Copy a folder programmatically without resolving hardlinks in Windows (Win32 API)

I want to copy an entire folder without resolving the hardlinks

example:

Folder1
  |
  +---File1
      File2
      HardLink3 -> File3

(HardLink3 created using fsutil hardlink create or mklink)

I want to copy this folder to

Folder2
  |
  +---File1
      File开发者_C百科2
      HardLink3 -> File3

keeping Folder2\HardLink3 as a hardlink pointing to File3

Is there an Win32 API call to copy a entire folder with this semantic, or, if I need to do CopyFile / CreateHardLink file by file, what's the API call to check if a given file is a hardlink or not?

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If you're absolutely sure that this is what you want to do, the easiest way to determine whether a file has multiple links (i.e., "is a hard link") is probably GetFileInformationByHandle.

The nNumberOfLinks value returned will be 1 for a normal file and more than 1 if the file is (or has) a hard link.

If I've understood your scenario correctly, it might be more sensible to check whether a file is hard linked to one of a specific set of files (the files in the "shared folder") rather than whether it is hard linked to any file anywhere. To do this, look at the File ID (nFileIndexHigh and nFileIndexLow) which for a hard link is the same as for the original file.

In the latter case, as an optimization you could use GetFileInformationByHandleEx with the FileIdBothDirectoryInfo option to read the names and file IDs for all the files in a given directory in a single operation.

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I do not think there is a Win32 API call to do what you want all in one go, so you probably need to do this by hand.

Checking if a file is a hard-link or not is probably not what you want to do. If a file is not a symbolic link, directory (or reparse point or some other obscure thing) it is actually a hard link, i.e. the name of the file points to a stored file on disk. So if two files are pointing to the same data they are both hard links to that file.

Anyway, the Win32 methods to enumerate all hard links to a file are FindFirstFileNameW and FindNextFileNameW.