Question

我正在尝试找出一些COM编组功能。最终，我想将深度嵌套的变量数组持久化到文件中，但是我首先尝试使用一个简单的字符串。我意识到这些API是用于远程过程调用的，但是我希望这种序列化也适合文件持久化。

我使用Excel VBA进行了大量工作，发现这种序列化API确实令人大开眼界。

下面的代码将BSTR序列化到缓冲区，缓冲区被复制，这将替代保存到文件或从文件中加载。

当前问题是BSTR_UserUnmarshal引发异常Unhandled exception at 0x7631C762 (KernelBase.dll) in RPCMarshalling.exe: 0x00000057: The parameter is incorrect. occurred

我可能语法错误，因为我正在处理示例代码片段。目的是通过RPC序列化API调用将字符串从srctest转换为desttest。

// RPCMarshalling.cpp : This file contains the 'main' function. Program execution begins and ends there.
//

#include "pch.h"
#include <iostream>

//https://searchcode.com/file/140723732/dlls/oleaut32/tmarshal.c#l-818

typedef struct _marshal_state {
    LPBYTE  base;
    int     size;
    int     curoff;
} marshal_state;


int main()
{
    ::CoInitialize(0);

    CComBSTR srctest("Hello");
    marshal_state srcbuf;
    memset(&srcbuf, 0, sizeof(srcbuf));
    ULONG flags = MAKELONG(MSHCTX_DIFFERENTMACHINE, NDR_LOCAL_DATA_REPRESENTATION);

    ULONG size = ::BSTR_UserSize(&flags, 0, &srctest);

    DWORD newsize = max(size, 256);
    (&srcbuf)->base = (LPBYTE)HeapAlloc(GetProcessHeap(), HEAP_ZERO_MEMORY, newsize);
    if (!(&srcbuf)->base)
        return E_OUTOFMEMORY;

    ::BSTR_UserMarshal(&flags, (&srcbuf)->base + (&srcbuf)->curoff, &srctest);
    (&srcbuf)->curoff = size;


    std::cout << "Hello World!\n" << size << "\n";


    marshal_state destbuf;
    memset(&destbuf, 0, sizeof(destbuf));

    (&destbuf)->base = (LPBYTE)HeapAlloc(GetProcessHeap(), HEAP_ZERO_MEMORY, newsize);
    if (!(&destbuf)->base)
        return E_OUTOFMEMORY;

    /* pretend we are loading from file saved by src buffer */
    RtlCopyMemory((&destbuf)->base, (&srcbuf)->base, newsize);


    CComBSTR desttest("");
    BSTR deststring;

    try
    {
        unsigned char *buffer;
        buffer = ::BSTR_UserUnmarshal(&flags, (&destbuf)->base, &deststring);
    }
    catch (int e)
    {
        std::cout << "Error:" << e << "\n" << size << "\n";
    }



    ::CoUninitialize();

}

Answer 1

使用西蒙·穆里尔（Simon Mourier）关于StgSerializePropVariant的建议，实现序列化Variant（按照OP的问题文本）工作的目标的另一种方法

int main()
{
    ::CoInitialize(0);

    CComVariant srctest("Hello");

    SERIALIZEDPROPERTYVALUE* serialized;
    ULONG cb;
    ::StgSerializePropVariant((PROPVARIANT*)&srctest, &serialized, &cb);

    CComVariant pvDest;
    ::StgDeserializePropVariant(serialized, cb, (PROPVARIANT*)&pvDest);

    CoTaskMemFree(serialized);

    CComBSTR strDest(pvDest.bstrVal);
    std::cout << "This got serialized:\n" << LPCSTR(_bstr_t(strDest, true)) << "\n";

    ::CoUninitialize();
}

Answer 2

实际上，如果目标是序列化，那么为什么不序列化到IStream

int main()
{
    ::CoInitialize(0);

    CComVariant srctest("Hello");

    CComPtr<IStream> pStream;
    HRESULT hr;
    hr = CreateStreamOnHGlobal(NULL, TRUE,(LPSTREAM *) &pStream.p);
    if (hr != S_OK) return hr;

    hr = srctest.WriteToStream(pStream, VT_BSTR);
    if (hr != S_OK) return hr;

    {
        // stream needs resetting to the start before we 
        // attempt to read it
        LARGE_INTEGER  dlibMove;
        dlibMove.HighPart = 0;
        dlibMove.LowPart = 0;
        DWORD dwOrigin;
        dwOrigin = 0;
        ULARGE_INTEGER  libNewPosition;
        hr = pStream->Seek(dlibMove, dwOrigin, &libNewPosition);
        if (hr != S_OK) return hr;
    }

    CComVariant pvDest;
    hr = pvDest.ReadFromStream(pStream, VT_BSTR);
    if (hr != S_OK) return hr;

    CComBSTR strDest(pvDest.bstrVal);
    std::cout << "This got serialized:\n" << LPCSTR(_bstr_t(strDest, true)) << "\n";
    //std::cout << "This got serialized:\n" << strDest.m_str << "\n";

    ::CoUninitialize();
}

如何序列化VARIANT或BSTR？

2 个答案: