在纯C中使用DispCallFunc调用IStream::SetSize(0)的方法如下:
首先,需要引入相关的头文件和库文件:
#include <windows.h>
#include <objbase.h>
#include <stdio.h>
然后,定义相关的接口和函数指针:
typedef struct _IStreamVtbl {
HRESULT(STDMETHODCALLTYPE *QueryInterface)(IStream *This, REFIID riid, void **ppvObject);
ULONG(STDMETHODCALLTYPE *AddRef)(IStream *This);
ULONG(STDMETHODCALLTYPE *Release)(IStream *This);
HRESULT(STDMETHODCALLTYPE *Read)(IStream *This, void *pv, ULONG cb, ULONG *pcbRead);
HRESULT(STDMETHODCALLTYPE *Write)(IStream *This, const void *pv, ULONG cb, ULONG *pcbWritten);
HRESULT(STDMETHODCALLTYPE *Seek)(IStream *This, LARGE_INTEGER dlibMove, DWORD dwOrigin, ULARGE_INTEGER *plibNewPosition);
HRESULT(STDMETHODCALLTYPE *SetSize)(IStream *This, ULARGE_INTEGER libNewSize);
HRESULT(STDMETHODCALLTYPE *CopyTo)(IStream *This, IStream *pstm, ULARGE_INTEGER cb, ULARGE_INTEGER *pcbRead, ULARGE_INTEGER *pcbWritten);
HRESULT(STDMETHODCALLTYPE *Commit)(IStream *This, DWORD grfCommitFlags);
HRESULT(STDMETHODCALLTYPE *Revert)(IStream *This);
HRESULT(STDMETHODCALLTYPE *LockRegion)(IStream *This, ULARGE_INTEGER libOffset, ULARGE_INTEGER cb, DWORD dwLockType);
HRESULT(STDMETHODCALLTYPE *UnlockRegion)(IStream *This, ULARGE_INTEGER libOffset, ULARGE_INTEGER cb, DWORD dwLockType);
HRESULT(STDMETHODCALLTYPE *Stat)(IStream *This, STATSTG *pstatstg, DWORD grfStatFlag);
HRESULT(STDMETHODCALLTYPE *Clone)(IStream *This, IStream **ppstm);
} IStreamVtbl;
typedef struct _IStream {
IStreamVtbl *lpVtbl;
} IStream;
typedef HRESULT(STDMETHODCALLTYPE *DispCallFunc)(void *pvInstance, ULONG oVft, CC *cc, VARTYPE vtReturn, UINT cActuals, VARTYPE *prgvt, VARIANTARG **prgpvarg, VARIANT *pvargResult);
接下来,实现调用函数:
void CallIStreamSetSize()
{
HMODULE hOle32 = LoadLibraryA("ole32.dll");
if (hOle32 == NULL) {
printf("Failed to load ole32.dll\n");
return;
}
DispCallFunc pDispCallFunc = (DispCallFunc)GetProcAddress(hOle32, "DispCallFunc");
if (pDispCallFunc == NULL) {
printf("Failed to get address of DispCallFunc\n");
FreeLibrary(hOle32);
return;
}
IStream *pStream = NULL;
HRESULT hr = CoCreateInstance(&CLSID_NULL, NULL, CLSCTX_INPROC_SERVER, &IID_IStream, (void **)&pStream);
if (FAILED(hr)) {
printf("Failed to create IStream instance\n");
FreeLibrary(hOle32);
return;
}
IStreamVtbl *pStreamVtbl = pStream->lpVtbl;
ULONG oVft = (ULONG)((char *)&pStreamVtbl->SetSize - (char *)pStreamVtbl);
CC cc = CC_STDCALL;
VARTYPE vtReturn = VT_HRESULT;
UINT cActuals = 2;
VARTYPE rgvt[2] = { VT_UNKNOWN, VT_UI8 };
VARIANTARG pvarg[2] = { 0 };
pvarg[0].vt = VT_UNKNOWN;
pvarg[0].punkVal = NULL;
pvarg[1].vt = VT_UI8;
pvarg[1].ullVal = 0;
VARIANT vResult;
VariantInit(&vResult);
hr = pDispCallFunc(pStream, oVft, &cc, vtReturn, cActuals, rgvt, &pvarg, &vResult);
if (FAILED(hr)) {
printf("Failed to call IStream::SetSize\n");
} else {
printf("IStream::SetSize called successfully\n");
}
VariantClear(&vResult);
pStream->lpVtbl->Release(pStream);
FreeLibrary(hOle32);
}
最后,在主函数中调用该函数:
int main()
{
CoInitialize(NULL);
CallIStreamSetSize();
CoUninitialize();
return 0;
}
这样就可以在纯C中使用DispCallFunc调用IStream::SetSize(0)了。
请注意,以上代码仅供参考,实际使用时需要根据具体情况进行适当的修改和错误处理。
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