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Does CBFS allow long paths longer than MAX_PATH?

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#29939
Posted: 06/26/2014 07:15:58
by Marek T (Basic support level)
Joined: 06/26/2014
Posts: 4

We are evaluating CBFS and would like to know if it supports long filenames. We would like to browse a remote DMS under a local virtual drive letter.
The folder and filenames and resulting paths in the DMS can get longer than the usual Windows limit (MAX_PATH is 260 characters, even less for folder paths).

Will using CBFS help us overcome this limit?
#29940
Posted: 06/26/2014 07:22:39
by Eugene Mayevski (EldoS Corp.)

CBFS allows this (and those files can be access via special Windows APIs), but many parts of Windows itself and especially Win32 applications won't.


Sincerely yours
Eugene Mayevski
#29941
Posted: 06/26/2014 07:51:21
by Marek T (Basic support level)
Joined: 06/26/2014
Posts: 4

Hi Eugene,
Thank you for the quick answer.

I am familiar with the long paths API and many applications indeed have issues with such paths. So in case using this API is the only way how to achieve long paths support, it is not usable for us.
#29942
Posted: 06/26/2014 08:55:47
by Volodymyr Zinin (EldoS Corp.)

Actually a "usual" win32 API (like CreateFile) can work with long file names. It's just required to add the "\\?\" prefix to file path. And it's Windows itself not CBFS limits file paths to the MAX_PATH size if there is not such prefix.

Quote
MarekT wrote:
So in case using this API is the only way how to achieve long paths support, it is not usable for us.

Could you specify a variant that is usable for you?
Thanks.
#29943
Posted: 06/26/2014 09:03:36
by Marek T (Basic support level)
Joined: 06/26/2014
Posts: 4

Paths created with the \\?\ prefix cannot be properly opened in many programs, including MS Office. These can usually be browsed with Explorer.

I realize this is not CBFS limitation but rather Windows which cannot be easily worked around.

Quote
Could you specify a variant that is usable for you?

The requirement is to be able to browse the full DMS folder tree (which gets over the MAX_PATH limit quickly) and open files on demand, including those which have paths longer than MAX_PATH. The files should not be downloaded while the user is browsing the DMS, but should be downloaded only "on demand" (before the user opens the file).

Is there an alternative solution to this problem that would provide access to files which would normally map to long paths?
#29944
Posted: 06/26/2014 09:08:54
by Eugene Mayevski (EldoS Corp.)

You can expose different branches as different virtual disks or you can in some way shorten long names of folders when exposing them via the virtual drive, thus making paths shorter. But potentially the limit can be exceeded anyway.


Sincerely yours
Eugene Mayevski
#29945
Posted: 06/26/2014 09:18:03
by Marek T (Basic support level)
Joined: 06/26/2014
Posts: 4

Thank you for the folder name shortening suggestion, we will evaluate this option.

Is the rest of our requirements doable with CBFS?

Can we just "display" the remote files in folders within virtual disks and download them only at the time the user is opening them, or will Windows Explorer itself request the file contents to be downloaded in a way indiscernible from the case when e.g. Word is opening and reading the file?
#29946
Posted: 06/26/2014 11:08:01
by Volodymyr Zinin (EldoS Corp.)

Quote
MarekT wrote:
Is the rest of our requirements doable with CBFS?

Yes.

Quote
MarekT wrote:
Can we just "display" the remote files in folders within virtual disks and download them only at the time the user is opening them, or will Windows Explorer itself request the file contents to be downloaded in a way indiscernible from the case when e.g. Word is opening and reading the file?

You can just display/enumerate file names and download them when their content is requested to read. But quite often Explorer tries to read part of file data to show file icons, etc. Also some third-party software, like antiviruses, can read files.
In order to minimize such data reading you can either use the network mounting points (it's feature of CBFS which represents virtual disks as "remote" disks) or mark files with FILE_ATTRIBUTE_OFFLINE. I don't know all details how the second variant works, but several customers uses such technique.
Also by EldoS: BizCrypto
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