AW: Can't interrupt directory_files_internal run fromtimer-event-handler

AW: Can't interrupt directory_files_internal run fromtimer-event-handler

[klaus.berndl]

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>>>     There's no need to run any program just to know if a directory is
>>>     empty.  Emacs has primitives which will tell that directly (e.g.,
>>>     file-attributes) and do that faster.
>>> 
>> How do you determine that from file-attributes?  It is not obvious.

>A combination of file-attributes (looking at the number of links) and
>directory-files should do that, I think.

Hmm, maybe i oversee something here - but when you have to call
directory-files - where is the improvement compared to the problem of the OP?
`directory-files' IS the problem....

Ciao,
Klaus

>> You might try to do it from the number of hard links to the directory,
>> which will normally be 2 for an empty directory, since users normally
>> can't create alternate names for a directory.  But isn't it possible
>> for root to create them?

>I'm not an expert on this, but I think it's impossible to create such
>alternate names, since GNU Find uses this fact to detect directories
>with no subdirectories.


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Re: AW: Can't interrupt directory_files_internal run fromtimer-event-handler

[Eli Zaretskii]

> Date: Mon, 8 Aug 2005 13:27:46 +0200
> From: <klaus.berndl@sdm.de>
> Cc: <kzeitler@lucent.com>,
> 	<emacs-devel@gnu.org>
> 
> >A combination of file-attributes (looking at the number of links) and
> >directory-files should do that, I think.
> 
> Hmm, maybe i oversee something here - but when you have to call
> directory-files - where is the improvement compared to the problem of
> the OP?

It's an improvement because (1) directory-files is a direct interface
to system calls, and (2) it is more portable since it does not rely on
the existence of `ls', which is only standard on Posix platforms.

> `directory-files' IS the problem....

Well, I'm sorry if I missed something at the beginning of this thread,
but what problem in directory-files are you talking about?

AW: Can't interrupt directory_files_internal run fromtimer-event-handler

[klaus.berndl]

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>> ECB encapslates ist "stealthy" tasks in a loop like:

>>         (while (and (not (input-pending-p))
>>                 ...

>> So IMHO C-g should work....

>Only if each iteration takes a (small) finite time.  The OP's problem is
>that one of the iteration doesn't terminate.

i know - therefore my question concerning while-no-input!
In fact: ECB has some tasks which should be run really(!) stealthy, like
checking if a dir is empty, getting the VC-state of all files in a dir,
checking which files in a dir are read-only... in case of a remote host
an iteration of such a task (i.e. for one file of a dir) can be potentially
long lasting...

With the current available elisp-tools (macos, functions etc.) ECB can run
these tasks only pseudo-stealthy...therefore a way to make this really stealthy
would be very important for ECB so users are not blocked...

I have no preference how to achieve this (while-no-input, with-local-quit etc..),
but i would be great if i could achieve this goal at all!

>> AFAIK there is a new macro in CVS named `while-no-input' (there
>> was a discussion some time ago).... Could using this macro
>> solve problems like that posted from the OP??

>Could be.  Another related new macro is with-local-quit (which uses no new
>internal feature and can thus be backported to other Emacsen).

see above - what would be the best way to enable real stealthiness?

Thanks a lot,
Klaus

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Re: AW: Can't interrupt directory_files_internal run fromtimer-event-handler

[Richard M. Stallman]

    In fact: ECB has some tasks which should be run really(!) stealthy, like
    checking if a dir is empty, getting the VC-state of all files in a dir,
    checking which files in a dir are read-only... in case of a remote host

The best way to do this and make sure it is stealthy is by running a
subprocess.  The subprocess can run in parallel with Emacs.

AW: Can't interrupt directory_files_internal run fromtimer-event-handler

[klaus.berndl]

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>> With the current available elisp-tools (macos, functions etc.) ECB can run
>> these tasks only pseudo-stealthy...therefore a way to make this really
>> stealthy would be very important for ECB so users are not blocked...

>> I have no preference how to achieve this (while-no-input, with-local-quit
>> etc..), but i would be great if i could achieve this goal at all!

>Do you expect us to figure out what's best for you?

no

>I'd say use while-no-input but you're in a better position to make this call.

the only thing i wanted is: An expert-estimation if while-no-input is a good
way - or with-local-quit - if i remember right you said that this could
easily being backported - maybe its not a really good idea to use a macro
which is only available in forthcoming Emacs 22 - IMHO also users of Emacs 21.X
should get a good solution...

is there a short example how to use this with-local-quit? This would help me
a lot - or a pointer where to find such an example..

Thanks for your help,
Klaus


        Stefan


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Re: Can't interrupt directory_files_internal run fromtimer-event-handler

[Stefan Monnier]

>> I'd say use while-no-input but you're in a better position to make this call.

> the only thing i wanted is: An expert-estimation if while-no-input is
> a good way - or with-local-quit - if i remember right you said that this
> could easily being backported - maybe its not a really good idea to use
> a macro which is only available in forthcoming Emacs 22 - IMHO also users
> of Emacs 21.X should get a good solution...

while-no-input is a more general and robust way to do what your (while (not
(input-pending-p))) is trying to do.  It's basically designed specifically
for cases like yours.  But it's a new feature in Emacs-22.

with-local-quit is just a convenient macro to temporarily disable
inhibit-quit (that's typically set in timers, post-command-hooks, ...).
The macro-expanded code doesn't use any new feature.  It's not a general
solution to your problem, but it can be used to solve the specific problem
of the OP where C-g wasn't able to unfreeze Emacs.

> is there a short example how to use this with-local-quit? This would help me
> a lot - or a pointer where to find such an example..

cd ...emacs/lisp; grep with-local-quit **/*.el

Read the definition of the macro: it's fairly simple.


        Stefan