Checking wrong UTF-16 names in Windows

checking_wrong_utf16_windows_main.cpp

#include <assert.h>
#include <string>
#include <Windows.h>

std::string utf16ToUtf8(const std::wstring& utf16) {
    int size = WideCharToMultiByte(CP_UTF8, 0, utf16.data(), static_cast<int>(utf16.size()), NULL, 0, NULL, NULL);
    std::string utf8(size, 0x00);
    WideCharToMultiByte(CP_UTF8, 0, utf16.data(), static_cast<int>(utf16.size()), &utf8[0], size, NULL, NULL);
    return utf8;
}

std::wstring utf8ToUtf16(const std::string& utf8) {
    int size = MultiByteToWideChar(CP_UTF8, 0, utf8.data(), static_cast<int>(utf8.size()), NULL, 0);
    std::wstring utf16(size, 0x00);
    MultiByteToWideChar(CP_UTF8, 0, utf8.data(), static_cast<int>(utf8.size()), &utf16[0], size);
    return utf16;
}

int main() {
    std::wstring original_utf16 = { 0xDCA9, 0x2E, 0x74, 0x78, 0x74, 0x00 };

    // Creating the file with non-valid surrogate pair
    HANDLE handle = CreateFileW(original_utf16.c_str(), GENERIC_WRITE, 0, NULL, CREATE_NEW, FILE_ATTRIBUTE_NORMAL, NULL);
    if (handle == INVALID_HANDLE_VALUE) {
        return 1;
    }

    CloseHandle(handle);

    // Converting to UTF-8 and back
    std::string utf8 = utf16ToUtf8(original_utf16);
    std::wstring utf16 = utf8ToUtf16(utf8);

    // Trying to open the file
    handle = CreateFileW(utf16.c_str(), GENERIC_READ, 0, NULL, OPEN_EXISTING, 0, NULL);
    if (handle == INVALID_HANDLE_VALUE) {
        assert(original_utf16 == utf16);
        return 1; // Will here
    }

    CloseHandle(handle);
    return 0;
}