复制，最好使用

::VariantInit(out);
out->vt = (VT_ARRAY | VT_R8);
out->parray = out_sa.Detach();

正如Roman所指出的，您还应该从检查in是否真的是VT_ARRAY | VT_R8类型开始。Bob的解决方案有一个严重的错误：in.parray附加到sa_in，但没有分离，因此析构函数将销毁in.parray。但是根据COM的规则，函数arraytimestwo(VARIANT in,...不允许修改参数in。COM充满陷阱。因此，我认为最好通过引用的方式传递参数in。

我给出了一个（希望如此！）改进的解决方案和测试功能：

STDMETHODIMP arraytimestwo(const VARIANT &in, VARIANT* out)
{
  try
  {
    if (in.vt != (VT_ARRAY | VT_R8)) return E_INVALIDARG;
    CComSafeArray<double> sa_out;
    variant_t wrapCopyIn(in);
    sa_out.Attach(wrapCopyIn.parray);
    if (sa_out.GetDimensions() > 1) return E_INVALIDARG;
    for (long i = sa_out.GetLowerBound(0); i <= sa_out.GetUpperBound(0); i++)
       sa_out[i] *= 2;
    //Don't forget
    sa_out.Detach();
    *out = wrapCopyIn.Detach();
  }
  catch (const CAtlException& e)
  {
    // Exception object implicitly converted to HRESULT,
    // and returned as an error code to the caller
    return e;
  }
  return S_OK;
}
void TestArraytimestwo()
{
  CComSafeArray<double> vec(5, 1);
  for (int i = vec.GetLowerBound(); i <= vec.GetUpperBound(); i++) vec[i] = i * 1.1;
  variant_t in, out;
  in.vt = (VT_ARRAY | VT_R8);
  in.parray = vec.Detach();
  if (!SUCCEEDED(arraytimestwo(in, &out)))
  {
   std::cout << "Something went wrong!" << "n";
   return;
  }
  CComSafeArray<double> sa_out;
  sa_out.Attach(out.parray);
  vec.Attach(in.parray);
  for (int i = vec.GetLowerBound(); i <= vec.GetUpperBound(); i++)
     std::cout << vec[i] << "  " << sa_out[i] << std::endl;
  //Not necessary, but I do it out of habit
  vec.Detach();
  sa_out.Detach();
}

备注：Bob原来的功能应该是这样的（跳过try…catch）

STDMETHODIMP arraytimestwoBob(const VARIANT &in, VARIANT* out)
{
  CComSafeArray<double> sa_in;
  sa_in.Attach(in.parray);
  CComSafeArray<double> out_sa(sa_in.GetCount(), sa_in.GetLowerBound());
  for (long i = sa_in.GetLowerBound(); i <= sa_in.GetUpperBound(); i++) out_sa[i] = 2 * sa_in[i];
  sa_in.Detach();//Detach, this function doesn't own in 
  ::VariantInit(out);
  out->vt = (VT_ARRAY | VT_R8);
  out->parray = out_sa.Detach();
  return S_OK;
}
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