将BSTR转换为const char*

#include <iostream>
#include <Windows.h>

const char* BSTRToConstChar(BSTR bstr)
{
    const char* result = nullptr;

    // 获取BSTR的长度
    int length = SysStringLen(bstr);

    // 分配内存并将BSTR转换为宽字符数组
    wchar_t* wideStr = new wchar_t[length + 1];
    wcscpy_s(wideStr, length + 1, bstr);

    // 获取多字节字符数组的长度
    int mbLength = WideCharToMultiByte(CP_UTF8, 0, wideStr, -1, nullptr, 0, nullptr, nullptr);

    // 分配内存并将宽字符数组转换为多字节字符数组
    char* mbStr = new char[mbLength];
    WideCharToMultiByte(CP_UTF8, 0, wideStr, -1, mbStr, mbLength, nullptr, nullptr);

    // 将多字节字符数组的指针赋值给const char*类型的变量
    result = mbStr;

    // 释放内存
    delete[] wideStr;

    return result;
}

int main()
{
    BSTR bstr = SysAllocString(L"Hello, World!");

    const char* str = BSTRToConstChar(bstr);

    std::cout << str << std::endl;

    // 释放内存
    delete[] str;
    SysFreeString(bstr);

    return 0;
}