print hash table to disk and reread in hash table

print hash table to disk and reread in hash table

[Xah]

if i have a hash table in elisp, is there a way to save it to disk and
reread in when starting emacs?

Thanks.

  Xah
∑ http://xahlee.org/

☄

Re: print hash table to disk and reread in hash table

[Thierry Volpiatto]

Xah <xahlee@gmail.com> writes:

> if i have a hash table in elisp, is there a way to save it to disk and
> reread in when starting emacs?
What you can do is creating a named hash-table at each time you start
emacs and load a file containing (puthash that...) (puthash this...)
etc... Here an example of one of my files:

,----
| ;;; dvc-bookmarks-cache -*- mode: emacs-lisp; coding: utf-8; -*-
| (puthash 'MAIL '((color . dvc-excluded) (state . "open") (time-stamp . "2008.06.23")) dvc-bookmarks-cache)
| (puthash 'CONFIG '((color . dvc-source) (state . "open") (time-stamp . "2008.06.23")) dvc-bookmarks-cache)
| (puthash 'DVC '((color . dvc-mark) (state . "open") (time-stamp . "2008.08.15")) dvc-bookmarks-cache)
| (puthash 'SOURCES '((color . dvc-unknown) (state . "open") (time-stamp . "2008.06.23")) dvc-bookmarks-cache)
`----

The hash-table here is `dvc-bookmark-cache'

-- 
A + Thierry Volpiatto
Location: Saint-Cyr-Sur-Mer - France

Re: print hash table to disk and reread in hash table

[Xah]

but is there a function or lib to save hashtable to disk? i.e.
sometimes called serializing?

  Xah
∑ http://xahlee.org/

☄

On Aug 27, 10:21 pm, Thierry Volpiatto <thierry.volpia...@gmail.com>
wrote:
> Xah <xah...@gmail.com> writes:
> > if i have a hash table in elisp, is there a way to save it to disk and
> > reread in when starting emacs?
>
> What you can do is creating a named hash-table at each time you start
> emacs and load a file containing (puthash that...) (puthash this...)
> etc... Here an example of one of my files:
>
> ,----
> | ;;; dvc-bookmarks-cache -*- mode: emacs-lisp; coding: utf-8; -*-
> | (puthash 'MAIL '((color . dvc-excluded) (state . "open") (time-stamp . "2008.06.23")) dvc-bookmarks-cache)
> | (puthash 'CONFIG '((color . dvc-source) (state . "open") (time-stamp . "2008.06.23")) dvc-bookmarks-cache)
> | (puthash 'DVC '((color . dvc-mark) (state . "open") (time-stamp . "2008.08.15")) dvc-bookmarks-cache)
> | (puthash 'SOURCES '((color . dvc-unknown) (state . "open") (time-stamp . "2008.06.23")) dvc-bookmarks-cache)
> `----
>
> The hash-table here is `dvc-bookmark-cache'
>
> --
> A + Thierry Volpiatto
> Location: Saint-Cyr-Sur-Mer - France

Re: print hash table to disk and reread in hash table

[Thierry Volpiatto]

Xah <xahlee@gmail.com> writes:

> but is there a function or lib to save hashtable to disk? i.e.
> sometimes called serializing?
AFAIK no, may be use some python dictionary and pickle it.

>   Xah
> ∑ http://xahlee.org/
>
> ☄
>
> On Aug 27, 10:21 pm, Thierry Volpiatto <thierry.volpia...@gmail.com>
> wrote:
>> Xah <xah...@gmail.com> writes:
>> > if i have a hash table in elisp, is there a way to save it to disk and
>> > reread in when starting emacs?
>>
>> What you can do is creating a named hash-table at each time you start
>> emacs and load a file containing (puthash that...) (puthash this...)
>> etc... Here an example of one of my files:
>>
>> ,----
>> | ;;; dvc-bookmarks-cache -*- mode: emacs-lisp; coding: utf-8; -*-
>> | (puthash 'MAIL '((color . dvc-excluded) (state . "open") (time-stamp . "2008.06.23")) dvc-bookmarks-cache)
>> | (puthash 'CONFIG '((color . dvc-source) (state . "open") (time-stamp . "2008.06.23")) dvc-bookmarks-cache)
>> | (puthash 'DVC '((color . dvc-mark) (state . "open") (time-stamp . "2008.08.15")) dvc-bookmarks-cache)
>> | (puthash 'SOURCES '((color . dvc-unknown) (state . "open") (time-stamp . "2008.06.23")) dvc-bookmarks-cache)
>> `----
>>
>> The hash-table here is `dvc-bookmark-cache'
>>
>> --
>> A + Thierry Volpiatto
>> Location: Saint-Cyr-Sur-Mer - France
>

-- 
A + Thierry Volpiatto
Location: Saint-Cyr-Sur-Mer - France

Re: print hash table to disk and reread in hash table

[Ted Zlatanov]

On Wed, 27 Aug 2008 22:27:47 -0700 (PDT) Xah <xahlee@gmail.com> wrote: 

X> but is there a function or lib to save hashtable to disk? i.e.
X> sometimes called serializing?

No.  It's easy to convert a hashtable to a list, and Emacs makes it easy
to serialize a list, so that's what people do.  I have code in
gnus-registry.el (copied in part from the way Gnus saves its newsrc
file) to do this.  The combination of two easy things is not,
unfortunately, simple anymore.

I like the (puthash ...) approach suggested by Thierry Volpiatto but
it's a lot of function calls for a large hashtable (which the Gnus
registry creates).  So I'm not sure it's the right approach either.

