On Sat, 27 May 2017, Yuri Khan wrote:

> On Fri, May 26, 2017 at 8:02 PM, Tino Calancha <tino.calancha@gmail.com> wrote:
>
>> New library implementing a Dired interface for `du'.
>
> That sounds great.
>
>> I)
>> This library defines a minor mode `dired-du-mode' to display
>> the recursive size of directories in Dired buffers.  This mode
>> uses the external `du' program when available.  Otherwise, it
>> performs a rough estimation with Lisp.
>
> Would it be useful to extract the Lisp replacement of du as a separate
> library, or does that raise too many questions about cache management?
That part is expected to be very slow.  I just added recently as a 
fallback, but it is not the recomended way.  Actually I show one 
warning encouraging the user to install `du'.
>
>> II)
>> In addition, this file provides a command `dired-du-count-sizes',
>> to show the total size of the marked files.  By default, it shows
>> the size of the files marked with `dired-marker-char'.   If `dired-du-mode'
>> is disabled, then ignores the size of directories.  Otherwise, it takes
>> in account the size of the dirs.
>> When called with a prefix prompts for the marks and asks if the dirs must
>> be taken in account.
>>
>> ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
>> The file is available for inspection in the following Elpa repo. branch:
>> scratch/dired-du
>
> You are caching directory information in a buffer-local variable
> ‘dired-du-dir-info’. A single Dired buffer can show multiple
> directories, and it can be killed and re-opened. Wouldn’t it make
> sense to share the cache across all Dired buffers and persist it
> independently of buffer lifetimes?
I don't know.  I decided the implementation according with my 
use case:
i just wanted to see the actual size of my dirs in human readable units. 
For this naive purpose the buffer locallity of `dired-du-dir-info' is 
fine.
Once other people start using the lib we might find convenient to change
those particular aspects of the implementation.

> From experience with other file managers implementing directory size
> calculation, it is useful to have a command that recalculates the
> sizes of marked subdirectories, or the subdirectory at point, if none
> are marked. (Their cached size should be discarded and replaced with
> the newly calculated one.)
Good idea.  I just added the command `dired-du-update-dir-info' for
that operation.
Thank you.
>
> Also, you are defining many functions that are copies of dired’s but
> with added functionality. Would it be better to improve dired’s
> functions instead?
Of course it would.
If the lib is ported to master branch, some parts of the lib will be 
absorbed by dired.el, dired-aux.el, dired-x.el, and the file will be
much shorter.
On the other hand, one of the nice things about Elpa is that you can 
support older Emacs.  This file works for Emacs >= 24.4.