[boost] Re: Filesystem portable path rationale and use-cases

From: David Abrahams (dave_at_[hidden])
Date: 2003-08-20 08:15:09

Walter Landry <wlandry_at_[hidden]> writes:

> David Abrahams <dave_at_[hidden]> wrote:
>> Walter Landry <wlandry_at_[hidden]> writes:
>> 
>> > Brian Gray <briangray_at_[hidden]> wrote:
>> >> Should we (do we?) have some spreadsheet enumerating various filesystem 
>> >> features, quirks, and limitations for whatever systems we can find, and 
>> >> using that as a reference regarding how to organize features like 
>> >> paths, file references, forks, or whatever else?  It might help us to 
>> >> back out of the code and re-examine the problem domain regardless of 
>> >> the current state of Boost.
>> >
>> > I've been thinking that maybe the best way to provide for portable
>> > paths is to have a bunch of flags that you can set.  So when you push
>> > something onto Beman's singleton stack, you can, for example, set the
>> > NTFS and VMS flags if you only care about those filesystems.
>> >
>> > However, that makes it difficult to extend to customized portability
>> > restrictions.  That might require some kind of function stack within
>> > each element of the singleton stack.  Then you can push the NTFS and
>> > VMS checkers onto that stack within the stack.
>> 
>> I _really_ hope we don't have any singleton stack which affects path
>> validation.  It sounds like a nightmare for any application involving
>> threads.
>
> I think I finally understand what the problems with multiple threads
> are.  You are worried that one thread's portability checking will be
> changed midstream by another thead.  Sounds hairy.  So one solution is
> to make the portability checking local to a thread.  I don't have a
> feel for how to implement that

You'd need TLS, IIUC a limited resource that I wouldn't want to spend
on this.

> and it does seem to introduce complexity where it isn't always
> needed.

Absolutely; IMO the whole issue of "portable" representations and
portability checking needs to be rethought in the context of use
cases.  I do believe there's a satisfactory simple approach in there
somewhere.

-- 
Dave Abrahams
Boost Consulting
www.boost-consulting.com