Re: [Boost-users] list all drives

Subject: Re: [Boost-users] list all drives
From: John Dlugosz (JDlugosz_at_[hidden])
Date: 2010-07-12 15:31:40

> Windows (AFAIK) does not - all the devices/drives are separate.
> 
> -- Marshall

Since you mentioned "AFAIK", I thought I'd fill in some more details.

The Win32 API has separate roots, using letters and @.
The underlying "native" OS uses a common root for named OS objects that includes files and many other things.  The Win32 function you call takes care of qualifying names that are relative to a current directory and/or drive, and also takes care of drive letters, turning it into a full Native name.  The drive letters are named symbolic links in a known place which seems to vary with Windows versions.  In XP-64-bit, I see "\GLOBAL??" containing "A:" as a link to "\Device\Floppy0", etc.  The "\Device" stuff is not accessible to Win32, but to drivers.  It is like the Unix device directory, except it doesn't make it look like files in a file system.  It's a tree of heterogeneous objects.

Now, you can bypass the parsing done by Win32 and use a file name like "\\?\D:\foo\bar.txt".  In other words, you _can_ start directly at the place where devices are specified.  This same syntax is used for UNC names in the form "\\Server\share\...", so you can treat everything as a single root in windows where that root is "\\" and the local machine is "?\".  This lets you specify devices with GUIDs as well as their assigned drive letters.

--John




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