c# - 通过 Pinvoke 传递 C# 字符串

Question

C# 端:

    [DllImport(@"FileGuidUtils.dll", CallingConvention = CallingConvention.Cdecl, CharSet = CharSet.Unicode)]
    private static extern long getReparseType([MarshalAsAttribute(UnmanagedType.LPWStr)] string linkPath);

C/C++ 方面:

__declspec(dllexport) ReparseType getReparseType(WCHAR *linkPath) {
    HANDLE hFile = CreateFile(linkPath, GENERIC_ALL, FILE_SHARE_READ | FILE_SHARE_WRITE, NULL, OPEN_EXISTING, FILE_FLAG_BACKUP_SEMANTICS | FILE_FLAG_OPEN_REPARSE_POINT, NULL);
    if (hFile == INVALID_HANDLE_VALUE)
    {
        CloseHandle(hFile);
        return NEITHER;
    }

    REPARSE_DATA_BUFFER *reparseDataBuffer = (REPARSE_DATA_BUFFER *)malloc(MAXIMUM_REPARSE_DATA_BUFFER_SIZE);
    DWORD dwRetLen = 0;
    BOOL bRet = DeviceIoControl(hFile, FSCTL_GET_REPARSE_POINT, NULL, 0, reparseDataBuffer, MAXIMUM_REPARSE_DATA_BUFFER_SIZE, &dwRetLen, NULL);
    if (bRet == FALSE)
    {
        free(reparseDataBuffer);
        CloseHandle(hFile);
        return NEITHER;
    }

    ULONG reparseType = reparseDataBuffer->ReparseTag;
    free(reparseDataBuffer);
    CloseHandle(hFile);

    if (reparseType == IO_REPARSE_TAG_SYMLINK) {
        return SYMLINK;
    }
    else if (reparseType == IO_REPARSE_TAG_MOUNT_POINT) {
        return JUNCTION;
    }

    return NEITHER;
}

linkPath是如何传递的？它是作为 malloc 字符串传递的，我需要在 C/C++ 端释放它，还是 CLR 会为我处理它？如果它正在清理，我是否正确传递了它？我可以将它作为普通的 C# 字符串传递，而不使用 [MarshalAsAttribute(UnmanagedType.LPWStr)] 吗？谢谢!

Answer 1

C# 将为您将 C# 字符串复制到非托管内存中，传递指向它的指针并在函数调用完成后删除该字符串