将SAFEARRAY从c++返回到c#
本文关键字：返回 c++ SAFEARRAY | 更新日期: 2023-09-27 17:59:20
我有一个c++方法，它创建、填充并返回SAFEARRAY:
SAFEARRAY* TestClass::GetResult(long& size)
{
return GetSafeArrayList(size);
}
How should I export that function in a DLL so that c# could take it
How should I write c# method signature?
我在c++中有这样的东西：
extern "C" __declspec(dllexport) void GetResult(SAFEARRAY*& data, long& size)
{
size = 0;
data = handle->GetResult(size);
}
这是正确的吗？
谢谢你的帮助！
编辑：
c#调用：
public static extern void GetResult(IntPtr handle, [MarshalAs(UnmanagedType.SafeArray, SafeArraySubType = VarEnum.VT_USERDEFINED)] TestStruct[] data, ref int size);
SAFEARRAY(int) C#->C++->C#的完整使用示例（因此数组用C#中的一些数据初始化，传递给C++，在那里修改并返回给C#）。
C++：
// For the various _t classes for handling BSTR and IUnknown
#include <comdef.h>
struct ManagedUDT
{
BSTR m_str01;
int m_int01;
~ManagedUDT()
{
::SysFreeString(m_str01);
m_str01 = NULL;
}
};
extern "C" __declspec(dllexport) void GetResult(SAFEARRAY*& data)
{
if (data != NULL)
{
// Begin print content of SAFEARRAY
VARTYPE vt;
HRESULT hr = SafeArrayGetVartype(data, &vt);
if (SUCCEEDED(hr))
{
// To make this code simple, we print only
// SAFEARRAY(VT_I4)
if (vt == VT_I4)
{
int *pVals;
hr = SafeArrayAccessData(data, (void**)&pVals); // direct access to SA memory
if (SUCCEEDED(hr))
{
long lowerBound, upperBound; // get array bounds
SafeArrayGetLBound(data, 1, &lowerBound);
SafeArrayGetUBound(data, 1, &upperBound);
long cnt_elements = upperBound - lowerBound + 1;
for (int i = 0; i < cnt_elements; i++) // iterate through returned values
{
int val = pVals[i];
printf("C++: %d'n", val);
}
SafeArrayUnaccessData(data);
}
else
{
// Error
}
}
}
else
{
// Error
}
// End print content of SAFEARRAY
// Delete the SAFEARRAY if already present
SafeArrayDestroy(data);
data = NULL;
}
{
// Creation of a new SAFEARRAY
SAFEARRAYBOUND bounds;
bounds.lLbound = 0;
bounds.cElements = 10;
data = SafeArrayCreate(VT_I4, 1, &bounds);
int *pVals;
HRESULT hr = SafeArrayAccessData(data, (void**)&pVals); // direct access to SA memory
if (SUCCEEDED(hr))
{
for (ULONG i = 0; i < bounds.cElements; i++)
{
pVals[i] = i + 100;
}
}
else
{
// Error
}
}
}
C#
[DllImport("NativeLibrary.dll", CallingConvention = CallingConvention.Cdecl)]
private static extern void GetResult([MarshalAs(UnmanagedType.SafeArray, SafeArraySubType = VarEnum.VT_I4)] ref int[] ar);
和
var data = new int[] { 1, 2, 3, 4, 5 };
GetResult(ref data);
if (data != null)
{
for (int i = 0; i < data.Length; i++)
{
Console.WriteLine("C#: {0}", data[i]);
}
}
else
{
Console.WriteLine("C#: data is null");
}
代码部分取自https://stackoverflow.com/a/12484259/613130和https://stackoverflow.com/a/3735438/613130
SAFEARRAY（VT_RECORD）
这是可行的。。。很难。。。但可行。请不要这样做。你再恨这个世界也不为过。我希望你不要这样做！
C++：
// For the _com_util
#include <comdef.h>
extern "C"
{
__declspec(dllexport) void GetResultSafeArray(SAFEARRAY *&psa)
{
// All the various hr results should be checked!