BBDB has a similar problem; it saves vectors instead of lists.

If there's no library for serialization, it should definitely be
written.  Emacs Lisp has only a few basic data types, and not all of
them have to be supported anyhow.

Ted

Re: print hash table to disk and reread in hash table

[Eli Zaretskii]

> From: Ted Zlatanov <tzz@lifelogs.com>
> Date: Thu, 28 Aug 2008 09:03:53 -0500
> 
> If there's no library for serialization, it should definitely be
> written.

You mean, like bindat.el?

Re: print hash table to disk and reread in hash table

[Ted Zlatanov]

On Thu, 28 Aug 2008 21:10:56 +0300 Eli Zaretskii <eliz@gnu.org> wrote: 

>> From: Ted Zlatanov <tzz@lifelogs.com>
>> Date: Thu, 28 Aug 2008 09:03:53 -0500
>> 
>> If there's no library for serialization, it should definitely be
>> written.

EZ> You mean, like bindat.el?

That looks useful for binary data.  I don't see from the code how to use
it to save and load a hashtable.  The spec format supports these types:

;; TYPE    ::= ( eval EXPR )		-- interpret result as TYPE
;;	    |  u8   | byte		-- length 1
;;          |  u16  | word | short      -- length 2, network byte order
;;          |  u24                      -- 3-byte value
;;          |  u32  | dword | long      -- length 4, network byte order
;;          |  u16r | u24r | u32r       -- little endian byte order.
;;	    |  str LEN                  -- LEN byte string
;;          |  strz LEN                 -- LEN byte (zero-terminated) string
;;          |  vec LEN [TYPE]           -- vector of LEN items of TYPE (default: u8)
;;          |  ip                       -- 4 byte vector
;;          |  bits LEN                 -- List with bits set in LEN bytes.

Is there some magic with `eval'?  I didn't get it.

In addition, this library doesn't manage file I/O.  I'd expect the
library do do content coding and error handling internally.  This is,
actually, the most tedious part.  Transforming a hashtable to a list and
back is easy (even I can write it :)

Ted

Re: print hash table to disk and reread in hash table

[Eli Zaretskii]

> From: Ted Zlatanov <tzz@lifelogs.com>
> Date: Fri, 29 Aug 2008 09:06:02 -0500
> 
> On Thu, 28 Aug 2008 21:10:56 +0300 Eli Zaretskii <eliz@gnu.org> wrote: 
> 
> >> From: Ted Zlatanov <tzz@lifelogs.com>
> >> Date: Thu, 28 Aug 2008 09:03:53 -0500
> >> 
> >> If there's no library for serialization, it should definitely be
> >> written.
> 
> EZ> You mean, like bindat.el?
> 
> That looks useful for binary data.  I don't see from the code how to use
> it to save and load a hashtable.

I never used it, I just advertised the closest hit for what you seemed
to be looking.

> In addition, this library doesn't manage file I/O.  I'd expect the
> library do do content coding and error handling internally.  This is,
> actually, the most tedious part.

A cause for a small project, I guess. ;-)

Re: print hash table to disk and reread in hash table

[Ted Zlatanov]

On Fri, 29 Aug 2008 17:52:07 +0300 Eli Zaretskii <eliz@gnu.org> wrote: 

EZ> You mean, like bindat.el?
>> 
>> That looks useful for binary data.  I don't see from the code how to use
>> it to save and load a hashtable.

EZ> I never used it, I just advertised the closest hit for what you seemed
EZ> to be looking.

>> In addition, this library doesn't manage file I/O.  I'd expect the
>> library do do content coding and error handling internally.  This is,
>> actually, the most tedious part.

EZ> A cause for a small project, I guess. ;-)

I can just copy the code out of gnus-registry.el and abstract the
functionality to do a first cut of such a library.  For a large
hashtable, though, converting to a list on the way in and out is
inefficient compared to storing it in a more "native" format.  Is there
such a format, comparable to the native list read-eval format, as seen
in gnus-load:

  (with-temp-buffer
    (insert-file-contents file)
    (while (not (eobp))
      (condition-case type
	  (let ((form (read (current-buffer))))
	    (eval form))
;; ... much code omitted ...

cc to emacs-devel as I think this is of interest to that list.

Thanks
Ted

Re: print hash table to disk and reread in hash table

[Niels Giesen]

Xah <xahlee@gmail.com> writes:

> if i have a hash table in elisp, is there a way to save it to disk and
> reread in when starting emacs?
>
> Thanks.
>
>   Xah
> ∑ http://xahlee.org/
>
> ☄

You might use this code (I use it in gimp-mode):

(defmacro gimp-hash-to-list (hash-table)
  (let ((nl (gensym)))
    `(let (,nl)
       (maphash (lambda (k v)
                  (push (list k v) ,nl)) ,hash-table)
       ,nl)))

(defmacro gimp-list-to-hash (list)
  (let ((ht (gensym)))
    `(let ((,ht (make-hash-table)))
       (mapc (lambda (item)
               (puthash (car item) (cadr item) ,ht)) ,list)
       ,ht)))

Re: print hash table to disk and reread in hash table

[harven]

Xah <xahlee@gmail.com> writes:

> if i have a hash table in elisp, is there a way to save it to disk and
> reread in when starting emacs?

You can try to convert the hash table to an alist using
gnus-hashtable-to-alist, save the alist somewhere, then read it back
at startup using gnus-alist-to-hashtable. These functions come from
gnus, the emacs mailreader, which ships with a basic emacs install.