在 Windows 中，除了可移植性之外，我应该使用 CreateFile 还是 fopen？

发布于 2024-09-05 09:34:10 字数 41 浏览 7 评论 0 原文

有哪些差异，在什么情况下其中一个或另一个在某种程度上会被证明更优越？

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梦晓ヶ微光ヅ倾城 2024-09-12 09:34:10

首先，函数fopen只能用于对文件进行简单的可移植操作。

另一端的CreateFile不仅可以用于对文件的操作，还可以用于对目录（使用相应选项）、管道和各种Windows设备的操作。

CreateFile 有很多其他有用的开关，例如 FILE_FLAG_NO_BUFFERING、FILE_ATTRIBUTE_TEMPORARY 和 FILE_FLAG_SEQUENTIAL_SCAN，它们在不同的场景。

您可以将 CreateFile 与文件名长度超过 MAX_PATH 个字符的文件一起使用。对于某些服务器应用程序或必须能够打开任何文件的应用程序（例如病毒扫描程序或备份应用程序）来说，这可能很重要。这是通过使用命名空间语义来实现的，尽管此模式有其自身的问题，例如实际创建名为 ".." 或 L"\xfeff\x20\xd9ab" （祝你稍后尝试删除它们好运）。

您可以在不同的安全场景中使用CreateFile。我的意思不仅仅是安全属性的使用。如果当前进程具有 SE_BACKUP_NAME 或 SE_RESTORE_NAME 权限（管理员通常拥有的权限）并启用此权限，则可以使用 CreateFile 打开任何文件，也可以是您无权访问的文件通过安全描述符。

如果您只想读取文件的内容，可以使用CreateFile、CreateFileMapping和MapViewOfFile来创建文件映射。然后，您可以像处理内存块一样处理文件，这可能会提高应用程序的速度。

该函数还有其他用途，在相应的 MSDN 文章。

所以我可以总结一下：仅当您有硬可移植性要求或者需要将 FILE* 传递给某些外部时库，那么你必须使用fopen。在所有其他情况下，我建议您使用CreateFile。
为了获得最佳结果，我还建议专门学习 Windows API，因为您可以找到很多有用的功能。

更新：与您的问题没有直接关系，但我也建议您看一下事务性 I/O 功能。使用此功能，您可以将一系列文件、目录或注册表操作作为一个不可中断的事务提交。这是一个非常强大且有趣的工具。如果您现在还没有准备好使用事务性 I/O 函数，则可以从 CreateFile 开始，稍后将应用程序移植到事务性 I/O。

First of all the function fopen can be used only for simple portable operations with files.

CreateFile on the other side can be used not only for operations with files, but also with directories (with use of corresponding options), pipes and various Windows devices.

CreateFile has a lot of additional useful switches, like FILE_FLAG_NO_BUFFERING, FILE_ATTRIBUTE_TEMPORARY and FILE_FLAG_SEQUENTIAL_SCAN, which can be very useful in different scenarios.

You can use CreateFile with a filename longer that MAX_PATH characters. It can be important for some server applications or ones which must be able to open any file (a virus scanner or a backup application for example). This is enabled by using namespace semantics, though this mode has its own concerns, like ability to actually create a file named ".." or L"\xfeff\x20\xd9ab" (good luck trying to delete them later).

You can use CreateFile in different security scenarios. I mean not only usage of security attributes. If current process has SE_BACKUP_NAME or SE_RESTORE_NAME privilege (like Administrators typically have) and enable this privilege, one can use CreateFile to open any file also a file to which you have no access through security descriptor.

If you only want to read the content of a file, you can use CreateFile, CreateFileMapping and MapViewOfFile to create file mapping. Then you can work with a file as with a block of memory, which can possibly increase your application's speed.

There are also other uses of the function, which are described in detail in the corresponding MSDN article.

So I can summarize: only if you have a hard portability requirements or if you need to pass a FILE* to some external library, then you have to use fopen. In all other cases I would recommend you to use CreateFile.
For best results, I would also advise to learn Windows API specifically, as there are many features that you can find a good use for.

UPDATED: Not directly related to your question, but I also recommend you to take a glance at transactional I/O functions which are supported starting with Windows Vista. Using this feature, you can commit a bunch of operation with files, directories or registry as one transaction that cannot be interrupted. It is a very powerful and interesting tool. If you are not ready now to use the transactional I/O functions, you can start with CreateFile and port your application to transactional I/O later.