HRESULT hr;
// Begin sanity checks
if (psa == NULL)
{
// Error
}
VARTYPE pvt;
hr = ::SafeArrayGetVartype(psa, &pvt);
if (pvt != VT_RECORD)
{
// Error
}
UINT size;
size = ::SafeArrayGetElemsize(psa);
if (size != sizeof(ManagedUDT))
{
// Error
}
// From tests done, it seems SafeArrayGetRecordInfo does a AddRef
_com_ptr_t<_com_IIID<IRecordInfo, NULL> > prinfo;
// The_com_ptr_t<>::operator& is overloaded
hr = ::SafeArrayGetRecordInfo(psa, &prinfo);
// From tests done, it seems GetName returns a new instance of the
// BSTR
// It is ok to use _bstr_t.GetAddress() here, see its description
_bstr_t name1;
hr = prinfo->GetName(name1.GetAddress());
const _bstr_t name2 = _bstr_t(L"ManagedUDT");
if (name1 != name2)
{
// Error
}
// End sanity checks
long lowerBound, upperBound; // get array bounds
hr = ::SafeArrayGetLBound(psa, 1, &lowerBound);
hr = ::SafeArrayGetUBound(psa, 1, &upperBound);
long cnt_elements = upperBound - lowerBound + 1;
// Begin print
ManagedUDT *pVals;
hr = ::SafeArrayAccessData(psa, (void**)&pVals);
printf("C++:'n");
for (int i = 0; i < cnt_elements; ++i)
{
ManagedUDT *pVal = pVals + i;
// If you are using a recent VisualC++, you can
// #include <memory>, and then
//std::unique_ptr<char[]> pstr(_com_util::ConvertBSTRToString(pVal->m_str01));
// and you don't need the char *pstr line and the delete[]
// line
char *pstr = _com_util::ConvertBSTRToString(pVal->m_str01);
printf("%s, %d'n", pstr, pVal->m_int01);
delete[] pstr;
}
hr = ::SafeArrayUnaccessData(psa);
// End print
// Begin free
SAFEARRAYBOUND sab;
sab.lLbound = 0;
sab.cElements = 0;
// SafeArrayRedim will call IRecordInfo::RecordClear
hr = ::SafeArrayRedim(psa, &sab);
// End Free
// Begin create
int numElements = 10;
sab.cElements = numElements;
hr = ::SafeArrayRedim(psa, &sab);
hr = ::SafeArrayAccessData(psa, (void**)&pVals);
for (int i = 0; i < numElements; i++)
{
ManagedUDT *pVal = pVals + i;
char pstr[100];
sprintf(pstr, "Element #%d", i);
pVal->m_str01 = _com_util::ConvertStringToBSTR(pstr);
pVal->m_int01 = 100 + i;
}
hr = ::SafeArrayUnaccessData(psa);
// End create
}
__declspec(dllexport) void GetResultSafeArrayOut(SAFEARRAY *&psa, ITypeInfo *itypeinfo)
{
// All the various hr results should be checked!
HRESULT hr;
// Begin sanity checks
if (psa != NULL)
{
// Begin free
// SafeArrayDestroy will call IRecordInfo::RecordClear
// if necessary
hr = ::SafeArrayDestroy(psa);
// End Free
}
// Begin create
int numElements = 10;
SAFEARRAYBOUND sab;
sab.lLbound = 0;
sab.cElements = numElements;
// The_com_ptr_t<>::operator& is overloaded
_com_ptr_t<_com_IIID<IRecordInfo, NULL> > prinfo;
hr = ::GetRecordInfoFromTypeInfo(itypeinfo, &prinfo);
psa = ::SafeArrayCreateVectorEx(VT_RECORD, 0, numElements, prinfo);
ManagedUDT *pVals;
hr = ::SafeArrayAccessData(psa, (void**)&pVals);
for (int i = 0; i < numElements; i++)
{
ManagedUDT *pVal = pVals + i;
char pstr[100];
sprintf(pstr, "Element #%d", i);
pVal->m_str01 = _com_util::ConvertStringToBSTR(pstr);
pVal->m_int01 = 100 + i;
}
hr = ::SafeArrayUnaccessData(psa);
// End create
}
}
C#：
[ComVisible(true)]
[Guid("BBFE1092-A90C-4b6d-B279-CBA28B9EDDFA")]
[StructLayout(LayoutKind.Sequential)]
public struct ManagedUDT
{
[MarshalAs(UnmanagedType.BStr)]
public string m_str01;
public Int32 m_int01;
}
[DllImport("NativeLibrary.dll", CallingConvention = CallingConvention.Cdecl, CharSet = CharSet.Ansi)]
static extern void GetResultSafeArray([MarshalAs(UnmanagedType.SafeArray)] ref ManagedUDT[] array);
[DllImport("NativeLibrary.dll", CallingConvention = CallingConvention.Cdecl, CharSet = CharSet.Ansi)]
static extern void GetResultSafeArrayOut([MarshalAs(UnmanagedType.SafeArray)] out ManagedUDT[] array, IntPtr itypeinfo);
[DllImport("NativeLibrary.dll", CallingConvention = CallingConvention.Cdecl, CharSet = CharSet.Ansi, EntryPoint = "GetResultSafeArrayOut")]
static extern void GetResultSafeArrayRef([MarshalAs(UnmanagedType.SafeArray)] ref ManagedUDT[] array, IntPtr itypeinfo);
和
var arr = new[]
{
new ManagedUDT { m_str01 = "Foo", m_int01 = 1},
new ManagedUDT { m_str01 = "Bar", m_int01 = 2},
};
{
Console.WriteLine("C#:");
for (int i = 0; i < arr.Length; i++)
{
Console.WriteLine("{0}, {1}", arr[i].m_str01, arr[i].m_int01);
}
}
{
Console.WriteLine();
var arr2 = (ManagedUDT[])arr.Clone();
GetResultSafeArray(ref arr2);
Console.WriteLine();
Console.WriteLine("C#:");
for (int i = 0; i < arr2.Length; i++)
{
Console.WriteLine("{0}, {1}", arr2[i].m_str01, arr2[i].m_int01);
}
}
{
Console.WriteLine();
ManagedUDT[] arr2;
IntPtr itypeinfo = Marshal.GetITypeInfoForType(typeof(ManagedUDT));
GetResultSafeArrayOut(out arr2, itypeinfo);
Console.WriteLine();
Console.WriteLine("C#:");
for (int i = 0; i < arr2.Length; i++)
{
Console.WriteLine("{0}, {1}", arr2[i].m_str01, arr2[i].m_int01);
}
}
{
Console.WriteLine();
var arr2 = (ManagedUDT[])arr.Clone();
IntPtr itypeinfo = Marshal.GetITypeInfoForType(typeof(ManagedUDT));
GetResultSafeArrayRef(ref arr2, itypeinfo);
Console.WriteLine();
Console.WriteLine("C#:");
for (int i = 0; i < arr2.Length; i++)
{
Console.WriteLine("{0}, {1}", arr2[i].m_str01, arr2[i].m_int01);
}
}
对于GetResultSafeArray有一个很大的警告：您必须从C#传递至少一个空数组（如new ManagedUDT[0]）。这是因为要在C++中从无到有地创建SAFEARRAY(ManagedUDT)，您需要一个IRecordInfo对象。我不知道如何从C++中检索它。如果你已经有了SAFEARRAY(ManagedUDT)，那么很明显它已经设置了IRecordInfo，所以没有问题。在给定的示例中，在C++中，首先进行一些健全性检查，然后打印传递的数组，然后清空它，然后重新填充它。GetResultSafeArrayOut/GetResultSafeArrayRef"欺骗"：它们从C#接收一个ITypeInfo指针（在C#中使用Marshal.GetITypeInfoForType()很容易检索），C++可以从中检索IRecordInfo接口。
一些注意事项：
我写了Ansi字符集C++。通常我自己总是编写支持Unicode的C++（或直接的Unicode-C++，因为所有的Windows NT都支持Unicode），但我注意到我是个例外。。。因此，在代码的各个部分都有BSTR->Ansi->BSTR的转换。
我正在检索所有函数调用的
HRESULT。应该检查它们，并处理故障。C++/COM中最复杂的事情是知道什么时候释放一些东西。。。总的来说，总是免费/
Release()一切（无论是BSTR/IUnknown派生接口，…）除非出现错误，否则不支持此代码。把它看作是概念的证明。出于好奇，我已经为此浪费了好几个小时。你打破它，你就修复它。