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/

☄

Xah gmail.com> writes:

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'

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 gmail.com>
wrote:

Xah gmail.com> writes:

AFAIK no, may be use some python dictionary and pickle it.

Xah gmail.com> writes:

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)))

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

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

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

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:

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

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

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: