如何遍历 SAFEARRAY **

2022-01-14 00:00:00 com c++ safearray

如何遍历 C++ 安全数组指针并访问其元素.

how to iterate through C++ safearray pointer to pointer and access its elements.

我尝试复制 Lim Bio Liong 发布的解决方案http://social.msdn.microsoft.com/Forums/en-US/vcgeneral/thread/022dba14-9abf-4872-9f43-f4fc05bd2602但最奇怪的是 IDL 方法签名竟然是

I tried to replicate the solution posted by Lim Bio Liong http://social.msdn.microsoft.com/Forums/en-US/vcgeneral/thread/022dba14-9abf-4872-9f43-f4fc05bd2602 but the strangest thing is that the IDL method signature comes out to be 

HRESULT __stdcall GetTestStructArray([out] SAFEARRAY ** test_struct_array);

而不是

HRESULT __stdcall GetTestStructArray([out] SAFEARRAY(TestStruct)* test_struct_array);

有什么想法吗?

提前致谢

推荐答案

Safearrays 是使用 SafeArrayCreate 或 SafeArrayCreateVector 创建的，但是当您询问迭代 SAFEARRAY 时，让我们假设您已经有其他函数返回的 SAFEARRAY .一种方法是使用 SafeArrayGetElement API，如果您有多维 SAFEARRAY，这会特别方便，因为它允许 IMO 更轻松地指定索引.

Safearrays are created with SafeArrayCreate or SafeArrayCreateVector, but as you ask about iterating over a SAFEARRAY, let's say you already have a SAFEARRAY returned by some other function. One way is to use SafeArrayGetElement API which is especially convenient if you have multidimensional SAFEARRAYs, as it allows, IMO, a bit easier specifying of the indices.

但是，对于向量(一维 SAFEARRAY)，直接访问数据并迭代值会更快.这是一个例子:

However, for vectors (unidimensional SAFEARRAY) it is faster to access data directly and iterate over the values. Here's an example:

假设它是 long 的 SAFEARRAY，即.VT_I4

Let's say it's a SAFEARRAY of longs, ie. VT_I4

// get them from somewhere. (I will assume that this is done 
// in a way that you are now responsible to free the memory)
SAFEARRAY* saValues = ... 
LONG* pVals;
HRESULT hr = SafeArrayAccessData(saValues, (void**)&pVals); // direct access to SA memory
if (SUCCEEDED(hr))
{
  long lowerBound, upperBound;  // get array bounds
  SafeArrayGetLBound(saValues, 1 , &lowerBound);
  SafeArrayGetUBound(saValues, 1, &upperBound);

  long cnt_elements = upperBound - lowerBound + 1; 
  for (int i = 0; i < cnt_elements; ++i)  // iterate through returned values
  {                              
    LONG lVal = pVals[i];   
    std::cout << "element " << i << ": value = " << lVal << std::endl;
  }       
  SafeArrayUnaccessData(saValues);
}
SafeArrayDestroy(saValues);

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