Re: [PATCH] Apply pattern-matching immediately beneath the stow directory.

[Carl Fredrik Hammar]

Hi,

On Mon, Sep 07, 2009 at 11:24:48PM +0300, Sergiu Ivanov wrote:
> unionfs needs to explicitly enumerate the contents of a directory to
> do pattern matching in it.  I cannot envision a way to do
> multi-component pattern matching without iterating all subdirectories
> of stow/ .  Well, okay, there could be done some optimization (like
> counting the number of components in the pattern and not going deeper
> than that), but it does not change the concept considerably.

> BTW, the implied asterisk in the original implementation is achieved
> by explicitly going down to the second level under stow/ , i.e. it is
> hard-coded in the algorithm, not some patterns, filenames or anything
> else.  Since this implementation didn't care about multi-component
> pattern, I chose not to think of them either.
> 
> Do you have some general idea of how multi-component pattern matching
> could be implemented more efficiently than that?  Some vague pointer
> should suffice for me to adapt the idea to unionfs.

How about matching one component at a time?

For instance, given `*/*/*' you iterate through all files in the
current directory and find matches to `*/' (the slash filters out
non-directories).  For each match you recurse, making the match the
current directory and with the pattern with the tested component removed,
e.g. `*/*'.  The recursion continues until the pattern is static or
there are no matches.

(Clarification: by current directory I don't mean the process' CWD,
just the directory currently being iterated.)

Regards,
  Fredrik