使用 IL2CPP 脚本后端时,可将 C++ (.cpp) 代码文件直接添加到 Unity 项目中。这些 C++ 文件将充当 Plugin Inspector 中的插件。如果将 C++ 文件配置为与 macOS 播放器兼容,则 Unity 会将这些文件与从托管程序集生成的 C++ 代码一起编译。在 Inspector 窗口的 Platform settings 部分中选择适当的 Mac OS 选项:
因为函数与生成的 C++ 代码链接在一起,所以没有单独的 DLL 可进行 _P/Invoke
调用。因此,可使用"__Internal"
关键字代替 DLL 名称,从而使 C++ 链接器负责解析函数,而不是在运行时加载函数,如下例所示:
[DllImport("__Internal")]
private static extern int
CountLettersInString([MarshalAs(UnmanagedType.LPWSTR)]string str);
可在 NativeFunctions.cpp 中定义此类函数,如下所示:
extern "C" __declspec(dllexport) int __stdcall CountLettersInString(wchar_t* str)
{
int length = 0;
while (*str++ != nullptr)
length++;
return length;
}
因为由链接器负责解析函数调用,所以在托管端的函数声明(即在托管运行时执行的 C# 代码)中发生的任何错误都会生成链接器错误而不是运行时错误。这也意味着,在运行时不需要进行动态加载,而直接从 C# 调用函数。这种方式显著降低了 P/Invoke
调用的性能开销。
• 2018–03–13 页面已发布
2018.1 中的新功能 NewIn20181
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