C++ 如何遍历 SAFEARRAY **
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How to iterate through SAFEARRAY **
提问by TrustyCoder
how to iterate through C++ safearray pointer to pointer and access its elements.
如何遍历指向指针的 C++ 安全数组指针并访问其元素。
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-f4fc05bd2602but the strangest thing is that the IDL method signature comes out to be
我试图复制 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方法签名出来是
HRESULT __stdcall GetTestStructArray([out] SAFEARRAY ** test_struct_array);
instead of
代替
HRESULT __stdcall GetTestStructArray([out] SAFEARRAY(TestStruct)* test_struct_array);
Any ideas?
有任何想法吗？
thanks in advance
提前致谢
回答by Zdeslav Vojkovic
Safearrays are created with SafeArrayCreateor 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 SafeArrayGetElementAPI which is especially convenient if you have multidimensional SAFEARRAYs, as it allows, IMO, a bit easier specifying of the indices.
Safearrays 是用SafeArrayCreateor创建的SafeArrayCreateVector，但是当您询问迭代 SAFEARRAY 时，假设您已经有一个由其他函数返回的 SAFEARRAY。一种方法是使用SafeArrayGetElementAPI，如果您有多维 SAFEARRAY，它会特别方便，因为它允许 IMO 更轻松地指定索引。
However, for vectors (unidimensional SAFEARRAY) it is faster to access data directly and iterate over the values. Here's an example:
但是，对于向量（一维 SAFEARRAY），直接访问数据并迭代这些值会更快。下面是一个例子：
Let's say it's a SAFEARRAY of longs, ie. VT_I4
假设它是longs的 SAFEARRAY ，即。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);
回答by Roman R.
MSDN SafeArrayGetElement functiongives you a code snippet on using SafeArrayGetElementto obtain individual object to array.
MSDN SafeArrayGetElement 函数为您提供了一个SafeArrayGetElement用于获取单个对象到数组的代码片段。
SAFEARRAYstructureand SafeArray*functions explain the available API.
SAFEARRAY结构和SafeArray*函数解释了可用的 API。
In ATL/MFC project you would want to use wrapper classes e.g. CComSafeArrayto make things simpler and easier. See Simplifying SAFEARRAY programming with CComSafeArrayon this.
在 ATL/MFC 项目中，您可能希望使用包装类，例如CComSafeArray使事情更简单更容易。有关此内容，请参阅使用 CComSafeArray 简化 SAFEARRAY 编程。
